Incidence, prevalence, and agreement of parent reported wheezing and physician diagnosed asthma within the first 6 years of life: Results of a prospective birth cohort

Background: Wheezing disorders are heterogenous and common in early childhood, and they may already indicate asthma related problems later on. So far, studies have used different methods to evaluate asthma and wheezing related phenotypes among preschool children. We aimed to describe the occurrence of physician reported asthma, parent reported wheezing, and estimate their agreement within the first six years of life in a large German prospective birth cohort study. Methods: We included 623 children in the analysis. The annual incidence of physician diagnosed asthma and the annual prevalence of parent reported wheezing episodes were obtained periodically. The lifetime prevalence of asthma and wheezing and the proportion of wheezing related phenotypes were calculated in the respective years. The agreement between the two measures was assessed by kappa statistics. Results: The annual and the cumulative incidence of physician reported asthma at four years of age were 11.6% and 32.6%, respectively. The annual prevalence of wheezing declined with older age and reached 8.8% at six years of age. The lifetime prevalence of wheezing ever by three years of age was 32.4% and by six years of age 41.2%. Of the cohort, 11.4% were early persistent wheezers, 21.0% were early transient wheezers, and 8.8% were late onset wheezers. The agreement between physician diagnosed asthma and parent reported wheezing was very low, with kappa values ranging between 0.03 and 0.34. Conclusions: The incidence of physician reported asthma and the prevalence of parent reported wheezing are high among preschool children and correspond with current findings from Western countries. Although wheezing may predict asthma, the low agreement between both outcomes suggests that the comparison of asthma figures from different studies, defined in different manners, should be interpreted with caution.