Particulate air pollution and survival after stroke in older adults: A retrospective cohort study in Korea

Although many studies have evaluated the effects of ambient particulate matter with diameters of less than 2.5 μm (PM_2.5) on stroke mortality in the general population, little is known about the mortality effects of PM_2.5 in post-stroke populations. Therefore, a retrospective cohort was constructed using information from the health insurance database to evaluate whether exposure to PM_2.5 is associated with increased mortality in aged stroke survivors residing in seven Korean metropolitan cities. A total of 45,513 older adults (≥65 years) who visited emergency rooms due to stroke and who were discharged alive between 2008 and 2016 were followed up. By using district-level modeled PM_2.5 concentrations and a time-varying Cox proportional hazard model, associations between 1-month and 2-month moving average PM_2.5 exposures and mortality in stroke survivors were evaluated. The annual average concentration of PM_2.5 was 27.9 μg/m³ in the seven metropolitan cities, and 14,880 subjects died during the follow-up period. A 10 μg/m³ increase in the 1-month and 2-month moving average PM_2.5 exposures was associated with mortality hazard ratios of 1.07 (95% confidence interval: 1.05, 1.09) and 1.06 (95% confidence interval: 1.03, 1.08), respectively. The effects of PM_2.5 were similar across types of stroke (ischemic and hemorrhagic), age groups (65-74, 75-84, and ≥85), and income groups (low and high) but were greater in women than in men. This study highlights the adverse health effects of ambient PM_2.5 in post-stroke populations. Active avoidance behaviors against PM_2.5 are recommended for aged stroke survivors.