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BACKGROUND Measures to assess neighborhood environments are needed to better understand the salient features that may enhance outdoor physical activities, such as walking and bicycling for transport or leisure. The purpose of this study was to derive constructs to describe neighborhoods using both primary (neighborhood audit) and secondary (geographic(More)
The built environment may be responsible for making nonmotorized transportation inconvenient, resulting in declines in physical activity. However, few studies have assessed both the perceived and objectively measured environment in association with physical activity outcomes. The purpose of this study was to describe the associations between perceptions and(More)
In studies of complex health conditions, mixtures of discrete outcomes (event time, count, binary, ordered categorical) are commonly collected. For example, studies of skin tumorigenesis record latency time prior to the first tumor, increases in the number of tumors at each week, and the occurrence of internal tumors at the time of death. Motivated by this(More)
BACKGROUND Realizing the importance of regular physical activity, particularly in the prevention of chronic diseases and unhealthy weight gain, it is important to study how physical activity changes during and after pregnancy using prospective study designs. The aim of this study was to describe the mode, duration, intensity, and changes in physical(More)
BACKGROUND Polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT) are persistent, bioaccumulative, and toxic pollutants that were broadly used in the United States until the 1970s. Common exposure to PCBs, DDT, and dichlorodiphenyldichloroethylene (DDE), the most stable metabolite of DDT, may influence children's neurodevelopment, but(More)
BACKGROUND Epidemiologic literature suggests that exposure to air pollutants is associated with fetal development. OBJECTIVES We investigated maternal exposures to air pollutants during weeks 2-8 of pregnancy and their associations with congenital heart defects. METHODS Mothers from the National Birth Defects Prevention Study, a nine-state case-control(More)
OBJECTIVE The objective of the study was to determine the association between child BMI at age 3 years and maternal glucose concentration among women without pre-existing diabetes or a gestational diabetes mellitus (GDM) diagnosis. RESEARCH DESIGN AND METHODS Data are from the Pregnancy Infection and Nutrition and Postpartum studies and include 263(More)
Preterm delivery can lead to serious infant health outcomes, including death and lifelong disability. Small increases in preterm delivery risk in relation to spatial gradients of air pollution have been reported, but previous studies may have controlled inadequately for individual factors. Using a time-series analysis, which eliminates potential confounding(More)
In epidemiologic studies, there is often interest in assessing the relationship between polymorphisms in functionally-related genes and a health outcome. For each candidate gene, single nucleotide polymorphism (SNP) data are collected at a number of locations, resulting in a large number of possible genotypes. Because instabilities can result in analyses(More)
Exposure to toxic metals during the prenatal period carries the potential for adverse developmental effects to the fetus, yet such exposure remains largely unmonitored in the United States. The aim of this study was to assess maternal exposure to four toxic metals (arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb)) in a cohort of pregnant women in(More)