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Hypertension is commonly observed with obstructive sleep apnea (OSA), partly due to dysregulation of sympathetic activity. As OSA is considered male-dominant, potential sex differences in the sympathetic regulation of BP have yet to be explored. Hemodynamic responses to an orthostatic challenge have implications for cardiovascular risk and are sympathetically-modulated. Therefore, we tested the hypothesis that females with OSA have differential BP and HR responses to orthostasis relative to males with OSA. 160 individuals not taking antihypertensive medications completed an overnight polysomnography to identify OSA (apnea-hypopnea index ≥5 events/hr). Orthostatic responses were quantified as the changes (Δ) in BP and HR (assessed via brachial cuff) from rest (10min supine) to 60sec post-standing. Females with (n=17, 42±14yrs, 30.7±6.0kg/m2) and without (n=43, 39±12yrs, 27.6±5.7kg/m2) OSA were compared to males with (n=60, 45±11yrs, 31.4±3.8kg/m2) and without (n=40, 39±13yrs, 27.4±3.1kg/m2) OSA using a one-way ANOVA. There were no between-group differences in age (p>0.05 for post-hoc comparisons) and BMI was lower in both females, and males, without OSA relative to males with OSA (p This work was supported by the National Institutes of Health T32-HL007111 (JMB), HL134808 (NC), HL065176 (PS and VKS), and HL134885 (VKS). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Cardiovascular health disparities are present in several minority racial and ethnic groups including African Americans, who exhibit an increased risk of hypertension compared to non-Hispanic Whites. Somali Americans, a subgroup of African Americans of East African origins, exhibit high rates of diabetes and obesity, conditions often comorbid with impaired blood pressure (BP) regulation. Importantly, it remains unknown whether the disparate cardiovascular risk profile, namely poor nocturnal BP regulation, manifested in African Americans can be applied to Somali Americans. We therefore examined 24-hour BP patterns in Somali Americans compared to White control participants. We hypothesized that Somali Americans would present with heightened nocturnal BP and heart rate (HR). We utilized ambulatory blood pressure monitoring (ABPM) to quantify 24-hour BP patterns in 25 Somali (10 female, 15 male; age: 34 ± 3 years; BMI: 27 ± 1 kg/m2) and 25 White (13 female, 12 male; age: 38 ± 3 years; BMI: 27 ± 1 kg/m2) individuals. Each ABPM recorded a BP reading every 20 minutes throughout the 24-hour period. Subjects were instructed to abstain from caffeine, alcohol, and vigorous exercise during the recording period. From the 24-hour recording, an ambulatory arterial stiffness index (AASI) was calculated as 1 minus the regression slope of systolic (SAP) and diastolic (DAP) arterial pressure. SAP, DAP, and HR obtained between 12:00am and 6:00am were averaged to compute nocturnal means. BP and HR dipping was determined as the percent change between daytime and nocturnal BP and HR. Statistical analysis included independent samples t-tests to determine differences in BP and HR between racial groups (i.e., Somali vs. White). Nocturnal SAP (105 ± 2 vs. 106 ± 3 mmHg, p = 0.364) and DAP (60 ± 1 vs. 58 ± 2 mmHg, p = 0.093) were not different between Somali and White participants. In contrast, nocturnal HR was significantly higher in Somalis compared to Whites (72 ± 2 vs. 64 ± 2 beats/minute, p = 0.009). Similarly, SAP (12 ± 2% vs. 12 ± 1%, p = 0.437) and DAP (18 ± 2% vs. 21 ± 2%, p = 0.127) dipping were comparable between groups, while Somali individuals exhibited blunted HR dipping (11 ± 2% vs. 19 ± 2%, p = 0.008) compared to Whites. AASI (0.32 ± 0.03 vs. 0.24 ± 0.03 a.u., p = 0.031) was higher in Somali compared to White individuals. These findings suggest Somali Americans present with impaired nocturnal cardiovascular regulation and increased arterial stiffness, which may place this racial minority at increased cardiovascular risk. Future work to investigate the mechanistic relationships of cardiovascular dysfunction in Somali Americans is warranted. Research grant from Sleep Number to Mayo Clinic for studies of sleep and cardiovascular risk in Somali Americans, and by NIH R01-HL160619, T32-DK007013, T32-HL007111, and T32-HL105355. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

