Association of Ambient PM 1 with Hospital Admission and Recurrence of Stroke: Evidence from 292 Chinese Cities

Background: China suffers from both severe air pollution and stroke burden, but the association of PM1(particles with aerodynamic diameter ≤ 1·0μm) with stroke remains unclear. We estimated the associations of short-term exposure to PM1 with hospital admission and recurrence of stroke in 292 Chinese cities. Methods: Data of 989,591 stroke cases were derived from the Chinese Stroke Center Alliance (CASA) program. Daily air pollution and meteorological data in each selected city were collected to estimate the daily PM1 concentration using a generalized additive model (GAM). A time-stratified case-crossover study design was applied to estimate the associations of short-term exposure to PM1 with hospital admission of stroke. Findings: Each 10μg/m3 increase in PM1(lag06) was associated with a 0·53% (95%CI: 0·39%, 0·67%) increment in hospital admission for all types of stroke, and greater associations were found with ischemic stroke than intracerebral hemorrhage. The associations between PM1 and stroke were statistically significant in Northeast (0·94%, 95 %CI: 0·51%, 1·38 %), North (0·47%, 95%CI: 0·20%, 0·75%), Central (0·57%, 95%CI: 0·30%, 0·85%), and East China (0·63%, 95%CI: 0·27%, 1·00%). The attributable fraction (AF) of hospital admission for stroke caused by PM1 was 2·4% (95%CI: 1·7%, 3·0%). Each 10μg/m3 increase in PM1 was associated with a 1·64% (95%CI: 1·28%, 2·01%) increment in the risk of recurrent stroke. Interpretation: Short-term exposure to PM1 might increase the risk of incidence and recurrence of stroke in China, and the associations varied across different types of stroke and regions. Funding Statement: National Key Research and Development Program of China. Declaration of Interests: We declare no competing interests. Ethics Approval Statement: All participating hospitals in the CSCA were approved to collect data without requiring individual patient informed consent under the common rule or a waiver of authorization and exemption from their institutional review board.