Early exposure to house-dust mite and cat allergens and development of childhood asthma: a cohort study

Background In a prospective birth-cohort study, we assessed the relevance o f mite and cat allergen exposure for the development of childhood asthma up to age 7 years. Methods Of 1314 newborn infants enrolled in five German cities in 1990, fol low-up data at age 7 years were available far 939 children. Assessments inc luded repeated measurement of specific IgE to food and inhalant allergens, measurement of indoor allergen exposure at 6 months, 18 months, and 3 years of age, and yearly interviews by a paediatrician. At age 7 years, pulmonar y function was tested and bronchial hyper-responsiveness was measured in 64 5 children. Findings At age 7, the prevalence of wheezing in the past 12 months was 10. 0% (94 of 938), and 6.1% (57 of 939) parents reported a doctor's diagnosis of asthma in their children. Sensitisation to indoor allergens was associat ed with asthma, wheeze, and increased bronchial responsiveness. However, no relation between early indoor allergen exposure and the prevalence of asth ma, wheeze, and bronchial hyper-responsiveness was seen. Interpretation Our data do not support the hypothesis that exposure to envi ronmental allergens causes asthma in childhood, but rather that the inducti on of specific IgE responses and the development of childhood asthma are de termined by independent factors.