With rising healthcare costs and the rapid increase in remote physiologic monitoring and care delivery, there is increasing need for economical, accurate and non-invasive continuous measures of blood analytes. Based on radio-frequency identification (RFID), we have developed a novel electromagnetic platform technology (the Bio-RFID platform) to non-invasively penetrate inanimate surfaces, capture data from individual radio frequencies, and convert those data into physiologically meaningful information and insights. Here we describe ground-breaking proof-of-principle studies using Bio-RFID to accurately measure various concentrations of analytes in deionized water. The in vitro Bio-RFID platform consists of an acrylic cuvette in the shape of a 4 inch x 4 inch x 8 inch rectangular prism mounted on the Bio-RFID sensor. This apparatus is in turn mounted on a balance that allows the determination of the mass of the analyte being scanned to within 0.1g. The hardware scans through several thousand radio frequencies and sends the data to proprietary software running on a laptop computer. The software displays a spectral scan known as the Bio-RFID signature of the analyte and computes a similarity metric to compare different signatures.We tested the hypothesis that the Bio-RFID platform is able to precisely and non-invasively measure and identify a variety of analytes in vitro. For this assessment, varying solutions of 1) water in isopropyl alcohol; 2) salt in water; and 3) commercial bleach in water were tested, using a randomized double-blind trial design, as proxies for biochemical solutions in general. The Bio-RFID technology was able to detect concentrations of 2000 parts per million (ppm), with evidence suggesting the ability to detect considerably smaller concentration differences. The novel application of a Bio-RFID electromagnetic platform technology accurately detects, measures, and quantifies specific molecules in liquid. While these findings have in vitro commercial applications, these proof-of-principle studies provide strong support for the application of Bio-RFID technology for non-invasive bio-monitoring of physiologically and medically relevant analytes, such as alcohol and glucose, in the human body. These studies were funded by a grant from Know Labs to Mayo Clinic. PB and JHA are employed by Know Labs. VKS and Mayo Clinic acknowledge a financial interest in Know Labs. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Introduction Although diastolic heart failure (HFpEF) patients frequently have comorbid obstructive sleep apnea (OSA), which has been associated with poor prognosis, the impact of positive airway pressure (PAP) therapy remains unclear. This retrospective study sought to investigate the association between 1 year adherence to PAP therapy and healthcare resource utilization (HCRU) in patients with newly diagnosed OSA and comorbid HFpEF. Methods A national sample of administrative claims data linked to objective PAP therapy usage was used for this analysis. Eligible patients either had two healthcare encounters or one hospitalization with a diastolic heart failure ICD-10 diagnosis code the year prior to being diagnosed with OSA and initiated on PAP therapy. HCRU was measured as a composite outcome of hospitalizations and emergency room (ER) visits. Propensity score matching was used to create well-balanced groups with differing PAP adherence levels to assess the association with 1 year HCRU outcomes. Risk-adjusted models were used to generate the number needed to treat (NNT) that referred to the number of patients that need to become adherent to PAP from non-adherent to avoid 1 visit. Results 4,237 patients with OSA and comorbid HFpEF were included. With propensity score matching, 963 PAP adherent and 963 non-adherent patients remained. After 1 year of PAP therapy, adherent patients had fewer visits than non-adherent patients (1.16 visits per subject vs. 1.75, p < 0.001), driven by a 57% reduction in hospitalizations and a 36% reduction in ER visits for adherent patients. Total HCRU costs were lower in adherent patients than in non-adherent patients ($12,732 vs. $15,610, p< 0.01). Converting 1 patient from non-adherent to adherent would avoid 1.25 visits (either ER visit or hospitalization), with an NNT of 0.8. Conclusion HFpEF patients with OSA that are adherent to PAP therapy for 1 year have fewer hospitalizations and ER visits than patients that are not adherent. More importantly, HCRU costs were lower in adherent patients, highlighting the clinical and economic benefits of treating OSA with PAP therapy in HFpEF patients. Support (if any) Funding Source: ResMed

