Association of short-term exposure to air pollution with recurrent ischemic cerebrovascular events in older adults

The acute effects of ambient air pollution on recurrence of ischemic cerebrovascular events (ICEs) remains largely unknown. We therefore conducted a time-stratified case-crossover study of 43,896 patients who were 60 years or older and were admitted to hospital for recurrent ICEs including ischemic stroke and transient ischemic attack in Guangzhou, China during 2016–2019. Based on each patient's home address and pollutant data from its neighboring air quality monitoring stations, we used an inverse distance weighting method to assess exposures to particulate matter with an aerodynamic diameter ≤2.5 μm (PM_2.5), particulate matter with an aerodynamic diameter ≤10 μm (PM₁₀), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), carbon monoxide (CO) and ozone (O₃). Conditional logistic regression models were used to quantify exposure-response associations. During the study period, there were 43,896 case days and 149,131 control days. In single-pollutant models, each 10 μg/m³ increase in exposure to PM₁₀, NO₂ and CO (mean exposure on date of admission and 1 day prior) was significantly associated with a 0.74% (95% confidence interval [CI]: 0.13–1.36%), 2.15% (1.38–2.93%) and 0.14% (0.07–0.21%) increase in odds of hospital admissions for recurrent ICEs, respectively, and no significant departures from linearity were detected. The association for NO₂ exposure remained consistent in 2-pollutant models, while the associations for PM₁₀ and CO disappeared or changed materially with adjustment for other pollutants. Stronger association for NO₂ exposure was observed in cool season than that in warm season. We found that short-term exposure to ambient air pollutants, especially NO₂, was associated with increased risk of hospital admissions for recurrent ICEs in older adults.