Prevalence, severity and determinants of asthma in Danish five-year-olds

Background: The prevalence of asthma and wheeze is increasing. Aim: To study the annual and cumulative prevalence of asthma and wheeze in 5-y-old Danish children. Methods: We obtained data on 3052 ( 82.0% of eligible) Danish children by a postal parental questionnaire including ISAAC questions regarding respiratory symptoms and our own questions on sociodemography and tobacco exposure. Results: "Wheeze ever" was reported in 38.3%, "doctor-diagnosed asthma ever" in 10.5%, "childhood bronchitis ever" in 30.0%, "current wheeze'' ( < 12 mo) in 19.7%, and being "severe" ( > 3 episodes) in 3.9% of the children. Current wheeze was associated with male gender ( OR 1.63, 95% CI 1.35 - 1.96), low parental post-primary education ( OR 1.29, 95% CI 1.02 - 1.63 for < 3 y vs >= 3 y) and current maternal smoking ( OR 1.69, 95% CI 1.39 - 2.04). "Severe current wheeze" was recognized as asthma in six and childhood bronchitis in three of 10 cases. Nearly all diagnosed asthmatics had suffered wheeze, two-thirds recently. Conclusion: We found a high prevalence of asthma and wheeze in Danish late-preschool children, associated with male gender, current maternal tobacco smoking and low parental post-primary education. The majority of children with current wheeze had an early onset, and severe early symptoms tended to persist. Used with consideration, the label "childhood bronchitis" seems purposeful.