Ambient pollen exposure and pollen allergy symptom severity in the EPOCHAL study

• Published in: Allergy (Copenhagen) 2024-07, Vol.79 (7), p.1908-1920
• Main Authors: Luyten, Axel, Bürgler, Alexandra, Glick, Sarah, Kwiatkowski, Marek, Gehrig, Regula, Beigi, Minaya, Hartmann, Karin, Eeftens, Marloes
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Aged; Air pollution; Allergens - immunology; allergic rhinitis; Allergies; Environmental Exposure - adverse effects; exposure–response modeling; Female; hay fever; Humans; Male; Middle Aged; Pollen; Pollen - immunology; pollen allergy; Rhinitis, Allergic, Seasonal - diagnosis; Rhinitis, Allergic, Seasonal - etiology; Rhinitis, Allergic, Seasonal - immunology; Seasons; Severity of Illness Index; Symptom Assessment; symptom severity; symptoms; Young Adult
• ISSN: 0105-4538; 1398-9995; 1398-9995
• DOI: 10.1111/all.16130

Background Ambient pollen exposure causes nasal, ocular, and pulmonary symptoms in allergic individuals, but the shape of the exposure–response association is not well characterized. We evaluated this association and determined (1) whether symptom severity differs between subpopulations; (2) how the association changes over the course of the pollen season; and (3) which pollen exposure time lags affect symptoms. Methods Adult study participants (n = 396) repeatedly scored severity of nasal, ocular, and pulmonary allergic symptoms, resulting in three composite symptom scores. We calculated hourly individually relevant pollen exposure to seven allergenic plants (alder, ash, birch, hazel, grasses, mugwort, and ragweed) considering personal sensitization and exposure time lags of up to 96 h. We fitted generalized additive mixed models, with a random personal intercept, adjusting for weather and air pollution as potential time‐varying confounders. Results We identified a clear nonlinear positive association between pollen exposure and ocular and nasal symptom severity in the pollen allergy group: Symptom severity increased steeply with increasing exposure initially, but attenuated beyond approximately 80 pollen/m3. We found no evidence of an exposure threshold, below which no symptoms occur. While recent pollen exposure in the last approximately 5 h affected symptoms most, associations lingered for up to 60 h. Grass pollen exposure (compared to tree pollen) and younger age (18–30 years, as opposed to 30–65 years) were both associated with higher nasal and ocular symptom severity. Conclusions The lack of a threshold and attenuated dose–response curve may have implications for pollen warning systems, which may be revised to include multiday pollen concentrations in the future. The exposure–response relationship between ambient pollen exposure and symptom severity is nonlinear: Symptom severity increases steeply at low pollen levels and attenuates beyond ~80 pollen/m3. Pollen exposure influences symptoms for up to two and a half days after exposure. Pollen allergic participants aged 18–30 years experience the strongest symptoms. Symptoms are stronger in the grass pollen than in the tree pollen season. CI, confidence interval. Abbreviation: CI, confidence interval.