Cardiovascular Mortality Reductions Related to Improved Air Quality Vary by Socioeconomic Status: A Moderated Mediation Analysis

摘要

Background: Chronic air pollution exposure is a risk factor for cardiovascular disease (CVD) and recent work suggests that CVD mortality reduction over time is partially attributed to improved air quality. We assessed the extent that mortality reduction via PM2.5 change varies by county characteristics and focused on socioeconomic (SES) variables (income, poverty, and unemployment), initial air pollution and sources, employment by sector, and built environment. Methods: Data for 2,132 US counties between 1990 and 2010 included annual age standardized mortality rates from the US National Center for Health Statistics, annual average PM2.5 concentrations from the US Environmental Protection Agency's Community Multiscale Air Quality (CMAQ) modeling framework, baseline SES, and county urbanization level (metropolitan, metro; non-metropolitan, non-metro). A moderated mediation analysis using weighted linear models measured how the indirect effect on CVD mortality via PM2.5 is moderated by county SES status and urbanization level. Average mediation at different levels of SES were estimated from bootstrap replications. Results: In a preliminary analysis, SES moderated the PM2.5-mediated cardiovascular trend differently in metro and non-metro counties. Trends in annual PM2.5 reduction and the health benefit (mortality reduction) per 1 microgram PM2.5 by SES status were similar between metro and non-metro counties. PM2.5 reductions were greatest in counties with higher income, lower poverty, and lower unemployment, while the largest health benefits were observed in counties with lower SES status. In metro counties, PM2.5 mediation was moderated by county poverty level, with increased mediation in counties with greater poverty. In non-metro counties, mediation via PM2.5 was consistent for all poverty levels. Conclusions: We identified that PM mediated health benefits were greatest in metropolitan counties with greater SES status. This abstract does not reflect EPA policy.