Long-Term Exposure to Ambient Air Pollution and Incidence of Cerebrovascular Events:Results from 11 European Cohorts within the ESCAPE Project

BACKGROUND: Few studies have investigated effects of air pollution on the incidence of cerebrovascular events.OBJECTIVES: We assessed the association between long-term exposure to multiple air pollutants and the incidence of stroke in European cohorts.METHODS: Data from 11 cohorts were collected and occurrence of a first stroke was evaluated. Individual air pollution exposures were predicted from land-use regression models developed within the "European Study of Cohorts for Air Pollution Effects" (ESCAPE). The exposures were: PM2.5 (particulate matter [PM] below 2.5 µm in diameter), coarse PM (PM between 2.5 and 10 µm), PM10 (PM below 10 µm), PM2.5 absorbance, nitrogen oxides, and two traffic indicators. Cohort-specific analyses were conducted using Cox proportional hazards models. Random-effects meta-analysis was used for pooled effect estimation.RESULTS: 99,446 subjects were included, 3,086 of whom developed stroke. A 5-μg/m(3) increase in annual PM2.5 exposure was associated with 19% increased risk of incident stroke (hazard ratio [HR] = 1.19, 95% confidence interval [CI]: 0.88, 1.62). Similar findings were obtained for PM10. The results were robust to adjustment for an extensive list of cardiovascular risk factors and noise co-exposure. The association with PM2.5 was apparent among those aged 60+ years (HR = 1.40, 95% CI: 1.05, 1.87), among never-smokers (HR = 1.74, 95% CI: 1.06, 2.88), and among subjects with PM2.5 exposure below 25 μg/m(3) (HR = 1.33, 95% CI: 1.01, 1.77).CONCLUSIONS: We found suggestive evidence of an association between fine particles and incidence of cerebrovascular events in Europe, even at lower concentrations than set by the current air quality limit value.