Ambient fine particulate matter air pollution and leisure-time physical inactivity among US adults

Objectives: There is mounting evidence documenting the adverse health effects of short- and long-term exposure to ambient fine particulate matter (PM_2.5) air pollution, but population-based evidence linking PM_2.5 and health behaviour remains lacking. This study examined the relationship between ambient PM_2.5 air pollution and leisure-time physical inactivity among US adults 18 years of age and above. Study design: Retrospective data analysis. Methods: Participant-level data (n = 2,381,292) from the Behavioral Risk Factor Surveillance System 2003-2011 surveys were linked with Wide-ranging Online Data for Epidemiologic Research air quality data by participants' residential county and interview month/year. Multilevel logistic regressions were performed to examine the effect of ambient PM_2.5 air pollution on participants' leisure-time physical inactivity, accounting for various individual and county-level characteristics. Regressions were estimated on the overall sample and subsamples stratified by sex, age cohort, race/ethnicity and body weight status. Results: One unit (μg/m³) increase in county monthly average PM_2.5 concentration was found to be associated with an increase in the odds of physical inactivity by 0.46% (95% confidence interval = 0.34%-0.59%). The effect was similar between the sexes but to some extent (although not always statistically significant) larger for younger adults, Hispanics, and overweight/obese individuals compared with older adults, non-Hispanic whites or African Americans, and normal weight individuals, respectively. Conclusions: Ambient PM_2.5 air pollution is found to be associated with a modest but measurable increase in individuals' leisure-time physical inactivity, and the relationship tends to differ across population subgroups.