(A-056) The Association Between Long-Term Outdoor Air Pollution Exposure and Inhaler Prescriptions in General Practices in England

Background: The concentrations of air pollutants have been linked to inhaler prescriptions in some regions of England, but the nationwide study remains limited. Furthermore, the impacts of air pollutants on the respiratory system could be varied. This study aims to assess the association between inhaler prescription volumes and air pollutants across general practices (GPs) in England, with further investigation into pharmacological subgroups and the potential modifying effect of socioeconomic status (SES).

Methods: A cross-sectional study used English prescribing data and included GPs that issued inhaler prescriptions in 2023. Annual mean concentrations of PM₁₀, PM₂.₅, NO, NO₂, SO₂, and the number of days with an 8-hour max ozone concentration >120 µg/m³ were extracted from the Department for Environment Food and Rural Affairs according to each GP’s location. Inhaler prescription volumes (DDD/1,000 registrants/year) were calculated for total inhalers and three subtypes: preventive, reliever, and corticosteroid-only. Linear mixed-effects models with random intercepts were used to assess associations between air pollution and inhaler prescribing, adjusting for cluster effects of Integrated Care Boards (ICBs), SES, demographics, and disease prevalence. Interaction terms between pollutants and IMD deciles were tested using likelihood ratio tests.

Results: A total of 6,265 GPs across 42 ICBs in England were included. The median number of registrants per practice was 8,562 (IQR: 5655,12348). Higher annual concentrations of PM₁₀, NO₂, and SO₂ were positively associated with increased prescriptions, with estimated increases of 280.06 (95% CI：86.7,473.4), 446.2 (95% CI：57.8,834.5) and 1,036.5 (95% CI：750.0,1322.1) DDD/1,000 registrants/year for 1 μg/m³ increase in the concentration of PM₁₀, NO₂, and SO₂. In contrast, higher levels of NOₓ and O₃ were associated with lower prescribing volumes (NOₓ: β=437, 95%CI: -488.1, -97.3；O3: 292.7, 95%CI: -488.1,-97.3). No significant association was observed between PM₂.₅ and inhaler prescription volume. SO₂ demonstrated a consistent positive association across all inhaler subtypes. Furthermore, significant interaction effects were observed between PM₁₀, O₃, and SO₂ with SES(PM10：p = 0.0966；O₃：p = 0.0034；SO₂：p = 0.0013).

Conclusions: Long-term exposure to ambient pollutants, particularly SO₂ and PM₁₀, is associated with increased prescribing of inhaled medications in primary care, and this association is modified by area-level deprivation.