© Asian Pacific Association for the Study of the Liver 2023, Background: Fatty liver disease in the absence of excessive alcohol consumption is an increasingly common condition with a global prevalence of ~ 25-30% and is also associated with cardiovascular disease (CVD). Since systemic metabolic dysfunction underlies its pathogenesis, the term metabolic (dysfunction)-associated fatty liver disease (MAFLD) has been proposed for this condition. MAFLD is closely intertwined with obesity, type 2 diabetes mellitus and atherogenic dyslipidemia, which are established cardiovascular risk factors. Unlike CVD, which has received attention in the literature on fatty liver disease, the CVD risk associated with MAFLD is often underestimated, especially among Cardiologists. Methods and results: A multidisciplinary panel of fifty-two international experts comprising Hepatologists, Endocrinologists, Diabetologists, Cardiologists and Family Physicians from six continents (Asia, Europe, North America, South America, Africa and Oceania) participated in a formal Delphi survey and developed consensus statements on the association between MAFLD and the risk of CVD. Statements were developed on different aspects of CVD risk, ranging from epidemiology to mechanisms, screening, and management. Conculsions: The expert panel identified important clinical associations between MAFLD and the risk of CVD that could serve to increase awareness of the adverse metabolic and cardiovascular outcomes of MAFLD. Finally, the expert panel also suggests potential areas for future research.

Excessive daytime sleepiness (EDS) is classically viewed as a consequence of insufficient sleep or a symptom of sleep disorders. Epidemiological and clinical evidence have shown that patients reporting EDS in tandem with sleep disorders (e.g., obstructive sleep apnoea) are at greater cardiovascular risk than non-sleepy patients. While this may simply be attributable to EDS being present in patients with a more severe condition, treatment of sleep disorders does not consistently alleviate EDS, indicating potential aetiological differences. Moreover, not all patients with sleep disorders report EDS, and daytime sleepiness may be present even in the absence of any identifiable sleep disorder; thus, EDS could represent an independent pathophysiology. The purpose of this review is twofold: first, to highlight evidence that EDS increases cardiovascular risk in the presence of sleep disorders such as obstructive sleep apnoea, narcolepsy and idiopathic hypersomnia and second, to propose the notion that EDS may also increase cardiovascular risk in the absence of known sleep disorders, as supported by some epidemiological and observational data. We further highlight preliminary evidence suggesting systemic inflammation, which could be attributable to dysfunction of the gut microbiome and adipose tissue, as well as deleterious epigenetic changes, may promote EDS while also increasing cardiovascular risk; however, these pathways may be reciprocal and/or circumstantial. Additionally, gaps within the literature are noted followed by directions for future research.

Introduction Nightshifts represent a substantial proportion of time dedicated to working in the inpatient setting, particularly among ICU staff. Our institution implemented a 24/7 in-person ICU attending model more than a decade ago. With practice growth and more than 200 ICU beds across disciplines, there are now at least 8 ICU attendings in-hospital all night. Yet, little is known about attending staff perceptions and desires about night work, so we began an exploratory analysis. Methods An online survey of 13 multiple-choice, slider scale, and open-ended questions were sent via email to critical care staff physicians of different disciplines within our institution. Results 69 out of 150 physicians completed the survey (46% response rate). Half were between 35 and 45 years old; 29% were age 45 to 55 years old. About half self-identified as a morningness chronotype. Most (84%) work 3- or 4-night shifts consecutively. Most viewed night shift work as having a negative influence on their quality of life (48% “somewhat negative” and 22% “very negative”) and on their health (51% “somewhat negative” and 24% “very negative”). Most would choose to work less nightshifts (37%) or none (29%). During nightshift assignments, about half (53%) self-report an average of 5 hours of sleep per 24-hour period; 18% self-report ≤ 4hours. Only 6% reported 7 or 8 hours of sleep. Mitigating strategies utilized during series of night shifts include use of caffeine (78%), naps (66%) and use of sleeping aids (21%). Outside of the nightshift series, more than half (56%) reported no sleep difficulties while 21% reported onset or maintenance insomnia. Conclusion At our large tertiary hospital employing an in-house nightshift model across multiple ICUs, most staff ICU physicians have a negative perception of night shift work on their quality of life and health. The majority of respondents would choose to work less or no night shifts. How self-reports of limited sleep (average 5 hours) per 24-hour period compare to objectively measured sleep duration in this population remains to be determined in the next phase of this study. Support (if any)

