Prevalence of asthma phenotypes in different age groups – a prospective study

<bold>Introduction:</bold> Asthma is a chronic heterogeneous disease with different pathophysiological pathways and different phenotypes. Age is one of strongest determinants of childhood asthma phenotype, and involves pathophysiological events, exposure and natural history determinants. <bold>Aim:</bold> To examine the prevalence of clinical asthma phenotypes in different age groups and monitor their stability during a 5-year follow-up. <bold>Methods:</bold> A total of 152 children with newly diagnosed asthma were followed for five years. They were divided into 3 groups: preschool children (3-5 years), school children (6-12 years) and adolescents. The frequency of symptoms and their triggers were monitored for 5 years. Viral induced asthma (VIA) was defined if the main trigger during the study period was viral infections, and exercise induced asthma (EIA) if the majority of symptoms were caused by exercise. If most symptoms were not related to exercise or viral infections, allergic asthma was diagnosed if associated with sensitization to aeroallergens and non-allergic asthma if no allergy was detected. <bold>Results:</bold> Allergic asthma was the most prevalent phenotype (69.7%), even in preschool children (65.3%). The mean age of children with allergic asthma was not statistically significantly different from the mean age of children with other asthma phenotypes. Most children had a stable phenotype, while 20 children (13.6%) had characteristics of at least two phenotypes during the observation period. <bold>Conclusion:</bold> Allergic asthma is the most common phenotype in children regardless of age. Clinical asthma phenotypes have good longitudinal stability. Multicenter cohort studies are needed for better understanding of asthma phenotypes in children.