Associations of particulate matter with stroke mortality: A multicity study in Japan

Objective: Evidence linking short-term exposure to outdoor air pollution with hemorrhagic stroke is inconclusive. Methods: We evaluated the effects of suspended particulate matter (SPM) on cardiovascular disease mortality, focusing on types of stroke, from March 2005 to December 2010, in five selected prefectures in western Japan. A multicity time-series analysis was used, and Asian dust was adjusted in the models. Results: Even after adjusting for Asian dust, the same-day SPM was positively associated with several types of stroke mortality. Following a 10-μg/m³ increase in SPM, rate ratios were 1.014 (90% confidence interval [CI]: 1.002 to 1.026) for stroke, 1.030 (90% CI: 1.004 to 1.056) for intracerebral hemorrhage, and 1.016 (90% CI: 1.003 to 1.030) for ischemic stroke mortality. Conclusions: Short-term exposure to outdoor air pollution may increase the risks of hemorrhagic stroke as well as ischemic stroke mortality.