Demographic heterogeneity in health impacts of air pollution exposure on respiratory infections in Eastern China: A six-year multicity study

Respiratory infections (RIs) are a significant burden on public health, and the COVID-19 pandemic complicated their management. Here, we investigate associations between air pollution exposure and RI health outcomes. We analysed 8.2 million RI episodes (limited to respiratory diseases, as classified by the 10th revision of the International Classification of Diseases: J00-J22) in Taizhou and Huzhou (2017–2022), collapsing repeat visits within 14 days. A generalized additive model (GAM) was used to explore the relationships between daily 24-h average Particulate Matter with a diameter < 2.5 µm (PM2.5) and nitrogen dioxide (NO2) exposure (single lags [0–3] and moving averages over the same period) and health outcomes. Additionally, multivariable logistic regression was employed to assess the risk (defined as exceeding the median hospital stays and severe illness during hospitalization) attributable to demographic factors among inpatient cases. The study encompassed 8,198,574 cases admitted; males constituted 51.2% and children under 5 years comprised 31.2%. Children and adolescents aged 5–18 exhibited a 4.965% (95% Confidence Interval [CI]: 4.449–5.483) increase in daily admissions for every 10 μg/m3 rise in PM2.5 and a 7.789% (7.092–8.491) increase for the same change in NO2. For each 10 μg/m3 increase in PM2.5, the length of stay (LOS) increased by 6.435 days for children under 5 and 11.206 days for those over 65. Urban residents showed a longer LOS (adjusted odds ratio, aOR: 1.079, 1.047–1.112) but a reduced risk of severe illness (aOR: 0.833, 0.772–0.899) compared to their rural counterparts. The elderly (aged 65 and above) demonstrated the highest risk of severe illness compared to adults aged 19–34; this was particularly pronounced during the pandemic response phase (aOR: 11.900, 7.928–18.960). Air pollutant levels are correlated with a spectrum of respiratory health outcomes, and these associations exhibit substantial demographic disparities. The risk of severe illness among children under 5 years and the elderly was significantly elevated, underscoring the urgent need for health authorities to formulate targeted strategies aimed at protecting these at-risk groups.