Epidemiology
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Motorized traffic is an important source of both air pollution and community noise. While there is growing evidence for an adverse effect of ambient air pollution on reproductive health, little is known about the association between traffic noise and pregnancy outcomes. ⋯ Traffic may affect birth weight through exposure to both air pollution and noise.
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Racial residential segregation has been associated with preterm birth. Few studies have examined mediating pathways, in part because, with binary outcomes, indirect effects estimated from multiplicative models generally lack causal interpretation. We develop a method to estimate additive-scale natural direct and indirect effects from logistic regression. We then evaluate whether segregation operates through poor-quality built environment to affect preterm birth. ⋯ Our methodology facilitates the estimation of additive-scale natural effects with binary outcomes. In this study, the total effect of racial segregation on preterm birth was partially mediated by poor-quality built environment.
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Propensity scores are useful for confounding adjustment in the commonly observed setting of many potential confounders, frequent exposure, and rare events. However, with few exposed outcomes to inform covariate selection and many candidate confounders, optimal approaches to construct and implement propensity-score-based confounding adjustment remain unclear. ⋯ The high-dimensional propensity-score algorithm complements expert knowledge for confounding adjustment, but in settings with few exposed outcomes, its performance without investigator-specified covariates is less clear and may be associated with an increased likelihood of bias. In our example, investigator specification of variables combined with high-dimensional propensity-score empirical selection and the use of trimmed propensity-score-stratified analysis seem to improve effect estimation. Plotting the relation of effect estimates to the increasing number of empirical covariates is a useful diagnostic.
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Health behaviors may contribute to socioeconomic inequalities in mortality, although the extent of such contribution remains unclear. We assessed the extent to which smoking, alcohol consumption, and physical inactivity have mediated the association between socioeconomic status (SES) and all-cause mortality in a representative sample of US adults. ⋯ The distribution of health-damaging behaviors may explain a substantial proportion of excess mortality associated with low SES in the United States, suggesting the importance of social inequalities in unhealthy behaviors.
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There is concern about potential effects of radiofrequency fields generated by mobile phones on cancer risk. Most previous studies have found no association between mobile phone use and acoustic neuroma, although information about long-term use is limited. ⋯ The findings do not support the hypothesis that long-term mobile phone use increases the risk of acoustic neuroma. The study suggests that phone use might increase the likelihood that an acoustic neuroma case is detected and that there could be bias in the laterality analyses performed in previous studies.