Association of short-term exposure to air pollution with ischemic stroke hospitalization among hypertensive patients in Beijing

  Objective  To analyze the association of short-term exposure to air pollution with ischemic stroke (IS)-related hospitalization among hypertensive patients in Beijing and to provide evidences for protecting the patients from air pollution and revising air quality standards.

  Methods  The information on 315 499 hospitalized IS patients with hypertension during 2014 – 2018 were extracted from the medical record database of Beijing Municipal Health Commission Information Center. The data of the same period on daily concentration of particulate matter ≤ 2.5 μm / ≤ 10 μm in aerodynamic diameter (PM_2.5/PM₁₀), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), ozone (O₃) and carbon monoxide (CO) were collected from Beijing Environmental Protection Testing Center and daily meteorological data were also collected simultaneously from China Meteorological Administration. Generalized additive model was used for analyzing the effect of short-term exposure to air pollution on the patients’ hospitalizations and distributed lag non-linear model for the exposure to extremely severe air pollution on the hospitalizations based on the .references from Global Air Quality Guidelines (2021) revised by World Health Organization.

  Results  Increased daily concentrations of air pollutants were associated with increased number of hospitalization of IS patients with hypertension; for every 10 μg/m³ increase of the pollutants, the increment percentage (95% confidence interval 95% CI) of hospitalizations on the day of exposure (lag day 0) was 0.25% (0.17% – 0.34%) for PM_2.5, 0.13% (0.06% – 0.19%) for PM₁₀, 0.85% (0.59% – 1.11%) for NO₂, 0.19% (0.08% – 0.31%) for O₃ and a 1 mg/m³ increase in CO concentration was associated with an increased hospitalization at the percentage of 2.12% (1.41% – 2.83%); for every 10 μg/m³ increase of daily PM_2.5 and PM₁₀, the percentage (95% CI) of hospitalization number increasing at lag day 2 were 0.08% (0.01% – 0.14%) and 0.07% (0.01% – 0.12%), while every 10 μg/m³ increase of daily SO₂ and O₃ were associated declined hospitalization number at lag day 2 at the decrement percentage (95% CI) of 0.61% (0.11% – 1.11%) and 0.12% (0.02% – 0.21%), respectively. The lag day-specific effect of PM_2.5 on hospitalization number increase of the IS patients with hypertension was the strongest at lag day 6, with the relative risk (RR) of 1.05 (95% CI: 1.03 – 1.07); the same effect of PM₁₀, SO₂ and NO₂ was the strongest at lag day 7, with the RR (95% CI) of 1.05 (1.03 – 1.07) , 1.07 (1.04 – 1.10) and 1.02 (1.00 – 1.04); but the same effect was the strongest at lag day 0 for CO. The cumulative effect of exposure to those air pollutants on IS-related hospitalization number of hypertension patients were strongest at lag day 30, with the RR (95% CI) of 1.62 (1.32 – 2.00) for PM_2.5, 1.58 (1.28 – 1.95) for PM₁₀, 1.25 (1.05 – 1.50) for NO₂, , and 1.10 (1.06 – 1.14) for CO, respectively.

  Conclusion  Short-term exposure to air pollution may increase the risk of ischemic stroke hospitalization in hypertensive patients, and the exposures could have relatively longer lag effect.