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 > or =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.