Abstract 9454: Risk of Incident Hypertension in Relation to Long-term Exposure to Ambient Air Pollution in Ontario, Canada

Abstract

Background - Laboratory studies suggest that exposure to fine particulate matter (2.5μm in diameter or less; PM2.5) can trigger a combination of changes in autonomic nervous system activity, systemic inflammation, and blood pressure which may in turn induce the development of hypertension. However, epidemiological evidence relating PM2.5 and hypertension is sparse. We thus conducted a population-based cohort study to determine whether long-term exposure to PM2.5 is associated with incident hypertension. Methods and Results - We assembled a cohort of 46,591 non-hypertensive adults from Ontario, Canada who responded to one of five population-based health surveys between 1996 and 2005 and were followed-up until December 31, 2010. Incident diagnoses of hypertension were ascertained from the Ontario Hypertension Database, a validated registry of persons diagnosed with hypertension in Ontario (sensitivity=73% and specificity=95%). Six-year average concentrations of PM2.5 at the subjects’ residences were derived from satellite observations. We used Cox proportional hazards models, adjusting for various individual and contextual risk factors such as body mass index, smoking, physical activity, and family income. We examined the presence of effect modification for selected comorbidities and sociodemographic characteristics. During the follow-up period from 1996 to 2010, we identified a total of 12,061 incident cases of hypertension. For every 10μg/m3 increase of PM2.5, the adjusted hazard ratio (HR) was 1.16 (95% confidence interval (CI): 1.09-1.24). The strongest evidence for an interaction between PM2.5 and hypertension was for congestive heart failure (CHF): HRs of 2.75 (95% CI: 1.26-5.97) and 1.15 (95% CI: 1.08-1.23) among subjects with and without CHF, respectively (interaction p=0.02). Conclusions - This study suggests that exposure to PM2.5 may be a contributing risk factor to the development of hypertension.