172 results on '"Fleiss JL"'
Search Results
2. Review papers : The statistical basis of meta-analysis
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Fleiss, JL, primary
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- 1993
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3. The mortality risk associated with digitalis treatment after myocardial infarction
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Linda M. Rolnitzky, Terry M. Therneau, Fleiss Jl, E. Carleen, Odoroff Cl, Bigger Jt, and Arthur J. Moss
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Male ,medicine.medical_specialty ,Myocardial Infarction ,Digitalis ,Risk Factors ,Internal medicine ,medicine ,Hospital discharge ,Humans ,Pharmacology (medical) ,Myocardial infarction ,Survival analysis ,Aged ,Pharmacology ,biology ,Proportional hazards model ,business.industry ,Mortality rate ,Digitalis Glycosides ,General Medicine ,Middle Aged ,biology.organism_classification ,medicine.disease ,Confidence interval ,Relative risk ,Cardiology ,Female ,Cardiology and Cardiovascular Medicine ,business - Abstract
We examined the effects of digitalis therapy on postinfarction mortality throughout a 24-month to 48-month follow-up in 867 patients who survived an acute myocardial infarction. During follow-up, 145 patients died (16.7% mortality). At the time of hospital discharge, 31% of the patients were taking digitalis. The digitalis-treated patients were older, had more medical-cardiac risk factors, and had a higher mortality rate throughout the follow-up than the nondigitalis-treated patients. Statistical techniques were used to adjust for clinical imbalances between the digitalis-treated patients and nondigitalis-treated patients. The survival analysis (n = 728 patients) utilized the Cox regression model, and the digitalis-associated mortality risk was identified only after all significant covariates were allowed, so that mortality could be predicted as accurately as possible. Digitalis therapy was associated with a significantly increased postinfarction mortality risk after adjustment for the predictor covariates (relative risk 2.3, 95% confidence interval 1.4-3.7, p less than 0.001). The findings from this large multicenter study suggest that it would be prudent to exercise caution in the use of digitalis in postinfarction patients.
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- 1987
4. Hormones and sexual orientation in men
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Fleiss Jl, Friedman Rc, Linkie D, Dyrenfurth I, and Tendler R
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Adult ,Male ,Estradiol ,Hydrocortisone ,Estrone ,Sexual Behavior ,Androstenedione ,Estrogens ,Homosexuality ,Luteinizing Hormone ,Developmental psychology ,Psychiatry and Mental health ,Sexual orientation ,Androgens ,Humans ,Testosterone ,Psychology ,Hormone - Published
- 1977
5. Power law behavior of RR-interval variability in healthy middle-aged persons, patients with recent acute myocardial infarction, and patients with heart transplants.
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Bigger JT Jr, Steinman RC, Rolnitzky LM, Fleiss JL, Albrecht P, and Cohen RJ
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- Adult, Humans, Middle Aged, Postoperative Period, Reference Values, Regression Analysis, Electrocardiography, Ambulatory, Heart Transplantation physiology, Myocardial Infarction physiopathology
- Abstract
Background: The purposes of the present study were (1) to establish normal values for the regression of log(power) on log(frequency) for, RR-interval fluctuations in healthy middle-aged persons, (2) to determine the effects of myocardial infarction on the regression of log(power) on log(frequency), (3) to determine the effect of cardiac denervation on the regression of log(power) on log(frequency), and (4) to assess the ability of power law regression parameters to predict death after myocardial infarction., Methods and Results: We studied three groups: (1) 715 patients with recent myocardial infarction; (2) 274 healthy persons age and sex matched to the infarct sample; and (3) 19 patients with heart transplants. Twenty-four-hour RR-interval power spectra were computed using fast Fourier transforms and log(power) was regressed on log(frequency) between 10(-4) and 10(-2) Hz. There was a power law relation between log(power) and log(frequency). That is, the function described a descending straight line that had a slope of approximately -1 in healthy subjects. For the myocardial infarction group, the regression line for log(power) on log(frequency) was shifted downward and had a steeper negative slope (-1.15). The transplant (denervated) group showed a larger downward shift in the regression line and a much steeper negative slope (-2.08). The correlation between traditional power spectral bands and slope was weak, and that with log(power) at 10(-4) Hz was only moderate. Slope and log(power) at 10(-4) Hz were used to predict mortality and were compared with the predictive value of traditional power spectral bands. Slope and log(power) at 10(-4) Hz were excellent predictors of all-cause mortality or arrhythmic death. To optimize the prediction of death, we calculated a log(power) intercept that was uncorrelated with the slope of the power law regression line. We found that the combination of slope and zero-correlation log(power) was an outstanding predictor, with a relative risk of > 10, and was better than any combination of the traditional power spectral bands. The combination of slope and log(power) at 10(-4) Hz also was an excellent predictor of death after myocardial infarction., Conclusions: Myocardial infarction or denervation of the heart causes a steeper slope and decreased height of the power law regression relation between log(power) and log(frequency) of RR-interval fluctuations. Individually and, especially, combined, the power law regression parameters are excellent predictors of death of any cause or arrhythmic death and predict these outcomes better than the traditional power spectral bands.
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- 1996
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6. Vagal modulation of RR intervals during head-up tilt and the infusion of isoproterenol.
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Bloomfield DM, Bigger JT Jr, Pavri BB, Han J, Fleiss JL, Rolnitzky LM, and Steinman RC
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- Adult, Female, Fourier Analysis, Heart drug effects, Humans, Infusions, Intravenous, Isoproterenol administration & dosage, Male, Supine Position, Tilt-Table Test, Electrocardiography, Heart physiology, Isoproterenol pharmacology, Posture, Vagus Nerve physiology
- Abstract
The objective of this study was to characterize the autonomic effects of 2 interventions, head-up tilt and isoproterenol infusion, which alter autonomic balance by different mechanisms but produce the same RR intervals. We compared the effect of head-up tilt with the effect of isoproterenol on autonomic balance as measured by power spectral analysis of RR variability. Fifteen normal subjects had baseline measurements and then underwent head-up tilt. After return to baseline supine values, isoproterenol was infused at a rate of 1 microgram/min (low-dose isoproterenol), which was then increased to 2.1 +/- 0.5 microgram/min (high-dose isoproterenol). All subjects underwent a second tilt during high-dose isoproterenol, and 9 subjects completed this second tilt study. During the experiment, normal RR intervals were recorded and 5-minute segments were used to calculate power spectra. High-frequency (HF) power (0.15 to 0.40 Hz) was used as a measure of vagal activity. The effects of head-up tilt were compared with the effects of low-dose isoproterenol. Despite nearly identical mean RR intervals (784 ms with tilt vs 792 ms with low-dose isoproterenol, p = NS), there was significantly (p < 0.05) less HF power during head-up tilt in the drug-free state (172 ms2) than during low-dose isoproterenol in the supine position (307 ms2). A second head-up tilt was performed during the infusion of high-dose isoproterenol. During high-dose isoproterenol, tilt caused a decrease in RR intervals (from 573 to 491 ms; p < 0.01) and a decrease in HF power (from 68 to 28 ms2; p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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- 1995
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7. RR variability in healthy, middle-aged persons compared with patients with chronic coronary heart disease or recent acute myocardial infarction.
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Bigger JT Jr, Fleiss JL, Steinman RC, Rolnitzky LM, Schneider WJ, and Stein PK
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- Age Factors, Coronary Disease diagnosis, Coronary Disease mortality, Female, Humans, Linear Models, Male, Middle Aged, Myocardial Infarction diagnosis, Myocardial Infarction mortality, Predictive Value of Tests, Reference Values, Risk Factors, Sex Factors, Time Factors, Coronary Disease physiopathology, Electrocardiography, Ambulatory, Heart Rate physiology, Myocardial Infarction physiopathology, Signal Processing, Computer-Assisted
- Abstract
Background: The purpose of this investigation was to establish normal values of RR variability for middle-aged persons and compare them with values found in patients early and late after myocardial infarction. We hypothesized that presence or absence of coronary heart disease, age, and sex (in this order of importance) are all correlated with RR variability., Methods and Results: To determine normal values for RR variability in middle-aged persons, we recruited a sample of 274 healthy persons 40 to 69 years old. To determine the effect of acute myocardial infarction RR variability, we compared measurements of RR variability made 2 weeks after myocardial infarction (n = 684) with measurements made on age- and sex-matched middle-aged subjects with no history of cardiovascular disease (n = 274). To determine the extent of recovery of RR variability after myocardial infarction, we compared measurements of RR variability made in the group of healthy middle-aged persons with measurements made in 278 patients studied 1 year after myocardial infarction. We performed power spectral analyses on continuous 24-hour ECG recordings to quantify total power, ultralow-frequency (ULF) power, very-low-frequency (VLF) power, low-frequency (LF) power, high-frequency (HF) power, and the ratio of LF to HF (LF/HF) power. Time-domain measures also were calculated. All measures of RR variability were significantly and substantially lower in patients with chronic or subacute coronary heart disease than in healthy subjects. The difference from normal values was much greater 2 weeks after myocardial infarction than 1 year after infarction, but the fractional distribution of total power into its four component bands was similar for the three groups. In healthy subjects, ULF power did not change significantly with age; VLF, LF, and HF power decreased significantly as age increased. Patients with chronic coronary heart disease showed little relation between power spectral measures of RR variability and age. Patients with a recent myocardial infarction showed a strong inverse relation between VLF, LF, and HF power and age and a weak inverse relation between ULF power and age. ULF power best separates the healthy group from either of the two coronary heart disease groups. Differences in RR variability between men and women were small and inconsistent among the three groups., Conclusions: All measures of RR variability were significantly and substantially higher in healthy subjects than in patients with chronic or subacute coronary heart disease. The difference between healthy middle-aged persons and those with coronary heart disease was much greater 2 weeks after myocardial infarction than 1 year after infarction, but the fractional distribution of total power into its four component bands was similar for the healthy group and the two coronary heart disease groups. Values of RR variability previously reported to predict death in patients with known chronic coronary heart disease are rarely (approximately 1%) found in healthy middle-aged individuals. Thus, when measures of RR variability are used to screen groups of middle-aged persons to identify individuals who have substantial risk of coronary deaths or arrhythmic events, misclassification of healthy middle-aged persons should be rare.