Introduction The prevalence of obstructive sleep apnea (OSA) is high in patients with systolic heart failure (HFrEF) and has been associated with poor prognosis in this patient population. The impact of positive airway pressure (PAP) therapy in patients with OSA and HFrEF remains unclear. This retrospective study sought to investigate the association between 1-year adherence to PAP therapy and healthcare resource utilization (HCRU) in patients with newly diagnosed OSA and comorbid HFrEF. Methods A national sample of administrative claims data linked to objective PAP therapy usage was used for this analysis. Included patients either had two healthcare encounters or one hospitalization with a systolic heart failure ICD-10 diagnosis code the year prior to being diagnosed with OSA and initiated on PAP therapy. HCRU was measured as a composite outcome of hospitalizations, and emergency room (ER) visits. Propensity score matching was used to create well-balanced groups with differing PAP adherence levels to assess the association with 1-year HCRU outcomes. Risk-adjusted models were used to generate the number needed to treat (NNT) that referred to the number of patients that need to become adherent to PAP from non-adherent to avoid 1 visit. Results We identified 3,182 patients with OSA and comorbid HFrEF, and after propensity score matching, 738 patients remained in each group (adherent vs. non-adherent). After 1 year of PAP therapy, adherent patients had fewer visits than non-adherent patients (0.92 vs. 1.15 visits per subject, p = 0.006), which was driven by a 24% reduction in ER visits for adherent patients. Composite hospitalization and ER visit costs were lower in adherent versus non-adherent patients ($3,500 vs. $5,879, p=0.03). The NNT for the entire cohort to avoid one visit was 1.5 patients. Conclusion HFrEF patients with comorbid OSA who were adherent to PAP therapy for 1 year have fewer composite hospitalizations and ER visits than patients that were not adherent. These results highlight the clinical and economic benefits of treating OSA in HFrEF patients. Support (if any) Funding Source: ResMed

Cardiovascular disease (CVD) is a leading cause of death and disability in the United States and worldwide. Untreated obstructive sleep apnea (OSA) is common among older adults with CVD and may increase their risk of hospitalization. However, prior research has been limited by smaller samples of participants undergoing diagnostic sleep testing. Our objective was to estimate the effect of untreated OSA on the risk of hospitalization among older Medicare beneficiaries with CVD age 65+. Using a 5% sample of Medicare administrative claims data from 2006 to 2013, beneficiaries were identified as cases diagnosed with OSA or controls without any sleep-related diagnoses. Then, we restricted only to beneficiaries with a CVD diagnosis by the index date (i.e., OSA diagnosis date or matched date in controls). Next, we assessed the risk of hospitalization, counting only one per beneficiary, during the year before the index date. Because OSA is typically present long before it is diagnosed, the year before OSA diagnosis was assumed to represent a period of untreated OSA. Covariates were balanced between cases and controls using inverse probability of treatment weighting (IPTW). Then using logistic regression, we estimated the risk of hospitalizations the year prior to the index date. Of the 142,893 beneficiaries with CVD, only 19,390 were diagnosed with OSA. In the IPTW model, beneficiaries with untreated OSA were more likely to be hospitalized (odds ratio, 1.82; 95% CI 1.77–1.87). Results suggest screening for OSA among Medicare beneficiaries with CVD may identify older adults at increased risk of hospitalization.

