The effect of short-term exposure to air pollution on the admission of ischemic stroke and its interaction with meteorological factors

Objectives: The aim of this study was to investigate the associations, potential effects, and interactions between short-term exposure to air pollution and the risk of ischemic stroke (IS). Study design: An ecological study. Methods: Daily data on IS incidents, air pollution, and meteorological conditions were collected from 2017 to 2021 in Gannan. A time-stratified case-crossover design, combined with a distributional lag nonlinear model, was employed to analyze the relationship between air pollution exposure and the admission of IS. Additionally, the interaction between air pollutants and meteorological factors was examined using bivariate response surface modeling. The study also conducted stratified analyses based on gender, age, marital status, medical insurance purchase status, and season of admission. Results: In the single lag day structure, extremely low levels of PM2.5 (RR = 1.11, 95 % CI: 1.03-1.20) and PM10 (RR = 1.10, 95 % CI: 1.02-1.20) peaked on lag 3. Conversely, extremely high levels of NO2 (RR = 1.05, 95 % CI: 1.01-1.10), CO (RR = 1.19, 95 % CI: 1.03-1.37), and extremely low levels of O3 (RR = 1.09, 95 % CI: 1.01-1.19) exhibited a greater relative risk on lag 4. In the cumulative lag-day structure, extremely high levels of NO2 exhibited the most significant hazard effect at lag 05 (RR = 1.27, 95 % CI: 1.01-1.52), while extremely low levels of CO at lag 02 (RR = 1.15, 95 % CI: 1.05-1.24) and extremely low levels of O3 at lag 01 (RR = 1.20, 95 % CI: 1.04-1.40) also demonstrated notable associations. In the subgroup stratum, the association between air pollution and IS was found to be more significant in patients who were male, aged <65 years, married, had medical insurance, and were admitted during the cold season. The lowest number of IS hospitalisations occurred under low relative humidity conditions alongside increasing concentrations of CO. Conclusions: Short-term exposure to air pollution was positively associated with an increased risk of IS. This association was influenced by factors such as being male, aged <65 years, married, having medical insurance, and admissions during the cold season. Additionally, an interaction was observed between air pollutants and meteorological factors. These findings carry significant public health implications for the prevention of IS.