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- 1995
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8. Exploratory or analytic meta-analysis: should we distinguish between them?
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Anello C and Fleiss JL
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- Bias, Clinical Trials as Topic, Confounding Factors, Epidemiologic, Drug Evaluation, Effect Modifier, Epidemiologic, Humans, Randomized Controlled Trials as Topic, Reproducibility of Results, Data Interpretation, Statistical, Meta-Analysis as Topic
- Abstract
Meta-analysis has been defined as a study and "statistical analysis which combines or integrates the results of several independent studies." Included in this definition are other terms, such as systematic overviews, pooling data, pooling study results, and quantitative literature reviews. Like any study, the questions being asked will influence the design and the method of analysis of the meta-analysis. Since a meta-analysis is a study based on a literature review, it is inherently observational rather than experimental in nature. This idea is supported by the fact that the meta-analyst has limited control over the availability of studies or the information collected and reported in the individual studies. Meta-analysis has been applied to clinical trials and epidemiology. At first glance the potential for bias appears greater in epidemiology than in clinical trials. But this may depend on the question being asked. If randomized clinical trials are limited to improving an estimate of effect or testing a hypothesis in a relatively homogeneous set of effect sizes, the clinical trial will tend to be less prone to bias than a comparable set of epidemiologic studies. In this context, the issue of combinability may dominate the meta-analysis. We refer to this type of meta-analysis as an "analytic" meta-analysis. On the other hand when the goal is to resolve controversy, or pose and answer new questions the main concern of the meta-analysis is to explain the variation in the effect sizes. We refer to this application of a meta-analysis as an "exploratory" meta-analysis. In this second type of meta-analysis the characteristics of the different studies become the focus of the analysis. This leads to the idea that protocols for a meta-analysis should reflect its goals and how the results are to be used. Finally, we will consider whether there is a role of meta-analysis in the field of drug development.
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- 1995
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9. Relation between myocardial infarct location and stroke.
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Bodenheimer MM, Sauer D, Shareef B, Brown MW, Fleiss JL, and Moss AJ
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- Adult, Aged, Cerebrovascular Disorders epidemiology, Diltiazem therapeutic use, Female, Follow-Up Studies, Humans, Incidence, Ischemic Attack, Transient epidemiology, Ischemic Attack, Transient etiology, Male, Middle Aged, Myocardial Infarction drug therapy, Myocardial Infarction epidemiology, Prognosis, Retrospective Studies, Risk Factors, Statistics as Topic methods, Time Factors, Cerebrovascular Disorders etiology, Myocardial Infarction complications
- Abstract
Objectives: We sought to compare the likelihood of stroke in patients with anterior versus nonanterior myocardial infarction., Background: The association between anterior infarction and left ventricular thrombus has led to the assumption that embolization from thrombi is an important cause of stroke in patients with anterior infarction. We hypothesized that if anterior infarction is a cause of left ventricular thrombi, the number of strokes should be disproportionately higher in patients with anterior than nonanterior infarction., Methods: We performed a retrospective analysis of 2,466 patients randomized from day 3 to day 15 after infarction as part of a multicenter placebo-controlled study of diltiazem to prevent cardiac death or myocardial infarction. Any acute focal cerebral disorder resulting in localizing findings characterized as a stroke or transient ischemic attack was considered an event., Results: Of 91 events during a follow-up period of 12 to 52 months, 23 (3.2%) occurred in 724 patients with an anterior and 68 (3.9%) in 1,742 patients with a nonanterior myocardial infarction (relative risk 0.81; 95% confidence interval 0.51 to 1.30). Power analysis revealed that the negativity of the study was not the result of inadequate sample size. Life table analysis showed no difference in cumulative event rate (p = 0.42) according to site of infarction. Cox regression analysis showed that of 10 clinical covariates, only systolic blood pressure was predictive of stroke (p < 0.001). The use of warfarin did not contribute to the model. Finally, the addition of site of infarction (anterior vs. nonanterior) did not contribute significantly to the Cox model., Conclusions: Although there is a significant incidence of stroke after acute myocardial infarction, there is no relation between the occurrence of stroke and site of infarction. These data do not support the presumed causal relation between anterior myocardial infarction, thrombus and stroke.
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- 1994
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10. Predicting mortality after myocardial infarction from the response of RR variability to antiarrhythmic drug therapy.
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Bigger JT Jr, Rolnitzky LM, Steinman RC, and Fleiss JL
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- Encainide therapeutic use, Female, Flecainide therapeutic use, Follow-Up Studies, Humans, Male, Middle Aged, Moricizine therapeutic use, Risk Factors, Anti-Arrhythmia Agents therapeutic use, Cardiac Complexes, Premature drug therapy, Electrocardiography, Ambulatory methods, Heart Conduction System drug effects, Myocardial Infarction mortality, Signal Processing, Computer-Assisted
- Abstract
Objectives: This study was designed to test the hypothesis that antiarrhythmic drugs that decrease RR variability will predict all-cause mortality during follow-up after myocardial infarction., Background: RR variability, a noninvasive indicator of autonomic nervous system activity, predicts death after acute myocardial infarction independently of other risk predictors and changes substantially in response to some drugs. A previous study in patients with chronic heart disease and frequent ventricular premature complexes reported that flecainide decreased vagal modulation of RR intervals but amiodarone did not. The investigators of that study speculated that changes in RR variability during antiarrhythmic drug therapy predict an increased mortality rate during long-term drug treatment. To explore this hypothesis further, we compared the effects of encainide and flecainide, which increase long-term mortality substantially, on RR variability with the effects of placebo and moricizine, which have no significant effect on mortality during long-term treatment of unsustained ventricular arrhythmias after myocardial infarction., Methods: The 24-h power spectral density was computed from the baseline electrocardiographic recordings and drug evaluation tapes, and six frequency domain measures of RR variability were calculated: ultra-low frequency (< 0.0033 Hz), very low frequency (0.0033 to < 0.04 Hz), low frequency (0.04 to < 0.15 Hz) and high frequency power (0.15 to < 0.40 Hz), plus total power (< 0.40 Hz) and the ratio of low to high frequency power. Changes in power spectral measures were related to drug treatment and to mortality., Results: In the placebo group, values for RR interval and RR variability increased because of recovery from the effects of acute myocardial infarction. Contrasting placebo treatment with all three active antiarrhythmic drug treatments taken together showed that of all the measures of RR variability, only NN50, pNN50 and low frequency power changed significantly during drug treatment (Bonferroni adjusted p value < 0.025); these variables all decreased during drug therapy. Contrasting encainide and flecainide with moricizine, we found that the encainide and flecainide groups taken together showed a larger decrease in dLF than moricizine, but the difference was of borderline significance (Bonferroni adjusted p value < 0.08). Survival was significantly worse in the groups treated with encainide and flecainide than in the groups treated with placebo or moricizine (relative risk > 2.0, adjusted p < 0.05). The antiarrhythmic drug-induced change in measures of RR variability was not a significant predictor of all-cause mortality during a year of follow-up after myocardial infarction., Conclusions: Encainide, flecainide and moricizine all caused a decrease in RR variability in patients studied approximately 1 month after acute myocardial infarction. Encainide and flecainide caused a significant increase in mortality rates; placebo and moricizine did not. Baseline measurements of RR variability also predicted all-cause mortality after myocardial infarction. The decrease in RR variability produced by the three antiarrhythmic drugs did not predict mortality during follow-up.
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- 1994
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11. Group psychotherapy during radiotherapy: effects on emotional and physical distress.
