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 (NO 2 ). The estimated risk of NO 2 was more robust in males and in the cold season. For daily IS counts, the estimated effects of NO 2 and sulfur dioxide (SO 2 ) were more significant when adjusted for particulate matter with aerodynamic diameters <2.5 µm (PM 2.5 ) and PM 10 . An IQR increment in the concentration of PM 10 , SO 2 and NO 2 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 PM 2.5 , PM 10 , NO 2 and CO. For IS death, the effect estimates of SO 2 in the elderly, females and the cold season were more pronounced; statistical significance was also identified for SO 2 when adjusted for carbon monoxide (CO). Conclusions This study suggested that short-term exposure to ambient NO 2 was associated with increased IS risk. In addition, SO 2 was associated with increased IS onset and death.