Cluster analysis of Finnish population-based adult-onset asthma patients.

BACKGROUND: Phenotypes of adult asthma have been identified in previous studies but rarely in population-based settings.

OBJECTIVE: To identify clusters of adult-onset asthma, in a Finnish population-based study on subjects born before 1967.

METHODS: We used population-based data from 1350 asthmatics with adult-onset asthma (Adult Asthma in Finland) from Finnish national registers. Twenty-eight covariates were selected based on literature. Number of covariates was reduced by using factor analysis before cluster analysis.

RESULTS: Five clusters (CLU1 - CLU5) were identified, three clusters with late-onset adult asthma (onset ≥40 years) and two clusters with onset at earlier adulthood (<40 years). Subjects in CLU1 (n=666) had late-onset asthma, were non-obese, symptomatic, predominantly female with few respiratory infections during childhood. CLU2 (n=36) consisted of subjects with earlier-onset asthma, who were predominantly female, obese with allergic asthma, and recurrent respiratory infections. Subjects in CLU3 (n=75) were non-obese, older and predominantly men with late-onset asthma, smoking history, co-morbidities, severe asthma, least allergic diseases, low education, many siblings, and childhood in rural areas. CLU4 (n=218) was a late-onset cluster consisting of obese females with co-morbidities, asthma symptoms, and low education level. Subjects in CLU5 (n=260) had earlier onset asthma, were non-obese, predominantly allergic females.

CONCLUSIONS: Our population-based adult-onset asthma clusters take into account several critical factors such as obesity and smoking, and identified clusters that partially overlap with clusters identified in clinical settings. Results give us more profound understanding of adult-onset asthma phenotypes and support personalized management.