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Forester B, Kornfeld DS, Fleiss JL, and Thompson S
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- Adult, Aged, Anorexia diagnosis, Anorexia therapy, Attitude to Health, Fatigue diagnosis, Fatigue therapy, Female, Humans, Male, Middle Aged, Nausea diagnosis, Nausea therapy, Neoplasms psychology, Severity of Illness Index, Sex Factors, Stress, Psychological diagnosis, Stress, Psychological psychology, Vomiting diagnosis, Vomiting therapy, Neoplasms radiotherapy, Psychotherapy, Group, Radiotherapy psychology, Stress, Psychological therapy
- Abstract
Objective: The purpose of this study was to ascertain whether group psychotherapy during radiotherapy for cancer significantly decreases patients' emotional and physical distress., Method: Twenty-four patients receiving radiotherapy were randomly selected for group psychotherapy (six patients per group, 90-minute weekly sessions for 10 weeks). Another 24 patients served as control subjects. Each patient was given the Schedule for Affective Disorders and Schizophrenia (SADS) at the onset of radiotherapy, midway through radiotherapy, at the end of radiotherapy, and 4 and 8 weeks after radiotherapy ended., Results: The combined SADS items for depression, pessimism and hopelessness, somatic preoccupation and worry, social isolation and withdrawal, insomnia, and anxiety and agitation were used as a measure of emotional distress. The combined SADS items for anorexia, nausea and vomiting, and fatigue were used as a measure of physical distress. By 4 weeks after the end of radiotherapy, the patients who received group psychotherapy showed significant decreases in both emotional and physical symptoms, and the decreases were greater than those for the control patients. The subjects who initially seemed unaware of their cancer diagnoses had the lowest baseline levels of emotional and physical distress, but 4 weeks after the end of radiotherapy they had high distress levels., Conclusions: Group therapy may enhance quality of life for cancer patients undergoing radiotherapy by reducing their emotional and physical distress. The degree to which patients acknowledge the diagnosis of malignancy may be a factor in their initial distress level and their response to radiotherapy and group therapy.
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- 1993
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12. The ability of several short-term measures of RR variability to predict mortality after myocardial infarction.
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Bigger JT, Fleiss JL, Rolnitzky LM, and Steinman RC
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- Follow-Up Studies, Humans, Myocardial Infarction diagnosis, Predictive Value of Tests, Proportional Hazards Models, Risk Factors, Survival Analysis, Time Factors, Death, Sudden, Cardiac epidemiology, Electrocardiography, Ambulatory methods, Myocardial Infarction mortality, Signal Processing, Computer-Assisted
- Abstract
Background: We studied 715 patients 2 weeks after myocardial infarction to test the hypothesis that short-term power spectral measures of RR variability (calculated from 2 to 15 minutes of normal RR interval data) will predict all-cause mortality or arrhythmic death., Methods and Results: We performed power spectral analyses on the entire 24-hour RR interval time series. To compare with the 24-hour analyses, we selected short segments of ECG recordings from two time periods for analysis: 8 AM to 4 PM and midnight to 5 AM. The former corresponds to the time interval during which short-term measures of RR variability would most likely be obtained. The latter, during sleep, represent a period of increased vagal tone, which may simulate the conditions that exist when patients have a signal-averaged ECG recorded, ie, lying quietly in the laboratory. Four frequency domain measures were calculated from spectral analysis of heart period data over a 24-hour interval. We computed the 24-hour power spectral density and calculated the power within three frequency bands: (1) 0.0033 to < 0.04 Hz, very low frequency power, (2) 0.04 to < 0.15 Hz, low frequency power, and (3) 0.15 to 0.40 Hz, high frequency power. In addition, we calculated the ratio of low to high frequency power. These measures were calculated for 15-, 10-, 5-, and 2-minute segments during the day and at night. Mean power spectral values from short periods during the day and night were similar to 24-hour values, and the correlations between short segment values and 24-hour values were strong (many correlations were > or = 0.75). Using the optimal cutpoints determined previously for the 24-hour power spectral values, we compared the survival experience of patients with low values for RR variability in short segments of ECG recordings to those with high values. We found that power spectral measures of RR variability were excellent predictors of all-cause, cardiac, and arrhythmic mortality and sudden death. Patients with low values were 2 to 4 times as likely to die over an average follow-up of 31 months as were patients with high values. The power spectral measures of RR variability did not predict arrhythmic or sudden deaths substantially better than all-cause mortality., Conclusions: Power spectral measures of RR variability calculated from short (2 to 15 minutes) ECG recordings are remarkably similar to those calculated over 24 hours. The power spectral measures of RR variability are excellent predictors of all-cause mortality and sudden cardiac death.
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- 1993
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13. Effects of digoxin and enalapril on heart period variability and response to head-up tilt in normal subjects.
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Kaufman ES, Bosner MS, Bigger JT Jr, Stein PK, Kleiger RE, Rolnitzky LM, Steinman RC, and Fleiss JL
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- Adult, Autonomic Nervous System drug effects, Autonomic Nervous System physiology, Circadian Rhythm, Double-Blind Method, Electrocardiography, Ambulatory drug effects, Female, Head, Heart Rate physiology, Humans, Male, Middle Aged, Posture physiology, Digoxin pharmacology, Enalapril pharmacology, Heart Rate drug effects
- Abstract
To test the effects of digitalis and angiotensin-converting enzyme inhibition on the RR interval variability in an electrocardiogram, 20 normal subjects were given digoxin 0.25 mg, enalapril 10 mg, and placebo twice daily in a randomized, double-blind, crossover study. Continuous 24-hour electrocardiographic recordings obtained on day 5 of each treatment were analyzed and several time domain and power spectral measures of heart period variability were calculated. Digoxin markedly increased (up to 51%) indexes of vagal modulation of heart period without changing mean RR interval. Enalapril did not change any measure of heart period variability despite a modest hypotensive effect. To determine the effect of each treatment on the response to orthostatic stress, 10 subjects also underwent 15 minutes of 60 degrees head-up tilt; power spectra were calculated for 15 minutes at 0 degree and at 60 degrees of tilt. Neither active treatment affected the response to head-up tilt.
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- 1993
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14. Predictors of smoking abstinence following a single-session restructuring intervention with self-hypnosis.
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Spiegel D, Frischholz EJ, Fleiss JL, and Spiegel H
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- Adult, Autosuggestion, Female, Follow-Up Studies, Humans, Male, Motivation, Personality, Probability, Smoking psychology, Social Support, Treatment Outcome, Weight Gain, Hypnosis, Smoking Cessation methods, Smoking Prevention
- Abstract
Objective: This study examined the relation of smoking and medical history, social support, and hypnotizability to outcome of a smoking cessation program., Method: A consecutive series of 226 smokers referred for the smoking cessation program were treated with a single-session habit restructuring intervention involving self-hypnosis. They were then followed up for 2 years. Total abstinence from smoking after the intervention was the criterion for successful outcome., Results: Fifty-two percent of the study group achieved complete smoking abstinence 1 week after the intervention; 23% maintained their abstinence for 2 years. Hypnotizability and having been previously able to quit smoking for at least a month significantly predicted the initiation of abstinence. Hypnotizability and living with a significant other person predicted 2-year maintenance of treatment response., Conclusions: These results, while modest, are superior to those of spontaneous efforts to stop smoking. Furthermore, they suggest that it is possible to predict which patients are most likely and which are least likely to respond to such brief smoking cessation interventions.
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- 1993
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15. Interval estimation under two study designs for kappa with binary classifications.
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Hale CA and Fleiss JL
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- Humans, Male, Mathematics, Nuclear Family, Probability, Research Design, HIV Seropositivity epidemiology, Models, Statistical
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Cornfield's test-based method of setting a confidence interval on a parameter associated with a two-by-two contingency table is adapted for use with the measure of agreement kappa. One-sided confidence intervals derived in this way are compared to other intervals proposed for kappa under two study designs. Both designs involve two ratings per subject on a dichotomous scale. In one design the same two raters make all evaluations; in the other, possibly different pairs of raters evaluate different subjects, or the same rater carries out a pair of independent assessments for each subject. It is shown through simulation that lower bounds based on Cornfield's test-based method attain the nominal coverage probability more often than other intervals proposed in the literature.
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- 1993
16. Detection and significance of myocardial ischemia in stable patients after recovery from an acute coronary event. Multicenter Myocardial Ischemia Research Group.
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Moss AJ, Goldstein RE, Hall WJ, Bigger JT Jr, Fleiss JL, Greenberg H, Bodenheimer M, Krone RJ, Marcus FI, and Wackers FJ
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- Adult, Aged, Ambulatory Care, Angina, Unstable therapy, Electrocardiography, Exercise Test, Female, Follow-Up Studies, Hospitalization, Humans, Male, Middle Aged, Myocardial Infarction therapy, Myocardial Ischemia epidemiology, Proportional Hazards Models, Prospective Studies, Thallium Radioisotopes, Treatment Outcome, Angina, Unstable physiopathology, Myocardial Infarction physiopathology, Myocardial Ischemia diagnosis, Myocardial Ischemia etiology
- Abstract
Objective: To determine the clinical significance of silent and symptomatic myocardial ischemia detected by noninvasive testing in stable postcoronary patients., Design: Cohort study with a mean 23-month follow-up., Setting: Ambulatory outpatients after recent hospitalization for an acute coronary event., Patients: Nine hundred thirty-six patients (76% male; mean age, 58 years) who were clinically stable 1 to 6 months after hospitalization for acute myocardial infarction or unstable angina., Interventions: Noninvasive testing involved rest, ambulatory, and exercise electrocardiograms and stress thallium-201 scintigraphy., Main Outcome Measures: Cox regression analysis was used to evaluate the risk (hazard ratio) of first recurrent primary events (cardiac death, nonfatal infarction, or unstable angina) or restricted events (cardiac death or nonfatal infarction) associated with ischemic noninvasive test results., Results: ST segment depression on the rest electrocardiogram was the only noninvasive test variable that identified a significantly increased risk (P = .05) for first recurrent primary events (hazard ratio; 95% confidence limits): rest electrocardiogram ST depression (1.5; 1.00, 2.25); ambulatory electrocardiogram ST depression (0.86; 0.49, 1.51); exercise electrocardiogram ST depression (1.13; 0.82, 1.56); and stress thallium-201 reversible defects (1.3; 0.96, 1.74). Test results were similar for first recurrent restricted events, and in patients with and without angina. Significantly increased risk (P < .05) was noted when exercise-induced ST depression occurred in patients who also had reduced exercise duration (hazard ratio, 3.4) or when reversible thallium-201 defects occurred in patients who also had increased lung uptake (hazard ratio, 2.8). Each high-risk subset made up less than 3% of the population and contained less than 6% of patients with first primary events., Conclusion: Detection of silent or symptomatic myocardial ischemia by non-invasive testing in stable patients 1 to 6 months after an acute coronary event is not useful in identifying patients at increased risk for subsequent coronary events.
