Prevalence of severe asthma – results from a population-based study

Abstract

Introduction: Research on severe asthma based on population samples is scarce and defining severe asthma in epidemiological samples is a challenge. Aims and Objectives: To investigate the prevalence and clinical features of severe asthma in a population-based study. Methods: In the West Sweden Asthma Study, a randomly selected sample (N=1172) and a separate asthma sample (N=744) underwent clinical examinations. Severe asthma required at least medium dose inhaled corticosteroids (ICS) plus a second controller or oral corticosteroids (OCS) based on GINA steps 4 and 5. The prevalence was calculated in the random sample and clinical features were assessed in the asthma sample. Asthma control was assessed with the GINA Symptom Control Tool. Results: In the random sample (mean age 50.4y, 54% women), 138 subjects had current asthma (12%) and 12 (1%) had severe asthma. In the asthma sample, 94.4% of the 72 subjects with severe asthma used ICS + LABA, 4.2% used ICS + inhaled anticholinergic and 1.4% used ICS + OCS. Subjects with severe asthma were older vs. non-severe asthma (N=672), 52.1y vs. 47.6y (p=0.02). They had both lower FEV1% of predicted, 88% vs. 97% (p Conclusions: The prevalence of severe asthma on population level was 1%. Subjects with severe asthma had poorer lung function and asthma control and more symptoms than subjects with non-severe asthma.