Ambient air pollution and risk for ischemic stroke and transient ischemic attack

Abstract

Objective Data on the association between air pollution and cerebrovascular disease in the United States are limited. The objective of this study was to investigate the association between short‐term exposure to ambient air pollution and risk for ischemic cerebrovascular events in a US community. Methods Daily counts of ischemic strokes/transient ischemic attacks (TIAs) (2001–2005) were obtained from the population‐based Brain Attack Surveillance in Corpus Christi (BASIC) Project. Daily particulate matter less than 2.5μm in diameter (PM_2.5), ozone (O₃), and meteorological data were obtained from Texas Commission on Environmental Quality. To examine the association between PM_2.5 and stroke/TIA risk, we used Poisson regression. Separate models included same‐day PM_2.5, PM_2.5 lagged 1 to 5 days, and an averaged lag effect. All models were adjusted for temperature, day of week, and temporal trends in stroke/TIA. The effects of O₃ were also investigated. Results Median PM_2.5 was 7.0μg/m³ (interquartile range, 4.8–10.0μg/m³). There were borderline significant associations between same‐day (relative risk [RR], 1.03; 95% confidence interval [CI], 0.99–1.07 for an interquartile range increase in PM_2.5) and previous‐day (RR, 1.03; 95% CI, 1.00–1.07) PM_2.5 and stroke/TIA risk. These associations were independent of O₃, which demonstrated similar associations with stroke/TIA risk (same‐day RR, 1.02; 95% CI, 0.97–1.08; previous‐day RR, 1.04; 95% CI, 0.99–1.09). Interpretation We observed associations between recent PM_2.5 and O₃ exposure and ischemic stroke/TIA risk even in this community with relatively low pollutant levels. This study provides data on environmental exposures and stroke risk in the United States, and suggests future research on ambient air pollution and stroke is warranted. Ann Neurol 2008