Background: Recurrent strokes are associated with poor outcomes and mortality. Short-term ambient air pollution may be an important environmental risk factor for stroke recurrence. Although associations between air pollution and stroke risk have been observed, the evidence for short-term effects of air pollution on risk of stroke recurrence is in its infancy. We investigated the association between short-term changes in ambient pollution (particulate matter <2.5μm (PM2.5) and ozone (O3)) and the risk of recurrent ischemic stroke among individuals living in a bi-ethnic community.
Methods: We identified recurrent ischemic stroke cases from the population-based Brain Attack Surveillance in Corpus Christi (BASIC) Project, an ongoing population-based stroke surveillance study in Nueces County, Texas, between 2000 and 2012. Associations between lags of 0 to 3 days PM2.5 and O3 levels and odds of ischemic stroke were assessed using a time-stratified case-crossover design. Conditional logistic regression models were used to calculate odds ratios (ORs) for a 10 unit change in exposure.
Results: There were 317 recurrent ischemic strokes with mean age of 72 years (SD=12). Median levels of PM2.5 and O3 over the study period were 7.7μg/m3 (IQR: 5.6-10.7μg/m3) and 35.2ppb (IQR: 25.0-46.1ppb), respectively. No associations were observed across the different lagged exposures (0 to 3 days) after adjusting for ambient temperature and relative humidity (Figure). Co-adjustment of both pollutants results did not change the results.
Conclusion: No association between PM2.5 and O3 and risk of recurrences was observed. Research on the influence of air pollutants on risk of recurrence is still in its infancy, and more research is needed to understand the relation.