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.