medwireNews: Month of birth closely correlates with the prevalence of bronchial asthma (BA), a major study of Taiwanese children has found.
The prevalence of BA was highest among children born in the autumn and lowest among those born in spring. And markers of allergy followed a similar pattern, adding weight to the result.
“[A] greater understanding of plausible allergens will help decrease the incidence of BA in children’s early life in the future,” write Wei-Pin Chang (Yuanpei University, Hsinchu, Taiwan) and colleagues in PLoS ONE.
The team analyzed data on 104,455 children who were aged between 7 and 15 years in 2010 and had at least two hospital visits or at least one hospital admission for BA, atopic dermatitis (AD), or allergic rhinitis (AR).
They found that the prevalence of BA, but not AD or AR, significantly correlated with the children’s month of birth, being lowest among those born in May (7.21%) and highest among those born in October (10.59%).
The same pattern emerged when children were grouped according to season of birth, with those born between August and October having a 13% higher prevalence of moderate-to-severe BA than those born between February and April, after adjusting for confounders.
Risks for children born in summer and winter were comparable to those for children born in spring.
Interestingly, levels of two allergic markers – total immunoglobulin E and ImmunoCAP allergen – fluctuated with season of birth, again being significantly higher in children born in autumn than in those born in other seasons.
Attempting to explain their findings, Chang and co-authors note that cold temperatures are known to increase the risk for childhood asthma, possibly by inducing hypersecretion from bronchial epithelial cells. Since children born in autumn will experience cold weather in their first months of life, this could potentially lead to AD.
Another possible mechanism is viral infection in early life, which is associated with airway obstruction and asthma in children; respiratory syncytial virus peaks in the community in July to October, which would be consistent with the findings of the current study.
While admitting that more research is needed, the authors conclude: “The relationship between season of birth and asthma might be one of the environmental factors in this complex disease.”
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