Spatial association between ambient fine particulate matter and incident hypertension

Background — Laboratory studies suggest that exposure to fine particulate matter (2.5μm in diameter or less; PM2.5) can trigger a combination of pathophysiological responses that may 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 exposure to ambient PM2.5 is associated with incident hypertension.

Methods and Results — We assembled a cohort of 35,303 non-hypertensive adults from Ontario, Canada who responded to one of four 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=72%, specificity=95%). Estimates of long-term exposure to PM2.5 at participants' postal-code residences were derived from satellite observations. We used Cox proportional hazards models, adjusting for various individual and contextual risk factors including body mass index, smoking, physical activity, and neighbourhood-level unemployment rates. We conducted various sensitivity analyses to assess the robustness of the effect estimate, such as investigating several time windows of exposure and controlling for potential changes in the risk of hypertension over time. Between 1996 and 2010, we identified 8,649 incident cases of hypertension and 2,296 deaths. For every 10µg/m3 increase of PPM2.5, the adjusted hazard ratio (HR10) of incident hypertension was 1.13 (95% confidence interval (CI): 1.05-1.22). Estimated associations were comparable among all sensitivity analyses.

Conclusions — This study supports an association between PM2.5 and incident hypertension.