Background The extent of coronary disease affects clinical outcomes and may predict the effectiveness of coronary revascularization with either coronary artery bypass graft (CABG) surgery or percutaneous coronary intervention (PCI). The SYNTAX (Synergy Between Percutaneous Coronary Intervention With Taxus and Cardiac Surgery) score quantifies the extent of coronary disease. Objectives This study sought to determine whether SYNTAX scores predicted outcomes and the effectiveness of coronary revascularization compared with medical therapy in the BARI-2D (Bypass Angioplasty Revascularization Investigation 2 Diabetes) trial. Methods Baseline SYNTAX scores were retrospectively calculated for BARI-2D patients without prior revascularization (N = 1,550) by angiographic laboratory investigators masked to patient characteristics and outcomes. The primary outcome was major cardiovascular events (a composite of death, myocardial infarction, and stroke) over 5 years. Results A mid/high SYNTAX score (≥23) was associated with a higher risk of major cardiovascular events (hazard ratio: 1.36, confidence interval: 1.07 to 1.75, p = 0.01). Patients in the CABG stratum had significantly higher SYNTAX scores: 36% had mid/high SYNTAX scores compared with 13% in the PCI stratum (p Conclusions Among patients with diabetes and stable ischemic heart disease, higher SYNTAX scores predict higher rates of major cardiovascular events and were associated with more favorable outcomes of revascularization compared with medical therapy among patients suitable for CABG. (Bypass Angioplasty Revascularization Investigation in Type 2 Diabetes; NCT00006305)

Introduction: Elevated plasma levels of lipoprotein(a) [Lp(a)] are associated with increased risk for coronary artery disease (CAD), but the strength of the association and whether it is independent of other risk factors remains controversial. Differences in prospective studies may be partially explained by variability in methods used to measure Lp(a). Methods: We utilized two different analytical methods (electrophoretic and immunologic) to measure Lp(a) and determine the predictive value of Llp(a) in assessing angiographic coronary artery disease (CAD) and association with major adverse events in 500 patients. Results: In univariate analyses, median Lp(a) cholesterol and Lp(a) mass were significantly associated with angiographic CAD. In a multivariable model, Lp(a) cholesterol remained a significant correlate of CAD (OR 1.61, 95% CI 1.13-2.31, P = 0.009) while Lp(a) mass was not (OR 1.18, 95% CI 0.95-1.47, P = 0.14). Additionally, on multivariable analysis, the presence of a detectable amount of Lp(a) cholesterol (> or =2.5 mg/dL) was more strongly correlated with CAD than HDL cholesterol < 40 mg/dL, and, along withLp(a) cholesterol, was strongly correlated with major adverse events (OR 2.08 95% CI 1.22-3.56, P = 0.007 and OR 1.22, 95% CI 1.05-1.42, P = 0.012, respectively). Conclusions: Lp(a) cholesterol measured electrophoretically is independently correlated with angiographic CAD and presence of major adverse events, and may be used as an alternative or supplement to Lp(a) mass analysis.

Introduction: Cardiac rehabilitation (CR) is recommended for secondary prevention following a coronary artery disease (CAD) event. The association between CR attendance and long-term major cardiovascular events (MACE)in the community has not been previously reported . Hypothesis: We tested the hypothesis that higher CR participation would be related to a lower risk of MACE,in residents of Olmsted county, Minnesota. Methods: We performed a community-based retrospective longitudinal study on patients referred to CR for CAD events or procedures between the years 2002 and 2012. Follow-up was performed using a record linkage system from the Rochester Epidemiology Project. CR participation was assessed as the number of CR sessions attended, and was analyzed as a continuous variable, as quintiles and also as a binomial variable using 12 sessions as the cutoff. The composite outcome MACE was defined as having an acute coronary syndrome (myocardial infarction (MI) or unstable angina), revascularization (CABG or PCI), ventricular arrhythmias requiring hospitalization, stroke or death from any cause. Multivariate models were adjusted for age and gender and also for factors associated with MACE in the univariate analysis. Results: Our cohort included 2273 patients, 69% males, mean age (SEM) 64 (0.26) years. After a mean follow-up of 6 (0.07) years, 827 patients had an event: MI (73), unstable angina (113), CABG(53), PCI (260), ventricular arrhythmia (13), stroke (72) and death (243). Participation in 12 or more sessions (vs Figure1 . After adjusting for smoking, hypertension, diabetes and history of MI the association remained significant HR 0.85, 95% CI 0.74-0.98, p=0.03. Conclusions: A higher participation in CR was associated with a lower risk of MACE. These results provide additional evidence of important CR health advantages and expand on previous evidence of a dose-response benefit of CR.

