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

Abstract

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 µm (PM_2.5) 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 PM_2.5, 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.

Keywords: cardiac epidemiology; ischaemic heart disease; public health.

Figure 1

The percentage change in daily IS counts and daily IS deaths with an IQR increase in air pollutant levels on different lag days in single-pollutant models in Changzhou, 2015–2016. The data are expressed as the mean with a 95% CI. CO, carbon monoxide; IS, ischaemic stroke; NO₂, nitrogen dioxide; PM_2.5, particulate matter <2.5 µm in diameter; PM₁₀, particulate matter <10 µm in diameter; SO₂, sulfur dioxide.

Figure 2

The concentration–response relationships of daily IS counts, daily IS deaths with air pollutants on different lag days (lag 0–5 for daily IS counts and lag 5 for daily IS deaths) in single-pollutant models in Changzhou, 2015–2016. IS, ischaemic stroke; NO ₂, nitrogen dioxide; PM₁₀, particulate matter <10 µm in diameter; RR, risk ratio; SO₂, sulfur dioxide.