- Published
- 1993
17. Factors affecting uniformity in interpretation of planar thallium-201 imaging in a multicenter trial. The Multicenter Study on Silent Myocardial Ischemia (MSSMI) Thallium-201 Investigators.
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Wackers FJ, Bodenheimer M, Fleiss JL, and Brown M
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- Exercise Test, Humans, Image Processing, Computer-Assisted, Observer Variation, Radionuclide Imaging, Reproducibility of Results, Heart diagnostic imaging, Myocardial Ischemia diagnostic imaging, Thallium Radioisotopes
- Abstract
Objectives: This study was designed to assess factors affecting interobserver agreement in interpretation of planar thallium-201 stress imaging in the Multicenter Study on Silent Myocardial Ischemia (MSSMI)., Background: Five hundred fifty-six planar thallium-201 images were interpreted in 24 clinical centers and in a Radionuclide Core Laboratory. The trial's Coordinating and Data Center observed that the participating clinical centers interpreted a significantly greater number of thallium-201 stress studies as abnormal (i.e., myocardial ischemia or scar) than the Core Laboratory, and overall agreement was poor (kappa 0.27)., Methods: Agreement in image interpretation between clinical centers and the Radionuclide Core Laboratory was analyzed by kappa statistics. The reproducibility of the Core Laboratory results on 41 randomly selected test studies was excellent (kappa 0.77). In contrast, the reproducibility of interpretation in the clinical centers on their own studies was at best fair (kappa 0.45). It was hypothesized that the poor agreement and reproducibility in the clinical centers were caused by lack of standardization of image display and lack of objective criteria for image interpretation. To test the effect of standardization, 13 clinical investigators interpreted the same 41 test studies using 1) uniform image display, and 2) uniform quantification of images., Results: The agreement in interpretation between clinical investigators and the Radionuclide Core Laboratory improved modestly with uniformity of image display (kappa 0.57) but improved markedly (kappa 0.66) with quantitative circumferential profile analysis., Conclusions: Lack of standardization in image display and lack of objective criteria for interpretation of thallium-201 images are responsible for suboptimal reproducibility and poor interlaboratory agreement in the interpretation of thallium-201 stress imaging. The adoption of a uniformly accepted method for computer quantification of myocardial perfusion images is crucial to improve agreement in interpretation.
- Published
- 1993
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18. Frequency domain measures of heart period variability to assess risk late after myocardial infarction.
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Bigger JT Jr, Fleiss JL, Rolnitzky LM, and Steinman RC
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- Female, Follow-Up Studies, Fourier Analysis, Humans, Male, Middle Aged, Myocardial Infarction diagnosis, Myocardial Infarction physiopathology, Predictive Value of Tests, Prognosis, Risk Factors, Survival Analysis, Time Factors, Electrocardiography, Ambulatory methods, Myocardial Infarction mortality, Signal Processing, Computer-Assisted
- Abstract
Objectives: To determine whether spectral measures of heart period (RR) variability predict death when measured late after infarction, we studied patients in the Cardiac Arrhythmia Pilot Study (CAPS) who survived for 1 year and had a 24-h electrocardiographic (ECG) recording made after the CAPS drug was washed out., Background: Four components of the heart period power spectrum--ultra low frequency (< 0.0033 Hz), very low frequency (0.0033 to < 0.04 Hz), low frequency (0.04 to < 0.15 Hz) and high frequency power (0.15 to < 0.40 Hz)--plus total power (1.157 x 10(-5) to < 0.40 Hz) and the ratio of low to high frequency power predict mortality when measured < 30 days after myocardial infarction. However, these variables increase to steady state values by 3 months after infarction and the prognostic significance of recovery values is unknown., Methods: The 24-h power spectral density was computed from ECG recordings made 1 year after infarction using fast Fourier transforms and the six measures listed were calculated. The values were dichotomized at cut points that maximized the association with mortality., Results: Each measure of RR variability had a strong and significant univariate association with mortality; the relative risks for these variables ranged from 2.5 to 5.6. After adjustment for age, New York Heart Association functional class, rales in the coronary care unit, left ventricular ejection fraction and ventricular arrhythmias, some measures of heart period variability still had a strong and significant independent association with all-cause mortality., Conclusions: Spectral measures of heart period variability, measured late after infarction, predict death.
- Published
- 1993
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19. The statistical basis of meta-analysis.
- Author
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Fleiss JL
- Subjects
- Clinical Trials as Topic methods, Odds Ratio, Random Allocation, Risk, Meta-Analysis as Topic, Models, Statistical
- Abstract
Two models for study-to-study variation in a meta-analysis are presented, critiqued and illustrated. One, the fixed effects model, takes the studies being analysed as the universe of interest; the other, the random effects model, takes these studies as representing a sample from a larger population of possible studies. With emphasis on clinical trials, this paper illustrates in some detail the application of both models to three summary measures of the effect of an experimental intervention versus a control: the standardized difference for comparing two means, and the relative risk and odds ratio for comparing two proportions.
- Published
- 1993
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- View/download PDF
20. Enrollment in clinical trials: institutional factors affecting enrollment in the cardiac arrhythmia suppression trial (CAST).
- Author
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Shea S, Bigger JT Jr, Campion J, Fleiss JL, Rolnitzky LM, Schron E, Gorkin L, Handshaw K, Kinney MR, and Branyon M
- Subjects
- Arrhythmias, Cardiac prevention & control, Hospitals, Teaching, Humans, Medical Staff, Hospital, Multicenter Studies as Topic, Schools, Medical, Arrhythmias, Cardiac drug therapy, Clinical Trials as Topic, Myocardial Infarction complications
- Abstract
Recruitment and Enrollment Assessment in Clinical Trials (REACT), an NHLBI-sponsored substudy of the Cardiac Arrhythmia Suppression Trial (CAST), was conducted to assess factors associated with enrollment in clinical trials. We report on the relationships of institutional factors at CAST sites to patient enrollment. The proportion of CAST-eligible patients enrolling at each CAST site during the REACT study period was defined as the number of subjects enrolled divided by the sum of (1) the number enrolled plus (2) the number of eligibles who refused plus (3) the number of eligibles whose physicians refused to permit CAST personnel to attempt to enroll them. A questionnaire that included 78 questions regarding factors hypothesized to be associated with enrollment was completed between August 1988 and February 1990 by the nurse coordinators at all 112 CAST sites in the United States and Canada. Sixteen items were unanalyzable, and 37 of the remaining 62 were grouped into seven scales. The remaining items were analyzed individually. Enrollment proportions varied widely across the 112 CAST sites (mean 32.7% SD 22.6). Five variables or scales were included in the final multiple regression model (multiple R2 = .39). The most important of these was the proportion of eligible patients at a site cared for by medical staff other than private attending physicians (multiple R2 for this variable alone, .26). This proportion tended to be high in teaching hospitals. Other variables in this model that were associated with higher enrollment proportions included the number of days per week a nurse coordinator was present at the site, the number of nurse coordinator full-time equivalents at the site, fewer other clinical trials for which the nurse coordinator was responsible, and fewer perceived obstacles to enrollment. These findings indicate that enrollment was more successful at hospitals with higher proportions of eligible subjects cared for by fellows, housestaff, and service attending physicians and at institutions with the committed presence of a nurse-coordinator.
- Published
- 1992
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21. Comparison of 24-hour parasympathetic activity in endurance-trained and untrained young men.
