Short-term effect of PM 1 on hospital admission for ischemic stroke: A multi-city case-crossover study in China.

This study aims to examine the association between short-term exposures to PM1, PM2.5 and PM10 (particulate matter with aerodynamic diameters ≤1 μm, ≤2.5 μm and ≤10 μm, respectively) and hospital admission for ischemic stroke in China. Daily counts of hospital admission for ischemic stroke were collected in 5 hospitals in China during November 2013 to October 2015. Daily concentrations of PM1, PM2.5 and PM10 were collected in 5 cities where the hospitals were located. A time-stratified case-crossover design was used to examine the hospital-specific PM-ischemic stroke association after controlling for potential confounders. Then the effect estimates were pooled using a random-effect meta-analysis. A total of 68,122 hospital admissions for ischemic stroke were identified from 5 hospitals during the study period. The pooled results showed that exposures to PM1, PM2.5 and PM10 were significantly associated with increased hospital admission for ischemic stroke on the current day and previous 1 day. The RRs (relative risk associated with per 10 μg/m3 increase in each pollutant) and 95%CIs (confidence intervals) for the cumulative effects of PM1, PM2.5 and PM10 on ischemic stroke during lag 0–1 days were 1.014 (1.005, 1.0023), 1.007 (1.000, 1.014) and 1.005 (1.001, 1.009), respectively. In total, 3.5%, 3.6% and 4.1% of hospital admissions for ischemic stroke could be attributable to PM1, PM2.5 and PM10, respectively. Exposures to ambient PM1, PM2.5 and PM10 pollution showed acute adverse effects on hospital admission for ischemic stroke. The health effects of PM1 should be considered by policy-makers.