Introduction: Estimating body fat content has shown to better predict adiposity-related cardiovascular risk than the commonly used body mass index (BMI). The white-light 3D Body Volume Index Scanner (BVI) is a non-invasive device normally used in the clothing industry to asses body shapes and sizes. We assessed the hypothesis that volume obtained by BVI is comparable to the volume obtained by air displacement plethysmography (BodPod) (COSMED Concord, CA, USA) and thus capable of assessing body fat mass using the bicompartmental principles of body composition. Methods: We compared BVI to BodPod, a validated bicompartmental method to assess body fat percent that uses pressure/volume relationships in isothermal conditions to estimate body volume. Volume is then used to calculate body density (BD) applying the formula density= Body mass/Volume. Body fat mass percentage is then calculated using the Siri formula (4.95/BD – 4.50) х 100. Subjects were members of the Mayo Clinic Dan Abraham Healthy Living Center undergoing a wellness evaluation. Measurements from both devices were obtained the same day. A prediction model for total BodPod volume was developed using linear regression based on 80% of the observations (N=971), as follows: Predicted BodPod Volume (L) = 9.498 + 0.805*(BVI volume, L) - 0.0411*(Age, years) - 3.295*(Male=0, Female=1) + 0.0554*(BVI volume, L)*(Male=0, Female=1) + 0.0282*(Age, years)*(Male=0, Female=1). Predictions for BodPod volume based on the estimated model were then calculated for the remaining 20% (N=243) and compared to the volume measured by the BodPod. Results: Mean (SEM) age was 41.5(0.41) years, 39.4% were men, weight 81.6(0.67) kg, BMI was 27.8 (0.20) kg/m2. Average difference between volume measured by BodPod- predicted volume by BVI was 0.0 L, median: -0.4 L, IQR: -1.8 L to 1.5 L. Average difference between Body fat % measured - predicted was -1%, median: -2.7%, IQR: -13.2 to 9.9, R2 = 0.9845 (Figure 1-A, B). Conclusion: Body fat mass can be estimated using volume measurements obtained by a white- light 3D body scanner (Figure 1-A).

Background: Physical activity (PA) prevents cardiovascular (CV) disease and maintains health. It is unclear which factors predict the adoption or maintenance of PA at a worksite wellness center. Methods: To assess the predictors of increase in PA we conducted a retrospective study on 7237 adults attending a worksite wellness center between September 2008 and October 2011. Upon joining the wellness center, participants completed an electronic or paper survey that assessed for the presence of CV risk factors, height, weight, self-perceived health behaviors and psychosocial factors using eleven validated 0-10 point scale. We included 1927 participants who completed the standard survey at the time of enrollment and at 12 months (+/- 90 days). For logistic regression analysis PA increase at 12 months was defined as an increase of ≥2 points of self-reported PA, on a 0 to 10 point scale, or maintenance of a high level of PA at follow up (FU). Results: Mean (SD) age was 38 (11) yr., BMI was 26.93 (6.06) kg/m 2 and 32% were men. From the study sample, 717 (37%) participants increased their PA level or maintained a high level of PA at FU. When comparing people who increased or maintained a high level of PA with the group without improvement or a decline in PA, there were differences in age and BMI: age [39 (11) vs. 38 (11) yr.; p=0.04] and BMI [27.37 (5.92) vs. 26.68 (5.92) kg/m 2 ; p=0.024]. The Table reports the results of the multivariate logistic regression model. While CV risk factors (tobacco use, hyperglycemia/diabetes mellitus, and high blood cholesterol), perceived stress level and self-perception of being overweight were not significant predictors of increase PA, low muscular strength and flexibility and interactions with close friends were significantly associated with PA. Conclusion: A significant proportion of people, over one-third, enrolled in a wellness center increase their PA level or maintain high levels of PA at 12 months after enrollment. Increasing age and BMI, and a measure of social support; interaction with close friends, and perceived muscular strength and flexibility, predict increase in PA. Presence of CV risk factors do not predict increase in PA. Tailoring programs to address these domains may help younger, less fit, and those with less social support improve their PA level.