- Author
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Goldsmith RL, Bigger JT Jr, Steinman RC, and Fleiss JL
- Subjects
- Adult, Circadian Rhythm physiology, Electrocardiography, Ambulatory, Humans, Male, Physical Fitness physiology, Sleep physiology, Exercise physiology, Heart physiology, Parasympathetic Nervous System physiology, Physical Endurance physiology
- Abstract
Objectives: This study compares 24-h parasympathetic activity in aerobically trained and untrained healthy young men., Background: Higher values of parasympathetic nervous system activity are associated with a low mortality rate in patients after myocardial infarction, but it remains uncertain what therapeutic interventions can be used to increase parasympathetic activity. Although it is thought that exercise training can increase parasympathetic activity, studies have reported conflicting results, perhaps because this variable was measured for only brief intervals and usually inferred from changes in reflex responses induced by pharmacologic blockade., Methods: Parasympathetic activity was assessed noninvasively from 24-h ECG recordings by calculating high frequency (0.15 to 0.40 Hz) beat to beat heart period variability in eight endurance-trained men (maximal oxygen consumption greater than or equal to 55 ml/kg per min) and eight age-matched (mean = 29 yr) untrained men (maximal oxygen consumption less than or equal to 40 ml/kg per min). The data were analyzed separately for sleeping hours when parasympathetic activity is dominant and also for waking hours., Results: The geometric mean of high frequency power was greater in the trained than in the untrained men during the day (852 vs. 177 ms2, p less than 0.005), during the night (1,874 vs. 427 ms2, p less than 0.005) and over the entire 24 h (1,165 vs. 276 ms2, p less than 0.001)., Conclusions: Parasympathetic activity is substantially greater in trained than in untrained men, and this effect is present during both waking and sleeping hours. These data suggest that exercise training may increase parasympathetic activity over the entire day and may therefore prove to be a useful adjunct or alternative to drug therapy in lessening the derangements of autonomic balance found in many cardiovascular diseases.
- Published
- 1992
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22. General design issues in efficacy, equivalency and superiority trials.
- Author
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Fleiss JL
- Subjects
- Humans, Multicenter Studies as Topic methods, Observer Variation, Patients, Placebos, Random Allocation, Randomized Controlled Trials as Topic standards, Reproducibility of Results, Sampling Studies, Statistics as Topic, Therapeutic Equivalency, Drug Evaluation methods, Periodontal Diseases drug therapy, Randomized Controlled Trials as Topic methods, Research Design
- Abstract
Critical discussion is offered of design issues pertinent to three categories of clinical trials: efficacy trials, in which an experimental intervention is compared to an inert control, and equivalency and superiority trials, in which an experimental intervention is compared to an active control. The issues discussed are sample-size determination and power, problems in designing and analyzing multicenter trials, broad versus concentrated sampling of patients, the need (or not) for a placebo control group in an active control trial, the possible appropriateness of crossing patients over from one regimen to another, various methods of randomization, the intention-to-treat principle in repeated measurements studies, and possible logical conflicts between inferences from superiority trials and inferences from equivalency trials.
- Published
- 1992
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23. Correlations among time and frequency domain measures of heart period variability two weeks after acute myocardial infarction.
- Author
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Bigger JT Jr, Fleiss JL, Steinman RC, Rolnitzky LM, Kleiger RE, and Rottman JN
- Subjects
- Electrocardiography, Ambulatory, Female, Humans, Male, Predictive Value of Tests, Risk Factors, Survival Analysis, Heart Rate, Myocardial Infarction physiopathology
- Abstract
Seven hundred fifteen participants from a multicenter natural history study of acute myocardial infarction were studied (1) to determine the correlations among time and frequency domain measures of heart period variability, (2) to determine the correlations between the measures of heart period variability and previously established post-infarction risk predictors, and (3) to determine the predictive value of time domain measures of heart period variability for death during follow-up after acute myocardial infarction. Twenty-four hour electrocardiographic recordings obtained 11 +/- 3 days after acute myocardial infarction were analyzed and 11 measures of heart period variability were computed. Each of 4 bands in the heart period power spectrum had 1 or 2 corresponding variables in the time domain that correlated with it so strongly (r greater than or equal to 0.90) that the variables were essentially equivalent: ultra low frequency power with SDNN* and SDANN index,* very low frequency power and low-frequency power with SDNN index,* and high-frequency power with r-MSSD* and pNN50.* As expected from theoretical considerations, SDNN and the square root of total power were almost perfectly correlated. Correlations between the time and frequency domain measures of heart period variability and previously identified postinfarction risk predictors, e.g., left ventricular ejection fraction and ventricular arrhythmias, are remarkably weak. Time domain measures of heart period variability, especially those that measure ultra low or low-frequency power, are strongly and independently associated with death during follow-up. * Defined in Table II.
- Published
- 1992
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24. Stability over time of heart period variability in patients with previous myocardial infarction and ventricular arrhythmias. The CAPS and ESVEM investigators.
- Author
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Bigger JT Jr, Fleiss JL, Rolnitzky LM, and Steinman RC
- Subjects
- Adult, Aged, Chi-Square Distribution, Electrocardiography, Ambulatory, Electrophysiology, Female, Humans, Linear Models, Male, Middle Aged, Pilot Projects, Reproducibility of Results, Time Factors, Arrhythmias, Cardiac physiopathology, Heart Rate, Myocardial Infarction physiopathology
- Abstract
To determine the reproducibility of frequency domain measures of heart period variability in patients with previous myocardial infarction, 2 random samples of 40 patients each (1 from the Cardiac Arrhythmia Pilot Study [CAPS] [unsustained ventricular arrhythmias], and 1 from the Electrophysiologic Studies Versus Electrocardiographic Monitoring [ESVEM] [sustained ventricular arrhythmias] trial) were studied. For each patient, two 24-hour continuous electrocardiographic recordings were analyzed, and the average normal RR interval, total power and 4 components of total power were calculated. Group means and standard deviations for each sample were virtually identical for the pairs of 24-hour recordings. Furthermore, measurements for individual patients were stable from day to day, as measured by the intraclass correlation coefficients and the standard errors of measurement. Reproducibility of heart period variability measurements is excellent in patients with previous myocardial infarction and ventricular arrhythmias, and is comparable to the high stability previously found in a small group of normal subjects. The stability of measures of heart period variability facilitates distinguishing real changes due to progression or regression of cardiac disease or to drug effects from apparent changes due to random variation.
- Published
- 1992
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25. The correlation between heart period variability and mean period length.
- Author
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Fleiss JL, Bigger JT Jr, and Rolnitzky LM
- Subjects
- Aged, Autonomic Nervous System physiopathology, Humans, Myocardial Infarction physiopathology, Prognosis, Proportional Hazards Models, Survival Rate, Electrocardiography, Ambulatory statistics & numerical data, Heart Rate physiology, Myocardial Infarction mortality
- Abstract
Heart rate variability and heart period variability are important indicators of the functioning of the autonomic nervous system and are strong predictors of survival after myocardial infarction. The standard deviation of a patient's series of normal heart periods (consecutive normal RR intervals) is positively and, in some populations, strongly correlated with the mean period length. This phenomenon has led some investigators to use the coefficient of variation as their measure of variability, because it correlates less strongly with the mean period length. Using data from a multicentre post-infarction natural history study, we show that the standard deviation of the instantaneous heart rates has, like the coefficient of variation, only a modest correlation with the mean period length. Unlike the coefficient of variation, however, this standard deviation is derivable from established statistical principles. We show further that the coefficient of variation, the standard deviation of heart rates, and the standard deviation of heart periods are approximately equally strong predictors of survival after myocardial infarction.
- Published
- 1992
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26. Frequency domain measures of heart period variability and mortality after myocardial infarction.
- Author
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Bigger JT Jr, Fleiss JL, Steinman RC, Rolnitzky LM, Kleiger RE, and Rottman JN
- Subjects
- Aged, Forecasting, Humans, Multivariate Analysis, Myocardial Infarction physiopathology, Risk Factors, Survival Analysis, Heart Rate, Myocardial Infarction mortality
- Abstract
Background: We studied 715 patients 2 weeks after myocardial infarction to establish the associations between six frequency domain measures of heart period variability (HPV) and mortality during 4 years of follow-up., Methods and Results: Each measure of HPV had a significant and at least moderately strong univariate association with all-cause mortality, cardiac death, and arrhythmic death. Power in the lower-frequency bands--ultra low frequency (ULF) and very low frequency (VLF) power--had stronger associations with all three mortality end points than power in the higher-frequency bands--low frequency (LF) and high frequency (HF) power. The 24-hour total power also had a significant and strong association with all three mortality end points. VLF power was the only variable that was more strongly associated with arrhythmic death than with cardiac death or all-cause mortality. In multivariate Cox regression models using a step-up approach to evaluate the independent associations between frequency domain measures of heart period variability and death of all causes, ULF power was selected first (i.e., was the single component with the strongest association). Adding VLF or LF power to the Cox regression model significantly improved the prediction of outcome. With both ULF and VLF power in the Cox regression model, the addition of the other two components, LF and HF power, singly or together, did not significantly improve the prediction of all-cause mortality. We explored the relation between the heart period variability measures and all-cause mortality, cardiac death, and arrhythmic death before and after adjusting for five previously established postinfarction risk predictors: age, New York Heart Association functional class, rales in the coronary care unit, left ventricular ejection fraction, and ventricular arrhythmias detected in a 24-hour Holter ECG recording., Conclusions: After adjustment for the five risk predictors, the association between mortality and total, ULF, and VLF power remained significant and strong, whereas LF and HF power were only moderately strongly associated with mortality. The tendency for VLF power to be more strongly associated with arrhythmic death than with all-cause or cardiac death was still evident after adjusting for the five covariates. Adding measures of HPV to previously known predictors of risk after myocardial infarction identifies small subgroups with a 2.5-year mortality risk of approximately 50%.
- Published
- 1992
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27. Predicting arrhythmic events after acute myocardial infarction using the signal-averaged electrocardiogram.
