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The distributions for continuous, discrete, and conditional discrete scan statistics are studied. The approach of finite Markov chain imbedding, which has been applied to random permutations as well as to runs and patterns, is extended to compute the distribution of the conditional discrete scan statistic, defined from a sequence of Bernoulli trials. It is shown that the distribution of the continuous scan statistic induced by a Poisson process defined on (0, 1) is a limiting distribution of weighted distributions of conditional discrete scan statistics. Comparisons of rates of convergence as well as numerical comparisons of various bounds and approximations are provided to illustrate the theoretical results. [ABSTRACT FROM AUTHOR]

Background: A zero-inflated continuous outcome is characterized by occurrence of "excess" zeros that more than a single distribution can explain, with the positive observations forming a skewed distribution. Mixture models are employed for regression analysis of zero-inflated data. Moreover, for repeated measures zero-inflated data the clustering structure should also be modeled for an adequate analysis. Methods: Diary of Asthma and Viral Infections Study (DAVIS) was a one year (2004) cohort study conducted at McMaster University to monitor viral infection and respiratory symptoms in children aged 5-11 years with and without asthma. Respiratory symptoms were recorded daily using either an Internet or paper-based diary. Changes in symptoms were assessed by study staff and led to collection of nasal fluid specimens for virological testing. The study objectives included investigating the response of respiratory symptoms to respiratory viral infection in children with and without asthma over a one year period. Due to sparse data daily respiratory symptom scores were aggregated into weekly average scores. More than 70% of the weekly average scores were zero, with the positive scores forming a skewed distribution. We propose a random effects probit/log-skew-normal mixture model to analyze the DAVIS data. The model parameters were estimated using a maximum marginal likelihood approach. A simulation study was conducted to assess the performance of the proposed mixture model if the underlying distribution of the positive response is different from log-skew normal. Results: Viral infection status was highly significant in both probit and log-skew normal model components respectively. The probability of being symptom free was much lower for the week a child was viral positive relative to the week she/he was viral negative. The severity of the symptoms was also greater for the week a child was viral positive. The probability of being symptom free was smaller for asthmatics relative to non-asthmatics throughout the year, whereas there was no difference in the severity of the symptoms between the two groups. Conclusions: A positive association was observed between viral infection status and both the probability of experiencing any respiratory symptoms, and their severity during the year. For DAVIS data the random effects probit - log skew normal model fits significantly better than the random effects probit -log normal model, endorsing our parametric choice for the model. The simulation study indicates that our proposed model seems to be robust to misspecification of the distribution of the positive skewed response. [ABSTRACT FROM AUTHOR]

Objectives: To examine the effect of severe acute respiratory syndrome (SARS) on visits to a community hospital emergency department (ED) during the early stage of the Toronto outbreak in 2003 and for the same period in 2004. We focused on visits for respiratory illness (SARS-like symptoms) and different age groups. Methods: This study is a retrospective review of ED discharge diagnoses obtained from a computerized database, examining the 4-week period starting March 28 for the years 2001-2004. We obtained the discharge diagnosis, age and visit date for each ED patient during the relevant time intervals, then compared visit data from 2003 and 2004 with a baseline derived from the average number of visits during 2001 and 2002. We constructed groupings based on age and respiratory-illness symptoms. Results: During the SARS outbreak in 2003, ED visits declined by 21% (95% confidence interval [Cl], 18%-24%) over the 4-week study period. The greatest reduction was for combined infant and toddler visits (69%; 95% Cl, 58%-79%); these did not recover the following year. However, during the SARS outbreak there was a large increase in the number of visits for respiratory illnesses in adults (61%; 95% Cl, 46%-75%) and in teenagers (132%; 95% Cl, 82%-182%). Conclusions: During the SARS outbreak, total ED visits fell. The relative decline was most notable for infants and toddlers. By contrast, there was an increase in respiratory illness-related visits for adults and teenagers. In 2004, the year following the SARS outbreak, visit patterns shifted toward baseline levels, but ED visits by infants and toddlers remained depressed. [ABSTRACT FROM AUTHOR]

In this article, under very general assumptions on Bernoulli trials, a simple numerical method based on the finite Markov chain imbedding technique is systematically developed to determine (a) the joint distribution of the number of success runs and the number of successes, (b) the conditional distribution of the number of success runs given the number of successes, that is, the exact distribution of the success runs test statistic, (c) the joint distribution of the length of the longest success run and the number of successes, and (d) the conditional distribution of the length of the longest success run given the number of successes, that is, the exact distribution of the longest success run test statistic. The critical regions and powers of these two tests (success runs and longest success run) are derived under the null hypothesis of independence and identical distribution (11d) as well as under the alternative hypothesis of Markov dependence. The application of the success runs test is illustrated using real datasets from a multicenter risk factor study on asthmatics. [ABSTRACT FROM AUTHOR]

The estrogen 17β-estradiol (E) increases the axospinous synaptic density and plasticity in the hippocampal CA1 region of young female rats but fails to do so in aged female rats. This E stimulus on synaptic plasticity is associated with the phosphorylation-dependent activation of Akt kinase. Our previous findings demonstrated that increased estrogen levels subsequently increase phosphorylated Akt (pAkt)-immunoreactivity (-IR) within the dendritic shafts and spines of pyramidal neurons in young female rats. Therefore, because Akt can promote cell survival and growth, we tested the hypothesis that the less plastic synapses of aged female rats would contain less E-stimulated pAkt-IR. Here, young (3-4 months) and aged (22-23 months) female rats were ovariectomized 7 days prior to a 48-h administration of either vehicle or E. The pAkt-IR synaptic distribution was then analyzed using post-embedding electron microscopy. In both young and aged rats, pAkt-IR was found in dendritic spines and terminals, and pAkt-IR was particularly abundant at the post-synaptic density. Quantitative analyses revealed that the percentage of pAkt-labeled synapses was significantly greater in young rats compared to aged rats. Nonetheless, E treatment significantly increased pAkt-IR in pre- and post-synaptic profiles of both young and aged rats, although the stimulus in young rats was notably more widespread. These data support the evidence that hormone-activated signaling associated with cell growth and survival is diminished in the aged brain. However, the observation that E can still increase pAkt-IR in aged synapses presents this signaling component as a candidate target for hormone replacement therapies., (Copyright © 2010. Published by Elsevier B.V.)

