Analysis of Air Pollution, Hypertension and Neighborhood Walkability.

Abstract

Introduction: Few studies have explored associations of long-term air pollution exposure with the prevalence and incidence of hypertension, or the joint relationships of neighborhood walkability, individual walking behavior, and social disadvantage. Methods: Air pollution, hypertension, walkability, walking, and covariate data were assessed for >6,000 participants of the Multi-Ethnic Study of Atherosclerosis (MESA) between 2000 and 2007. These participants resided in six communities in the U.S and were aged 45 to 84 and without clinical cardiovascular disease at baseline. Particulate and gaseous air pollution levels (PM2.5, PM10-2.5, NOx) from MESA-generated spatio-temporal models and walkability from the Walk Score Research Services were estimated at participant homes as well as on the census block group level. Census block groups in the six communities having low air pollution and high walk score levels, and the reverse, were classified as “sweet spot” and “sour spot”, respectively. Population characteristics, including percent racial minority, low education level, and below poverty line at the census block group scale were collected from the American Community Survey. Logistic and Cox regressions were used to assess associations between air pollution and prevalent and incident of hypertension. Multinomial logistic regression was used to investigate associations between 1) population characteristics with the sweet/sour spot indicators, and 2) individual walking activity, neighborhood air pollution and walk score. Results: Long-term exposure to ambient PM2.5, NOx, PM10-2.5, and its composite chemicals were not associated with hypertension onset or prevalence at baseline. Geographical distributions of sweet- and sour-spot neighborhoods differed among the six communities. Socially deprived neighborhoods with lower education level populations were less likely to be sweet-spots. Finally, lower ambient PM2.5 levels were associated with more walking for leisure whereas higher walk scores were associated with more walking for transport. Conclusions: Long-term exposures to PM2.5, PM10-2.5 or NOx were not a main contributor to hypertension development in the MESA population, but in some communities, air pollution levels and walkability were associated with personal walking behavior. Socio-economic disadvantage in some communities was linked to higher likelihood of living in a more polluted and less walkable area, potentially contributing to health disparities.