- Author
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Steinberg JS, Regan A, Sciacca RR, Bigger JT Jr, and Fleiss JL
- Subjects
- Aged, Arrhythmias, Cardiac etiology, Follow-Up Studies, Heart Ventricles, Humans, Meta-Analysis as Topic, Middle Aged, Myocardial Infarction complications, Predictive Value of Tests, Probability, Prognosis, Prospective Studies, Risk Factors, Tachycardia etiology, Tachycardia physiopathology, Ventricular Function, Left, Arrhythmias, Cardiac physiopathology, Electrocardiography methods, Myocardial Infarction physiopathology, Signal Processing, Computer-Assisted
- Abstract
To determine if the signal-averaged (SA) electrocardiogram (ECG) predicts the occurrence of sustained ventricular arrhythmia and sudden death after acute myocardial infarction, 182 consecutive patients underwent systematic noninvasive testing, including the SAECG. Seventy-one patients (39%) had an abnormal SAECG. The presence of an abnormal SAECG was not related to underlying left ventricular dysfunction or any other clinical or measured variable. There were 16 end points (sustained ventricular arrhythmia or sudden cardiac death) during 14-month follow-up. The SAECG was a significant predictor of these events (p less than 0.02), and an abnormal SAECG conferred a 2.7-fold increase in risk. The risk associated with an abnormal SAECG was independent of both left ventricular function and ventricular arrhythmia on Holter ECG. The SAECG had excellent negative predictive accuracy (95%), but the positive predictive accuracy was low (15%). When the results of the SAECG were combined with the results of the Holter ECG, a group of very high-risk patients was identified; at 18 months, the presence of abnormal SAECG and Holter ECG was associated with a risk of 26% compared with only 4% if both tests were normal. Furthermore, all published studies with a similar design were pooled for meta-analysis. The meta-analysis revealed a sixfold increase in risk, independent of left ventricular function, and an eightfold increase in risk, independent of Holter results when the SAECG was abnormal. The SAECG is a noninvasive test that can rapidly and easily provide potent prognostic information regarding the risk of sustained ventricular arrhythmias for patients after myocardial infarction.
- Published
- 1992
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28. Time course of recovery of heart period variability after myocardial infarction.
- Author
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Bigger JT Jr, Fleiss JL, Rolnitzky LM, Steinman RC, and Schneider WJ
- Subjects
- Aged, Arrhythmias, Cardiac epidemiology, Arrhythmias, Cardiac etiology, Female, Follow-Up Studies, Fourier Analysis, Humans, Incidence, Male, Middle Aged, Myocardial Infarction complications, Myocardial Infarction physiopathology, Pilot Projects, Predictive Value of Tests, Prognosis, Time Factors, Arrhythmias, Cardiac diagnosis, Electrocardiography, Ambulatory standards, Electrophysiology, Heart Rate, Myocardial Infarction mortality
- Abstract
Four components of the heart period power spectrum--ultra low frequency (less than 0.0033 Hz), very low frequency (0.0033 to less than 0.04 Hz), low frequency (0.04 to less than 0.15 Hz) and high frequency power (0.15 to 0.40 Hz)--plus total power (1.157 x 10(-5) to 0.4 Hz for a 24-h electrocardiographic [ECG] recording) all predict mortality after myocardial infarction. To determine the time course and magnitude of recovery for these measures of heart period variability, 68 patients in the Cardiac Arrhythmia Pilot Study (CAPS) placebo group who had 24-h ECG recordings at baseline, 3, 6 and 12 months after myocardial infarction were studied. The 24-h power spectral density was computed with use of fast Fourier transforms and divided into the four components listed previously. The values for the five frequency domain measures of heart period variability in the CAPS patients were similar to those found in 715 patients who participated in the Multicenter Post Infarction Program (MPIP), indicating that the CAPS sample is generally representative of postinfarction patients with respect to these measures. The values for the five measures were one third to one half of those found in 95 normal persons of similar age and gender. There was a substantial increase in all measures of heart period variability between the baseline 24-h ECG recording and the 3-month recording (p less than 0.001). Between 3 and 12 months, the values were quite stable for the group as a whole, as well as for individual patients (intraclass correlation coefficients greater than or equal to 0.66).(ABSTRACT TRUNCATED AT 250 WORDS)
- Published
- 1991
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- View/download PDF
29. Stability over time of variables measuring heart rate variability in normal subjects.
- Author
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Kleiger RE, Bigger JT, Bosner MS, Chung MK, Cook JR, Rolnitzky LM, Steinman R, and Fleiss JL
- Subjects
- Adult, Analysis of Variance, Circadian Rhythm, Electrocardiography, Electrocardiography, Ambulatory, Female, Humans, Male, Middle Aged, Myocardial Contraction physiology, Placebos, Reproducibility of Results, Time Factors, Heart Rate physiology
- Abstract
Both time and frequency domain measures of heart rate (HR) variability have been used to assess autonomic tone in a variety of clinical conditions. Few studies in normal subjects have been performed to determine the stability of HR variability over time, or the correlation between and within time and frequency domain measures of HR variability. Fourteen normal subjects aged 20 to 55 years were studied with baseline and placebo 24-hour ambulatory electrocardiograms performed 3 to 65 days apart to assess the reproducibility of the following time domain measures of cycle length variability: the standard deviation of all normal cycle intervals; mean normal cycle interval; mean day normal cycle interval; night/day difference in mean normal cycle interval; root-mean-square successive cycle interval difference; percentage of differences between adjacent normal cycle length intervals that are greater than 50 ms computed over the entire 24-hour electrocardiographic recording (proportion of adjacent intervals greater than 50 ms); and the frequency domain measures of high (0.15 to 40 Hz), low (0.003 to 0.15) and total (0.003 to 0.40) power. The mean and standard deviations of these measures were virtually identical between placebo and baseline measurements and within the studied time range. Variables strongly dependent on vagal tone (high-frequency, low-frequency and total power, root-mean-square successive difference, and percentage of differences between adjacent normal cycle intervals greater than 50 ms computed over the entire 24-hour electrocardiographic recording) were highly correlated (r greater than 0.8). It is concluded that measures of HR variability are stable over short periods of time.(ABSTRACT TRUNCATED AT 250 WORDS)
- Published
- 1991
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- View/download PDF
30. Reliability of testing measures in Duchenne or Becker muscular dystrophy.
- Author
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Barr AE, Diamond BE, Wade CK, Harashima T, Pecorella WA, Potts CC, Rosenthal H, Fleiss JL, and McMahon DJ
- Subjects
- Child, Humans, Male, Muscle Contraction, Range of Motion, Articular, Reproducibility of Results, Muscular Dystrophies physiopathology
- Abstract
In a multiinstitutional collaborative study, we ascertained the interevaluator and intraevaluator reliability of six physical therapists who performed assessment measures on 36 boys (11.7 +/- 3.9 years) with Duchenne or Becker muscular dystrophy. Upper and lower extremities were evaluated by manual muscle testing for function, range of motion, and strength. The data were analyzed using intraclass correlation coefficients (ICCs). For the interevaluator phase, ICCs were as follows: average muscle strength, .90; range of motion, .76; and upper extremity functional performance, .58. For the intraevaluator phase, corresponding ICCs were .80 to .96; .33 to .97; .34 to 1.00. Our results confirm and extend observations by others that these assessment measures are sufficiently reliable for use in a multiinstitutional collaborative effort. Such results can be used to design clinical trials that have sufficient statistical power to detect changes in the rate of disease progression. Investigators planning clinical trials in a multiinstitutional collaborative setting should first standardize the assessment methods, provide evaluator training, and document reliability.
- Published
- 1991
31. A study of inter- and intra-examiner reliability of pocket depth and attachment level.
- Author
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Fleiss JL, Mann J, Paik M, Goultchin J, and Chilton NW
- Subjects
- Adolescent, Adult, Humans, Observer Variation, Periodontal Diseases diagnosis, Periodontal Diseases pathology, Periodontal Pocket pathology, Periodontics instrumentation, Predictive Value of Tests, Regression Analysis, Epithelial Attachment pathology, Periodontal Diseases epidemiology, Periodontal Pocket diagnosis
- Abstract
Factors affecting inter- and intra-examiner variability for probing pocket depth and periodontal attachment level were studied on a sample of 20 patients, each given six full-month examinations, two by each of 3 examiners. The major determinant of both dimensions of variability was the degree of periodontal destruction, measured as either pocket depth or level of attachment: the greater the degree of destruction, the greater the disagreements within and between examiners. Differences in variability were generally minor between sites on anterior and sites on posterior teeth, between midsites and proximal sites, and between sites on the facial and sites on the lingual surface. When differences were found between the average variances for different kinds of sites, they may have been due to corresponding differences between the average depths, and not to any inherently greater difficulty in measuring one kind of site than another.
- Published
- 1991
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32. Effect of atenolol and diltiazem on heart period variability in normal persons.
