Acute effects of air pollution on ischaemic stroke onset and deaths: a time-series study in Changzhou, China

Objective To investigate the acute effect of air pollutants on ischaemic stroke (IS) and IS-related death. Setting Five urban districts in Changzhou, China, between 9 January 2015 and 31 December 2016. Participants A total of 32 840 IS cases and 4028 IS deaths were enrolled. Main outcome measures A time-series design, generalised additive model and multivariable regression model were used to examine the percentage change (95% CI) in daily IS counts and deaths with an IQR increase in air pollutant levels for different single or multiple lag days in single-pollutant and two-pollutant models. Results Daily IS counts increased 0.208% (95% CI 0.036% to 0.381%) with an IQR increment in the levels of nitrogen dioxide (NO2). The estimated risk of NO2 was more robust in males and in the cold season. For daily IS counts, the estimated effects of NO2 and sulfur dioxide (SO2) were more significant when adjusted for particulate matter with aerodynamic diameters <2.5 mu m (PM2.5) and PM10. An IQR increment in the concentration of PM10, SO2 and NO2 significantly increased IS deaths with 6 days of cumulative effects (0.268%, 95%CI 0.007% to 1.528%; 0.34%, 0.088% to 0.592%; and 0.263%, 0.004% to 0.522%, respectively). Young individuals (<65 years old) had a higher IS mortality risk for PM2.5, PM10, NO2 and CO. For IS death, the effect estimates of SO2 in the elderly, females and the cold season were more pronounced; statistical significance was also identified for SO2 when adjusted for carbon monoxide (CO). Conclusions This study suggested that short-term exposure to ambient NO2 was associated with increased IS risk. In addition, SO2 was associated with increased IS onset and death.