Risk factors and characteristics of early-onset asthma in Taiwanese children.

Background and Purpose: Early-onset asthma has been reported to be associated with a family history of allergy and exposure to environmental factors. This study was designed to evaluate the relationship between age of onset of asthma and genetic and environmental factors with asthma severity in Taiwanese children. Methods: A group of 352 children with asthma (220 males and 132 females), ranging in age from 5 to 15 years, were enrolled in this study. The subjects were divided into 2 groups: early-onset asthma (up to and including age 3) and late-onset asthma. General characteristics including family history of allergies and exposure to domestic pets and tobacco smoke were recorded. The subjects underwent pulmonary function testing and analysis of serum immunoglobulin E (IgE), eosinophil counts, and specific IgE for common allergens. Results: Early-onset asthma was present in 149 subjects and late-onset asthma in 203. Family history of allergies included a sibling with asthma or urticaria predisposed to early-onset asthma (asthma, p=0.034; urticaria, p=0.024). Food and milk allergen sensitization were more common in early-onset asthma (food allergens, p=0.025; milk, p=0.034). Children with early-onset asthma had higher eosinophil counts (p=0.041). However, there was no correlation between age at onset and pulmonary function testing, the levels of total IgE and IgE specific for Dermatophagoides pteronyssinus or Dermatophagoides farinae. Conclusions: A history of asthma or urticaria in a sibling is a risk factor for early-onset asthma. A greater prevalence of food allergen sensitization and high eosinophil counts are characteristic of early-onset disease.