- Author
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Cook JR, Bigger JT Jr, Kleiger RE, Fleiss JL, Steinman RC, and Rolnitzky LM
- Subjects
- Adult, Electrocardiography, Ambulatory, Female, Heart innervation, Humans, Male, Myocardial Contraction drug effects, Myocardial Infarction drug therapy, Parasympathetic Nervous System drug effects, Sympathetic Nervous System drug effects, Atenolol pharmacology, Diltiazem pharmacology, Heart drug effects
- Abstract
Several time and frequency domain measures of heart period variability are reduced 1 to 2 weeks after myocardial infarction, and a reduced standard deviation of normal RR intervals over a 24 h period (SDNN) is associated with increased mortality. The predictive accuracy of heart period variability may be reduced by drugs used to treat patients after myocardial infarction. Accordingly, a randomized, three period, placebo-controlled, crossover (Latin square) design was used to determine the effect of atenolol and diltiazem on time and frequency measures of heart period variability calculated from 24 h continuous electrocardiographic recordings during treatment with atenolol, diltiazem and placebo in 18 normal volunteers. During atenolol treatment, the 24 h average normal RR (NN) interval increased 24% (p less than 0.001). The three measures of tonic vagal activity were significantly increased (p less than 0.001) during atenolol treatment: percent of successive normal RR intervals greater than 50 ms = 69%, root mean square successive difference of normal RR intervals = 61% and high frequency power in the heart period power spectrum = 84%. Low frequency power also increased 45% (p less than 0.01), indicating that this variable also is an indicator of tonic vagal activity over 24 h. Diltiazem had no significant effect on the 24 h average NN interval or on any measure of heart period variability. The decreased mortality rate after myocardial infarction associated with beta-adrenergic blocker but not calcium channel blocker therapy may be attributed in part to an increase in vagal tone caused by beta-blockers.
- Published
- 1991
- Full Text
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33. Meta-analysis in epidemiology, with special reference to studies of the association between exposure to environmental tobacco smoke and lung cancer: a critique.
- Author
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Fleiss JL and Gross AJ
- Subjects
- Bias, Humans, Risk Factors, Clinical Trials as Topic methods, Lung Neoplasms etiology, Meta-Analysis as Topic, Tobacco Smoke Pollution adverse effects
- Abstract
Meta-analysis, a set of statistical tools for combining and integrating the results of independent studies of a given scientific issue, can be useful when the stringent conditions under which such integration is valid are met. In this report we point out the difficulties in obtaining sound meta-analyses of either controlled clinical trials or epidemiological studies. We demonstrate that hastily or improperly designed meta-analyses can lead to results that may not be scientifically valid. We note that much care is typically taken when meta-analysis is applied to the results of clinical trials. The Food and Drug Administration, for example, requires strict adherence to the principles we discuss in this paper before it allows a drug's sponsor to use a meta-analysis of separate clinical studies in support of a New Drug Application. Such care does not always carry over to epidemiological studies, as demonstrated by the 1986 report of the National Research Council concerning the purported association between exposure to environmental tobacco smoke and the risk of lung cancer. On the basis of a meta-analysis of 13 studies, 10 of which were retrospective and the remaining 3 prospective in nature, the Council concluded that non-smokers who are exposed to environmental tobacco smoke are at greater risk of acquiring lung cancer than non-smokers not so exposed. In our opinion, this conclusion in unwarranted given the poor quality of the studies on which it is based.
- Published
- 1991
- Full Text
- View/download PDF
34. The variability of spontaneous ventricular arrhythmias in the year after myocardial infarction.
- Author
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Bigger JT Jr and Fleiss JL
- Subjects
- Anti-Arrhythmia Agents adverse effects, Anti-Arrhythmia Agents therapeutic use, Arrhythmias, Cardiac chemically induced, Electrocardiography, Ambulatory, Humans, Pilot Projects, Cardiac Complexes, Premature epidemiology, Myocardial Infarction complications, Tachycardia epidemiology
- Published
- 1991
- Full Text
- View/download PDF
35. Efficient estimation of the heart period power spectrum suitable for physiologic or pharmacologic studies.
- Author
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Rottman JN, Steinman RC, Albrecht P, Bigger JT Jr, Rolnitzky LM, and Fleiss JL
- Subjects
- Algorithms, Heart Function Tests, Humans, Regression Analysis, Time Factors, Electrocardiography, Ambulatory, Heart physiology, Heart Rate physiology, Signal Processing, Computer-Assisted
- Published
- 1990
- Full Text
- View/download PDF
36. Relation between beta-adrenergic blocker use, various correlates of left ventricular function and the chance of developing congestive heart failure. The Multicenter Diltiazem Post-Infarction Research Group.
- Author
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Lichstein E, Hager WD, Gregory JJ, Fleiss JL, Rolnitzky LM, and Bigger JT Jr
- Subjects
- Adult, Aged, Double-Blind Method, Female, Follow-Up Studies, Humans, Male, Middle Aged, Myocardial Infarction mortality, Radiography, Thoracic, Retrospective Studies, Risk, Stroke Volume drug effects, Survival Rate, Adrenergic beta-Antagonists therapeutic use, Heart Failure etiology, Myocardial Infarction drug therapy, Ventricular Function, Left drug effects
- Abstract
This study examined the relations among beta-adrenergic blocker use, various correlates of left ventricular function and the chance of developing congestive heart failure in patients after myocardial infarction. The study was performed with the placebo group of the Multicenter Diltiazem Post-Infarction Trial. Ejection fraction data were available in 1,084 patients; of these, 557 were receiving a beta-blocker and 527 were not. In addition to ejection fraction, other correlates of left ventricular function included the presence or absence of pulmonary rales, chest X-ray film evidence of pulmonary congestion and the presence of an S3 gallop. Beta-blocker use was less frequent in patients with an ejection fraction less than 30%, rales, an S3 gallop and pulmonary congestion on chest X-ray film. Twenty-one percent of patients with an ejection fraction less than 30%, 42% of patients with rales, 28% of patients with an S3 gallop and 28% of patients with pulmonary congestion were receiving beta-blocker therapy. For every correlate of left ventricular function, the chance of developing congestive heart failure was greater in patients with diminished left ventricular function than in those without. For each level of left ventricular function, the chance of developing congestive heart failure requiring treatment was greater in patients not taking a beta-blocker.(ABSTRACT TRUNCATED AT 250 WORDS)
- Published
- 1990
- Full Text
- View/download PDF
37. Autonomic nervous system activity during myocardial ischemia in man estimated by power spectral analysis of heart period variability. The Multicenter Study of Silent Myocardial Ischemia Investigators.
- Author
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Bigger JT Jr, Hoover CA, Steinman RC, Rolnitzky LM, and Fleiss JL
- Subjects
- Aged, Angina, Unstable physiopathology, Electrocardiography, Ambulatory, Female, Humans, Male, Middle Aged, Multicenter Studies as Topic, Myocardial Infarction physiopathology, Autonomic Nervous System physiopathology, Coronary Disease physiopathology, Heart innervation, Heart Rate physiology
- Published
- 1990
- Full Text
- View/download PDF
38. Statistical properties of some clinical measures of gingivitis and periodontitis.
- Author
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Fleiss JL, Turgeon L, Chilton NW, and Listgarten MA
- Subjects
- Analysis of Variance, Epithelial Attachment pathology, Gingivitis therapy, Humans, Periodontal Pocket pathology, Periodontitis therapy, Random Allocation, Statistics as Topic, Dental Health Surveys, Dental Plaque Index, Gingivitis pathology, Periodontal Index, Periodontitis pathology
- Abstract
Various statistical properties of the plaque index, the gingival index, and the whole-mouth averages of pocket depth and attachment level measurements were examined using data from a 4-year randomized trial of 80 patients with a history of treated periodontal disease. Departures from normality were assessed by the median of the standardized distribution, by the coefficients of skewness and kurtosis, and by the Kolmogorov goodness-of-fit test. The relative precisions of probing pocket depth and of attachment level were measured, as were correlations between repeated measurements over time for the four clinical measures. The distribution of the plaque index was far from normal, but the distribution of its logarithm was more nearly normal. The distributions of the other clinical measures were effectively normal to varying degrees of approximation. With only rare exceptions, correlations between repeated measurements on the same clinical variable remained relatively constant no matter how far apart in time the measurements were made, at least up to 4 years. The whole-mouth mean of the attachment level measurements seemed to be relatively more precise than the whole-mouth mean of the pocket depth measurements.
- Published
- 1990
- Full Text
- View/download PDF
39. Effect of diltiazem on cardiac rate and rhythm after myocardial infarction. Multicenter Diltiazem Postinfarction Trial Investigators.
- Author
-
Bigger JT Jr, Coromilas J, Rolnitzky LM, Fleiss JL, and Kleiger RE
- Subjects
- Adult, Aged, Electrocardiography, Ambulatory, Female, Follow-Up Studies, Humans, Male, Middle Aged, Multicenter Studies as Topic, Randomized Controlled Trials as Topic, Arrhythmias, Cardiac prevention & control, Diltiazem therapeutic use, Heart Rate drug effects, Myocardial Contraction drug effects, Myocardial Infarction complications
- Abstract
The a priori hypothesis that diltiazem would reduce the frequency and repetitiveness of ventricular arrhythmias was tested 3 months after myocardial infarction in patients participating in the Multicenter Diltiazem Postinfarction Trial. After 3 months of follow-up, 1,546 of the 2,466 patients enrolled had a 24-hour continuous electrocardiographic recording that contained greater than or equal to 12 hours of analyzable data. They were similar to the patients who survived 3 months but chose not to have a 24-hour electrocardiographic recording (i.e., they were representative of the entire group that survived 3 months). After 3 months of follow-up, there were no significant differences between the diltiazem and placebo groups in the prevalence of atrioventricular block, the frequency of atrial arrhythmias or the frequency or repetitiveness of ventricular arrhythmias. Heart rate was significantly lower (67 +/- 12 vs 71 +/- 12 beats/min) and there was a significantly greater proportion of patients with sinus pauses greater than or equal to 2 seconds in duration in the diltiazem group (6%) than in the placebo group (3%). Comparison with placebo revealed no evidence either for an anti- or proarrhythmic effect of diltiazem. There was no reduction in sudden or arrhythmic death attributable to diltiazem treatment; the fraction of total deaths that were arrhythmic by the Hinkle classification was 41% in the placebo group and 42% in the diltiazem group. It may be that the lack of effect of diltiazem on ventricular arrhythmias is partially responsible for its lack of effect on mortality after myocardial infarction.
