Association of ambient PM1 with hospital admission and recurrence of stroke in China

Background: Particulate matter (PM) pollution is a well-known risk factor of stroke. However, little is known about the association between PM1 (aerodynamic diameter & LE; 1.0 mu m) and stroke. We estimated the associations of short-term exposure to PM1 with hospital admission and recurrence of stoke in China.Methods: Stroke data were derived from the Chinese Stroke Center Alliance (CASA) program conducted in 1458 hospitals in 292 Chinese cities from 2015 to 2019. Daily air pollution and meteorological data were collected in the cities where studied hospitals were located. Daily PM1 concentration was estimated by a generalized additive model (GAM) using PM2.5 and meteorological variables. A time-stratified case-crossover design was applied to estimate the associations of short-term exposure to PM1 with hospital admission of stroke. A GAM model was used to estimate the association between average PM1 exposure during hospitalization and the recurrence of stroke.Results: A total of 989,591 stroke cases were included in the study. Each 10 mu g/m3 increase in PM1 (lag06-day) was associated with a 0.53% (95%CI, 0.39%, 0.67%) increment in hospital admission for stroke. The adverse effects of PM1 on ischemic stroke was stronger than on intracerebral hemorrhage. We found the associations were 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%, 0.99%). Of all stroke cases, 62,988 (6.4%) had recurrent stoke attack during their hospitalization. Each 10 mu g/m(3) increase in PM1 was associated with a 1.64% (95%CI, 1.28%, 2.01%) increment in recurrence of stroke during hospitalization.Conclusions: Short-term exposure to PM1 may increase the risk of incidence and recurrence of stroke in China, and the effects varied across different types of stroke and regions. Geographically targeted strategies and measures are needed to control air pollution for reducing the burden of stroke from PM1.