Short-term effects of air pollutants on asthma hospitalizations in a megacity in North China (2016–2021): a time-series study

Asthma remains a major global health challenge, with air pollution triggering severe exacerbations. Current studies have reported inconsistent results due to limited pollutant coverage, small sample size, or focus on mild cases. Beijing, with extreme air pollution, clear seasons, and dense population, provides an ideal setting to examine pollution-hospitalization relationships for asthma. Using 2016–2021 data from 12 Beijing monitoring stations, we analyzed daily particulate matter ≤ 2.5 μm (PM₂.₅), particulate matter ≤ 10 μm (PM₁₀), sulfur dioxide (SO₂), nitrogen dioxide (NO₂) and carbon monoxide (CO) levels. A generalized additive time-series model with a Poisson distribution was used to investigate relative risks (RRs) and 95% confidence intervals (CIs) for asthma hospitalizations, stratified by sex, age, atopic status and season. All five air pollutants were significantly associated with the risk of asthma hospitalization, and each exhibited lagged effects. Per interquartile range (IQR) increase in pollutant concentration, RRs were: PM₂.₅ 1.018 (95% CI: 1.005–1.031), PM₁₀ 1.012 (1.003–1.021), SO₂ 1.019 (1.010–1.028), NO₂ 1.059 (1.041–1.077), and CO 1.025 (1.014–1.036). Strongest associations occurred in winter. Females, the elderly, and non-atopic individuals were most vulnerable. Short-term exposure to air pollutants increased asthma hospitalization risks, with amplified effects in females, the elderly, and non-atopic individuals. These findings highlight critical exposure windows and vulnerable populations, guiding targeted interventions. The registration number of this study in China’s National Medical Research Registration and Filing Information System is MR-11-23-009586.