- Published
- 1990
- Full Text
- View/download PDF
40. Nonfatal myocardial infarction is, by itself, an inappropriate end point in clinical trials in cardiology.
- Author
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Fleiss JL, Bigger JT Jr, McDermott M, Miller JP, Moon T, Moss AJ, Oakes D, Rolnitzky LM, and Therneau TM
- Subjects
- Double-Blind Method, Humans, Research Design, Clinical Trials as Topic, Myocardial Infarction
- Published
- 1990
- Full Text
- View/download PDF
41. Statistical management of data in clinical research.
- Author
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Fleiss JL and Kingman A
- Subjects
- Analysis of Variance, DMF Index, Double-Blind Method, Humans, Multivariate Analysis, Observer Variation, Research Design, Sampling Studies, Therapeutic Equivalency, Clinical Trials as Topic methods, Clinical Trials as Topic statistics & numerical data, Data Interpretation, Statistical, Dental Caries epidemiology, Randomized Controlled Trials as Topic methods, Randomized Controlled Trials as Topic statistics & numerical data
- Published
- 1990
- Full Text
- View/download PDF
42. [The repression of the lithium pump as an indicator of the response to prophylactic treatment].
- Author
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Fieve RR, Meltzer HL, Dunner DL, and Fleiss JL
- Subjects
- Adjustment Disorders blood, Adult, Female, Humans, Lithium blood, Male, Middle Aged, Reference Values, Adjustment Disorders drug therapy, Lithium therapeutic use
- Published
- 1980
43. Minimum expected cell size requirements for the Mantel-Haenszel one-degree-of-freedom chi-square test and a related rapid procedure.
- Author
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Mantel N and Fleiss JL
- Subjects
- Cell Biology, Epidemiologic Methods, Biometry, Statistics as Topic
- Published
- 1980
- Full Text
- View/download PDF
44. Physical examinations of hospitalized adults.
- Author
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Mudd JW and Fleiss JL
- Subjects
- Age Factors, Anxiety, Attitude, Attitude of Health Personnel, Ethnicity, Female, Hospital Departments, Hospitals, Teaching, Humans, Male, Medicine, Middle Aged, Sex Factors, Socioeconomic Factors, Specialization, Students, Medical, United States, Adult, Hospitalization, Physical Examination standards
- Published
- 1973
- Full Text
- View/download PDF
45. Jackknifing functions of multinomial frequencies, with an application to a measure of concordance.
- Author
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Fleiss JL and Davies M
- Subjects
- Epidemiologic Methods, Statistics as Topic
- Published
- 1982
- Full Text
- View/download PDF
46. Constraints on the validity of computer diagnosis.
- Author
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Spitzer RL, Endicott J, Cohen J, and Fleiss JL
- Subjects
- Computers, Diagnosis, Differential, Humans, Mental Disorders classification, Probability, Psychiatric Status Rating Scales, Terminology as Topic, Diagnosis, Computer-Assisted, Electronic Data Processing, Mental Disorders diagnosis
- Published
- 1974
- Full Text
- View/download PDF
47. Accuracy of the family history method in affective illness. Comparison with direct interviews in family studies.
- Author
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Mendlewicz J, Fleiss JL, Cataldo M, and Rainer JD
- Subjects
- Adult, Affective Symptoms genetics, Aged, Bipolar Disorder diagnosis, Depression diagnosis, Diagnosis, Computer-Assisted, Family, Female, Humans, Male, Memory, Middle Aged, Affective Symptoms diagnosis, Diagnostic Errors, Interview, Psychological, Medical History Taking
- Abstract
We interviewed available spouses and first-degree relatives of 140 bipolar and unipolar probands for current and past psychopathology, and assessed interrater reliability. Diagnoses based on direct interviews of relatives were compared with those based on reports of the probands and of all other interviewed family members. Probands underestimated the prevalence of affective illness and other psychiatric disorders in their relatives, and overestimated the age of onset of illness in their ill relatives. Probands reported more accurately about illness in their spouses and parents than in their siblings and children, but accuracy reached acceptable levels for spouses only. Diagnoses on relatives derived by combining reports of all other interviewed family members, including the proband, were slightly more accurate than those based on the proband's reports alone. Good accuracy was obtained only for reports about spouses.
- Published
- 1975
- Full Text
- View/download PDF
48. Methodological problems arising from the choice of an independent variable in linear regression, with application to an air pollution epidemiological study.
- Author
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Goldstein IF, Fleiss JL, Goldstein M, and Landovitz L
- Subjects
- Environmental Health, Epidemiologic Methods, Humans, Mortality, Sulfur Dioxide, Air Pollution, Models, Theoretical, Regression Analysis
- Abstract
In epidemiological studies using linear regression, it is often necessary for reasons of economy or unavailability of data to use as the independent variable not the variable ideally demanded by the hypothesis under study but some convenient practical approximation to it. We show that if the correlation coefficient between the "practical" and "ideal" variables can be obtained, then a range of uncertainty can be obtained within which the desired regression coefficient of dependent on "ideal" variable may lie. This range can be quite wide, even if the practical and ideal variables are fairly well correlated. These points are illustrated with data on observed regression coefficients from an air pollution epidemiological study, in which pollution measured at one station in a large metropolitan area (containing 40 aerometric stations) was used as the practical approximation to the city-wide average pollution. The uncertainties in the regression coefficients were found to exceed the regression coefficients themselves by large factors. The problem is one that may afflict application of linear regression in general, and suggests caution when selecting independent variables for regression analysis on the basis of convenience, rather than relevance to the hypotheses tested.
- Published
- 1979
- Full Text
- View/download PDF
49. Chromosome examinations after medically administered lysergic acid diethylamide and dextroamphetamine.
- Author
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Jarvik LF, Yen FS, Dahlberg CC, Fleiss JL, Jaffe J, Kato T, and Moralishvili E
- Subjects
- Adult, Cells, Cultured, Chromosome Breakage, Double-Blind Method, Female, Humans, Leukocytes drug effects, Male, Middle Aged, Psychoanalytic Therapy, Chromosomes drug effects, Dextroamphetamine therapeutic use, Lysergic Acid Diethylamide therapeutic use
- Abstract
The results of the present study demonstrate once again that, on the average, the addition of LSD in vitro leads to chromosome damage in excess of that observed in cultures without such added LSD even though nearly all of the in vitro experiments were carried out on blood cultures derived from patients who had already been started on the drug regime in vivo. By contrast, the present data provide no evidence for a measurable detrimental effect of LSD and DA when administered to patients under medical supervision. It is conceivable that an effect might have emerged had we been able to monitor chromosomes separately before and after administration of LSD and before and after administation of DA, but we consider it unlikely that either drug would exert protective action against potentially damaging consequences of the other. It is conceivable also that damaged cells are sequestered to give rise eventually to neoplasia-prone clones. The likelihood of that possibility can be determined only by long-term follow-up studies.
- Published
- 1974
50. Rehospitalization in chronic schizophrenia.
- Author
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Caton CL, Koh SP, Fleiss JL, Barrow S, and Goldstein JM
- Subjects
- Actuarial Analysis, Adolescent, Adult, Aftercare, Chronic Disease, Community Mental Health Services, Female, Humans, Length of Stay, Male, Mathematics, Middle Aged, Models, Theoretical, Patient Compliance, Patient Discharge, Probability, Schizophrenic Psychology, Social Adjustment, Social Support, Stress, Psychological psychology, Patient Readmission, Schizophrenia therapy
- Abstract
This report on rehospitalization in chronic schizophrenia is based on a 1-year study of the postdischarge experiences of 119 chronic schizophrenics in New York City. The life table method of analysis identified the important role of discharge planning, community treatment compliance, and interpersonal stress in the patient's living environment in determining the number of days postdischarge that the patient remained in the community without further inpatient care. A mathematical model to predict days in hospital over the follow-up period, based on three specific components of time in hospital defined in numerical terms (PR, NR, LSR), was devised and tested. The first component, the experience of rehospitalization (PR), was determined by interpersonal stress, social supports, and aftercare treatment compliance. Adequacy of discharge planning, an intervention designed to link the patient to community treatment services, has its greatest impact in identifying number of rehospitalizations for the rehospitalized group (NR). Aftercare treatment compliance has its greatest effect in relation to length of subsequent rehospitalization episodes (LSR). Test of the model revealed that it can predict time in hospital within less than one half of a standard deviation of observed hospital days in approximately 50% of cases.
- Published
- 1985
- Full Text
- View/download PDF
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