PURPOSE OF THE STUDY.
To determine if exposure to higher concentrations of pollen within the first 3 to 6 months of life increases the risk of eczema, sensitization to food or aeroallergens at 2 years old, and asthma or hayfever at 6 to 7 years old.
The study used the Melbourne Atopy Cohort Study, a longitudinal birth cohort study, comprising 620 participants who were enrolled before birth. Children were born between 1990 and 1994 and had a family history of allergic disease in at least 1 first-degree relative.
Researchers identified those born “inside” or “outside” pollen season (defined as September to January in Melbourne) and used daily pollen counts to calculate cumulative pollen exposure in the first 6 months of each child’s life. Using logistical regression models, they examined the cohort at 2 years old for associations of pollen exposure with eczema or allergic sensitization (skin prick test >3 mm to at least 1 of the following: cow’s milk, egg white, peanut, house dust mite, rye grass, and cat dander) and again at 6 to 7 years for diagnoses of asthma or hayfever.
At age 2 years, birth during pollen season was not associated with eczema or with sensitization to food or aeroallergens; however, cumulative exposure to pollen at 6 months was associated with aeroallergen sensitization with the highest risk being at 3 months (adjusted odds ratio [aOR] = 1.34, 95% confidence interval [CI] 1.06–1.72, P < .05). At 6 to 7 years old, cumulative pollen exposure at 3 months was associated with hayfever (aOR = 1.14, 95% CI 1.009–1.29, P < .05), and exposure at 4 to 6 months was associated with asthma only (aOR = 1.35, 95% CI 1.07–1.72, P < .05). Cumulative exposure at 6 months increased odds of hayfever, asthma, and both hayfever and asthma (P < .05).
Persistent exposure to pollen in infancy appears to increase risk of developing asthma and hayfever later in life.
This study is the first to show an association between early continuous pollen exposure and subsequent development of asthma and hayfever later in childhood. Interestingly, children without family history of asthma were also noted to have an increased risk of allergic disease if born inside pollen season. Given ambient pollen exposure, the usefulness of avoidance recommendations to modify risk is unclear, however.
- Copyright © 2013 by the American Academy of Pediatrics