Asthma phenotypes and lung function up to 16years of agethe BAMSE cohort

BackgroundAsthma is a disease affecting many locations throughout the airway. Most studies have used spirometry as the primary assessment of airway obstruction, a method that may be less sensitive in regard to peripheral airway obstruction. The aim of this study was to elucidate the associations between asthma phenotypes based on age of onset and duration of symptoms, and (i) spirometry and (ii) small airway involvement measured by impulse oscillometry (IOS) in adolescence. MethodsChildren and adolescents taking part in BAMSE, a prospective birth cohort study, performed spirometry at 8 and 16years and IOS at 16years of age. Based on data collected in questionnaires, children were categorized into the following groups: never asthma', early transient asthma', early persistent asthma', and late onset asthma'. ResultsCompared with the never asthma group, all asthma groups were associated with lower FEV1 at 16years of age (early transient119ml, 95% confidence interval -204 to -34; early persistent410ml, 95%CI -533; -287; and late onset148ml, 95%CI -237; -58). Between 8 and 16years, significantly less increase in FEV1 was observed in the early persistent and late onset groups. The small airway index R5-20' was significantly associated with active asthma at 16years, but not transient asthma. ConclusionsAll asthma phenotypes studied were negatively associated with FEV1 in adolescence. IOS measurements indicated that active asthma could be associated with small airway impairments. These results provide new insights into the physiology underlying wheezing phenotypes based on age of onset and duration of disease.