Introduction : Obesity is a common risk factor in cardiac rehabilitation (CR), yet many CR patients do not realize significant weight loss, despite engaging in regular exercise training while in CR. Hypothesis : We hypothesized that standard CR would demonstrate favorable body composition (BC) changes even in the absence of weight loss and sought to measure the performance characteristics of weight loss to predict BC changes. Methods : We included consecutive patients enrolled in early outpatient CR who underwent air displacement plethysmography with measurements of height, weight, and waist circumference at initiation and completion of CR. We calculated the accuracy of weight loss to identify significant improvements in BC. Results : Data from 112 patients were available for analysis; mean age 60±12 yr., 76% male, mean body mass index (BMI) 30.2±5.3 kg/m 2 . The indication for CR was myocardial infarction (n=33), percutaneous coronary intervention (n=29), coronary artery bypass or valve surgery (n=45), and heart transplant (n=5). Repeat testing occurred after a median of 81 days and 21 phase II CR sessions. There was no change in BMI (-0.53±1.3 kg/m 2 , p=0.43) and weight (-1.6±4.0 kg, p=0.51). Fat mass showed a borderline significant decrease of 2.9±3.9 kg (p=0.08). However, BC improved significantly as measured by body fat % (-2.5±3.2%, p=0.03) and waist circumference (-4.6±5.2 cm; p=0.01). There was a correlation between weight loss and fat mass loss (r=0.85, p=0.0001, positive predictive value=0.94), and % fat change (r=0.67, p=0.0001, positive predictive value=0.91). See table 1. However, the negative predictive value to detect no fat change for patients who did not lose weight was low (0.49, when assessed by % body fat loss, and 0.57, when assessed by fat mass loss). Among patients who did not lose weight, 29 (51%) had a greater than 1% body fat loss. Conclusions : The diagnostic performance of weight change to predict favorable BC changes is poor and highlights the potential utility of BC measurements in the CR setting. Table. Diagnostic Characteristics of Weight Loss as a Predictor of Improvements in Body Composition Weight Loss (kg) Body Fat % Loss ≤ 1% Fat Mass Loss (kg) > 1kg > 1% ≤ 1kg > 1kg 49 5 51 3 ≤ 1kg or gain 29 28 25 33 Sensitivity 0.63 0.67 Specificity 0.85 0.92 PPV * 0.91 0.94 NPV ** 0.49 0.57 * PPV = Positive Predictive Valve, ** NPV = Negative Predictive Value

There has long been a recognized link between sleep and the autonomic nervous system in both health and disease. This relationship is by far best described in the context of cardiovascular mechanisms, where the autonomic nervous system exerts exquisite control with continuous and rapid adjustments of heart rate (HR), cardiac contractility, vasomotor tone, and vascular capacitance to maintain blood pressure and flow to vital organs. Vasoconstriction in response to sympathetic nervous stimulation modulates distribution of blood flow, particularly in cutaneous, splanchnic, renal, and skeletal muscle vasculature, although less so in cerebral vessels. HR and contractility are influenced by both vagal and sympathetic neural output. Autonomic impulses to the vasculature and heart originate from the vasomotor center in the brain stem, which in turn is modulated by higher nervous regions in the mesencephalon, diencephalon, and portions of the cerebral cortex. Thus, global and regional changes in brain activity have powerful effects on autonomic output, such as during the state change from wakefulness to sleep or, in contrast, those accompanying the increased brain activity characteristic of rapid eye movement (REM) sleep. Although dreaming is thought to occur primarily during REM sleep, the exact function of this sleep stage remains a mystery, but it is clear that physiologic processes that occur during REM sleep have a potentially major impact on cardiopulmonary homeostasis.