Estradiol (E) mediates increased synaptogenesis in the hippocampal CA1 stratum radiatum (sr) and enhances memory in young and some aged female rats, depending on dose and age. Young female rats express more estrogen receptor α (ERα) immunolabeling in CA1sr spine synapse complexes than aged rats and ERα regulation is E sensitive in young but not aged rats. The current study examined whether estrogen receptor β (ERβ) expression in spine synapse complexes may be altered by age or E treatment. Young (3-4 months) and aged (22-23 months) female rats were ovariectomized 7 days prior to implantation of silastic capsules containing either vehicle (cholesterol) or E (10% in cholesterol) for 2 days. ERβ immunoreactivity (ir) in CA1sr was quantitatively analyzed using post-embedding electron microscopy. ERβ-ir was more prominent post-synaptically than pre-synaptically and both age and E treatment affected its synaptic distribution. While age decreased the spine synaptic complex localization of ERβ-ir (i.e., within 60 nm of the pre- and post-synaptic membranes), E treatment increased synaptic ERβ in both young and aged rats. In addition, the E treatment, but not age, increased dendritic shaft labeling. This data demonstrates that like ERα the levels of ERβ-ir decrease in CA1 axospinous synapses with age, however, unlike ERα the levels of ERβ-ir increase in these synapses in both young and aged rats in response to E. This suggests that synaptic ERβ may be a more responsive target to E, particularly in aged females., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Background: Exposure to cats and dogs during childhood has been linked to a lower risk of developing allergies. It remains unclear whether this is due to selective avoidance of pets by families with a history of allergies. The effects of pet ownership in adulthood are unknown., Objectives: We sought to assess the association between cat and dog ownership in childhood and early adulthood and the development of atopy in a population-based birth cohort of 1037 subjects., Methods: Ownership of cats or dogs between birth and age 9 years and between the ages of 18 and 32 years was reported. Skin prick tests to common allergens were performed at 13 and 32 years., Results: There was no evidence that families with a history of atopy avoided owning pets. There were significant cat-by-dog interactions for the development of atopy in both childhood and adulthood. Children who had owned both a cat and a dog were less likely to be atopic at age 13 years. Living with only one of these animals was not protective against atopy. Among those who were not atopic by age 13 years, having both a cat and a dog in adulthood was associated with a lower risk of new atopy by age 32 years. This association was only significant among those with a parental history of atopy. These effects were independent of a range of potential confounding factors., Conclusions: There is a synergistic interaction between cat and dog exposure that is associated with a lower risk of developing atopy in childhood and young adulthood.

Background: The adverse effect of hot weather on health in urban communities is of increasing public health concern, particularly given trends in climate change., Objectives: To demonstrate the potential public health applications of monitoring 911 medical dispatch data for heat-related illness (HRI), using historical data for the summer periods (June 1-August 31) during 2002-2005 in Toronto, Ontario, Canada., Methods: The temporal distribution of the medical dispatch calls was described in relation to a current early warning system and emergency department data from the National Ambulatory Care Reporting System (NACRS). Geospatial methods were used to map the percentage of heat-related calls in each Toronto neighborhood over the study period., Results: The temporal pattern of 911 calls for HRI was similar, and sometimes peaked earlier, than current heat health warning systems (HHWS). The pattern of calls was similar to NACRS HRI visits, with the exception of 2005 where 911 calls peaked earlier. Areas of the city with a relatively higher burden of HRI included low income inner-city neighborhoods, areas with high rates of street-involved individuals, and areas along the waterfront which include summer outdoor recreational activities., Conclusions: Identifying the temporal trends and geospatial patterns of these important environmental health events has the potential to direct targeted public health interventions to mitigate associated morbidity and mortality.

This study aimed to identify personal factors associated with expert and respondent agreement on past occupational exposure. Epidemiologic data was collected from 1995 to 1998 in a community-based, case-control study of prostate cancer. Using longest jobs and excluding agreement on "never" exposure, self-reported and expert estimates of ever/ never exposure, by skin or ingestion, to polycyclic aromatic hydrocarbons were compared. Agreement between respondents and the expert was 53.9 percent (N=1,038), with overreporting being more common than underreporting relative to the expert (31.8 percent versus 14.4 percent). In multiple logistic regression models, white-collar occupational status was significantly associated with overreporting (odds ratio [OR] = 0.142; 95 percent confidence interval [CI]: 0.095-0.211; blue-collar versus white-collar), while age was associated with underreporting (OR=1.077; 95 percent CI: 1.043-1.112; one-year increase). Neither job satisfaction nor risk perception appeared to confound other associations. In future studies, overreporting by white-collar workers might be avoided by providing clearer definitions of exposure, whereas elderly respondents may require aids to enhance exposure recall.