Background: Little is known about the prevalence of allergic diseases in children of different ages. This study aimed to investigate the prevalence of allergic diseases and allergic sensitization in children over a wide age range, with emphasis on the influence of age, gender, and body mass index (BMI).
Methods: In a cross-sectional study, we assessed 5351 Taiwanese children aged 4-18 years using an International Study of Asthma and Allergies in Childhood questionnaire, BMI, and total and specific serum immunoglobulin E.
Results: Forty-eight percent were currently symptomatic for at least one of three allergic diseases. Prevalence of wheeze ever, current wheeze, and diagnosed asthma were 17.0%, 7.5%, and 9.8%, respectively; analogous features for rhinitis were 47.8%, 44.2%, and 39.8%. Allergic sensitization was very common (57.3%). Half of the children (50.6%) with current wheeze had not been diagnosed with asthma by physicians, whereas undiagnosed rates were 32.3% for rhinitis and 25.3% for eczema. The male-to-female prevalence ratios of current wheeze increased with age from <1 at 4-5 years, peaked at 10-11 years (2.24), then reversed to 0.57 at 16-18 years. Childhood wheezing tended to remit with age, but rhinitis and eczema were more persistent. Total immunoglobulin E levels increased with age until 14-15 years, and declined thereafter. Elevated BMI was associated with greater prevalence of wheezing and eczema, with no evidence of significant effect modification by either gender or age. Multivariate analyses revealed that younger age, boys, and obesity were significantly and independently associated with current wheezing in children (all p < .01).
Conclusions: The burden and co-morbidity of childhood allergies are substantial. There are striking age-dependent gender differences in asthma prevalence, exhibiting an inverted U-shaped curve for male-to-female prevalence ratios by age. Obesity is associated with a greater prevalence of asthma in children with no evidence of a significant modulation by either gender or age.