Association between ozone exposure and onset of stroke in Allegheny County, Pennsylvania, USA, 1994-2000.

Background: Epidemiological studies have shown adverse short-term effects of air pollution on health including cardiovascular morbidity and mortality. However, air pollution-related stroke has received less attention.

Methods: In this study, we performed a time-stratified case-crossover analysis to evaluate the relationships between stroke hospital admissions and O3, among patients aged 65 years and older in Allegheny County, Pa., USA, between 1994 and 2000. We also examined whether the effects of air pollutants differed across strata defined by patient demographic characteristics and ambient temperature.

Results: Exposures to O3 on the current day increase the risk of total stroke hospitalization by 1.9% (95% CI: 0.01-3.8) per interquartile range increase in concentration. Furthermore, the results suggest that males were more sensitive to adverse health effects of O3 on stroke hospitalization than females.

Conclusion: These results suggest that O3 has an adverse effect on stroke hospitalization. Specific patient subgroups, such as males, may be at increased risk.