Ambient Coarse Particulate Matter and Hospital Admissions for Ischemic Stroke.

Background and Purpose- Evidence on the effects of coarse particulate matter (PM10-2.5) on ischemic stroke is limited and inconsistent. We evaluated the acute effects of PM10-2.5 exposure on hospital admissions for ischemic stroke in China. Methods- We conducted a national time-series analysis of associations between daily PM10-2.5 concentrations and daily hospital admissions for ischemic stroke in China between January 2014 and December 2016. Hospital admissions for ischemic stroke were identified from the database of Urban Employee Basic Medical Insurance, which contains data from 0.28 billion beneficiaries. We applied a city-specific Poisson regression to examine the associations of PM10-2.5 and daily ischemic stroke admissions. We combined the city-specific effect estimates with a random effects meta-analysis, and further evaluated the exposure-response relationship curve and potential effect modifiers. Results- We identified >2 million hospital admissions for ischemic stroke in 172 Chinese cities. A 10 µg/m3 increase in PM10-2.5 concentrations (lag day 0) was associated with a 0.91% (95% CI, 0.73-1.10) increase in hospital admissions for ischemic stroke. The association remained significant after adjusting for PM2.5 (percentage change, 0.96%; 95% CI, 0.75-1.18). The exposure-response relationship was approximately linear, with a moderate response at lower levels (<200 µg/m3) and a steeper response at higher levels. The association was stronger in cities with lower PM10-2.5 concentrations, higher temperatures, or higher relative humidity. Conclusions- This nationwide study provides robust evidence of the short-term association between exposure to PM10-2.5 and increased hospital admissions for ischemic stroke and supports the hypothesis that the association differs by city characteristics.

Association between ambient air pollution and daily hospital admissions for ischemic stroke: A nationwide time-series analysis.

BACKGROUND: Evidence of the short-term effects of ambient air pollution on the risk of ischemic stroke in low- and middle-income countries is limited and inconsistent. We aimed to examine the associations between air pollution and daily hospital admissions for ischemic stroke in China. METHODS AND FINDINGS: We identified hospital admissions for ischemic stroke in 2014-2016 from the national database covering up to 0.28 billion people who received Urban Employee Basic Medical Insurance (UEBMI) in China. We examined the associations between air pollution and daily ischemic stroke admission using a two-stage method. Poisson time-series regression models were firstly fitted to estimate the effects of air pollution in each city. Random-effects meta-analyses were then conducted to combine the estimates. Meta-regression models were applied to explore potential effect modifiers. More than 2 million hospital admissions for ischemic stroke were identified in 172 cities in China. In single-pollutant models, increases of 10 µg/m3 in particulate matter with aerodynamic diameter <2.5 µm (PM2.5), sulfur dioxide (SO2), nitrogen dioxide (NO2), and ozone (O3) and 1 mg/m3 in carbon monoxide (CO) concentrations were associated with 0.34% (95% confidence interval [CI], 0.20%-0.48%), 1.37% (1.05%-1.70%), 1.82% (1.45%-2.19%), 0.01% (-0.14%-0.16%), and 3.24% (2.05%-4.43%) increases in hospital admissions for ischemic stroke on the same day, respectively. SO2 and NO2 associations remained significant in two-pollutant models, but not PM2.5 and CO associations. The effect estimates were greater in cities with lower air pollutant levels and higher air temperatures, as well as in elderly subgroups. The main limitation of the present study was the unavailability of data on individual exposure to ambient air pollution. CONCLUSIONS: As the first national study in China to systematically examine the associations between short-term exposure to ambient air pollution and ischemic stroke, our findings indicate that transient increase in air pollution levels may increase the risk of ischemic stroke, which may have significant public health implications for the reduction of ischemic stroke burden in China.