Postcode-Level Variation and Environmental Determinants of Respiratory Allergies in a Large German Cohort

Respiratory allergies (RAs) are common conditions with complex, multifactorial etiologies including environmental influences. However, little is known about their spatial variation at small-area levels in Germany. This study aimed to (1) examine variations in respiratory allergy incidence (RAI) and dispensed prescribed medication rate (DPMR) at the municipal level in Baden-Württemberg from 2012 to 2022; (2) assess associations between RAI, DPMR, and environmental factors in Baden-Württemberg to support targeted prevention strategies.

We used nonparametric tests to examine differences in RAI and DPMR. To assess associations between RAI, DPMR, and environmental factors (e.g., air pollutants, meteorological parameters, pollen), we applied generalized additive two-part models.

Both RAI and DPMR were significantly higher in urban compared to rural areas. The probability of RAs occurrence was significantly associated (p-adjusted < 0.01) with PM₁₀, PM_2.5, temperature, as well as alder and birch pollen. O₃, NO₂, and the interaction O₃*NO₂ were additionally significantly linked to cumulative nonzero RAI. Notably, alder pollen played a major role in determining whether RAs occurred, whereas among diagnosed individuals, PM₁₀ concentration was the strongest determinant. Across air pollutants, reducing PM₁₀ to the quarterly threshold of 15 μg/m³ could reduce RAs onset, especially in children aged 0-9. DPMR models yielded similar results, except for those of NO₂ and the interaction O₃*NO₂.

Reducing alder pollen and PM₁₀ exposure could present the most effective environmental intervention for lowering both RAI and DPMR, particularly in young children. Effective health management is required for affected individuals due to exacerbations caused by O₃ and NO₂.