Background:
Studies have linked daily pollen counts to respiratory allergic health outcomes but few have considered allergen levels.
Objective:
This study assessed associations of grass pollen counts and allergen levels (Phl p 5) with 1) respiratory allergic health symptoms in a panel of 93 adults with moderate-severe allergic rhinitis and 2) daily asthma hospital admissions in London, UK.
Methods:
Daily symptom and medication scores were collected from adult participants in an allergy clinical trial. Daily counts of asthma hospital admissions in the London general population were obtained from Hospital Episode Statistics data. Daily grass pollen counts were measured using a volumetric air sampler, and novel Phl p 5 levels, using a Chemvol high-volume cascade impactor and ELISA analyses (May-August). Associations between the two pollen variables and daily health scores (dichotomized based on within-person 75th percentiles) were assessed using generalized estimating equation logistic models, and with asthma hospital admissions using Poisson regression models.
Results:
Daily pollen counts and Phl p 5 levels were each positively associated with reporting a high combined symptom and medication health score in separate models. However, in mutually adjusted models including terms for both pollen counts and Phl p 5 levels, associations remained for Phl p 5 levels (odds ratio [95% confidence intervals]: 1.18 [1.12, 1.24]) but were heavily attenuated for pollen counts (1.00 [0.93, 1.07]). Similar trends were not observed for asthma hospital admissions in London.
Conclusion:
Grass allergen (Phl p 5) levels are more consistently associated with allergic respiratory symptoms than grass pollen counts.