Stroke mortality associated with living near main roads in England and Wales - A geographical study

Background and Purpose - Air pollution is associated with stroke, and road traffic is a major source of outdoor air pollution. Using proximity to roads as a proxy for exposure to road traffic pollution, we examined the hypothesis that living near main roads increases the risk of stroke mortality. Methods - We used a small- area ecological study design based on 113 465 census enumeration districts in England and Wales. Stroke mortality ( International Classification of Disease, 9th revision, codes 430 through 438) in England and Wales from 1990 to 1992 for people greater than or equal to 45 years of age was examined through the use of 1991 population denominators. Exposure was calculated as distance from each enumeration district population centroid to the nearest main road. We adjusted for age, sex, socioeconomic deprivation ( using Carstairs index), regional variation, urbanization, and metropolitan area using Poisson regression. Results - The analysis was based on 189 966 stroke deaths and a population of 19 083 979. After adjustment for potential confounders, stroke mortality was 7% ( 95% confidence interval [ CI], 4 to 9) higher in men living within 200 m of a main road compared with men living greater than or equal to 1000 m away. The corresponding increase in risk for women was 4% ( 95% CI, 2 to 6) and the risk for men and women combined was 5% ( 95% CI, 4 to 7). These raised risks diminished with increasing distance from main roads. Conclusions - Living near main roads is associated with excess risk of mortality from stroke, and if causality were assumed, approximate to 990 stroke deaths per year would have been attributable to road traffic pollution.