American Statistical Association New York City Metropolitan Area Chapter Mailman School of Public Health Columbia University Department of Biostatistics Research Talk

The health risks of ambient air pollution exposure have been well quantified in the United States. However, the mechanisms by which exposure is related to health outcomes are not well understood. We can gain insight by studying modifying factors. To this end, we developed and implemented a two-step method to identify modifiers of the relation between particulate air pollution (PM10) levels and daily mortality in 50 cities using data from the National Morbidity and Mortality Air Pollution Study. Analyses identified that the air pollution effect was more pronounced in cities with larger proportions of older adults. Age may have a direct modifying effect, but also it may act as a partial surrogate for health status. To study potential surrogacy, we investigate whether frailty (a measure of health status in older adults) modifies the health effects of air pollution. Low physical activity is a key component in determining frailty using the phenotype introduced in the Cardiovascular Health Study (CHS). In CHS, physical activity was assessed using the long questionnaire at only 3 of the first 10 annual visits. We develop and apply methods to identify and evaluate substitute definitions of low physical activity with the dual goals of streamlining screening and determining low physical activity when the questionnaire information is administratively missing. Results will further elucidate the association of frailty and air pollution with health outcomes and will identify alternative ways of defining frailty.