Association of short-term exposure to PM2.5 and its components with hospital admission for asthma in Shanghai: a time-stratified case-crossover study.

Introduction: Associations between PM_2.5 and the risk of asthma admission have been established in previous researches. However, evidence about the specific impacts of PM_2.5 components on asthma-related hospitalizations across different populations and environments is limited and inconsistent. The purpose of this study was to examine the association between short-term exposure PM_2.5 and its components with asthma hospital admission.

Method: A total of 930 people hospitalized for asthma were included in the study in Shanghai between December 2018 and December 2022. Air pollution data were assigned to individuals based on their residential address using the Tracking Air Pollution (TAP) platform. A time-stratified case-crossover design and a conditional logistic regression model were used to estimate the risk of asthma admissions related to exposure to PM_2.5. We also conducted stratified analyzes by age, gender, and season.

Results: Each 10 μg/m³ increase in PM_2.5, BC, NO₃^-, NH₄⁺, SO₄^2- and OM at lag-5 day were associated with increased risk of asthma admission, with ORs of 1.04(1.00,1.08), 2.59(0.99,6.76), 1.17(1.02,1.33), 1.33(1.06,1.66), 1.28(1.05,1.55) and 1.16(0.98,1.37), respectively. Stratified analysis showed that PM_2.5 and its components had a more significant impact on the risk of asthma admission for women; individuals aged ≥ 65 years, and during cold seasons at lag-5 day. The results remained stable in the sensitivity analysis.

Conclusion: Short-term exposure to PM_2.5 and its components (NO₃^-, NH₄⁺, SO₄^2-) increases hospitalization risk in asthma patients, particularly among women, elder and those admitted during cold seasons. It provides new insight for reducing the asthma burden associated with particulate air pollution.