Severe Asthma in a General Population Study: Prevalence and Clinical Characteristics

Abstract

Purpose

Current guidelines primarily use medication levels to distinguish severe asthma from other types of asthma. In addition, severe asthma must also be uncontrolled at high-intensity treatment or become uncontrolled if treatment level is decreased. To date, only a few studies have used this definition to investigate the prevalence and clinical characteristics of severe asthma in population-based samples. Therefore, the aim of this study was to evaluate the prevalence and clinical characteristics of individuals with severe asthma in the population-representative West Sweden Asthma Study.

Materials and Methods

In this cross-sectional population-based study, a randomly selected sample (n=1172) and a separate asthma sample (n=744) underwent clinical examinations, completed a structured interview and responded to questionnaires. Severe asthma was defined as at least one feature of uncontrolled asthma despite treatment in line with the Global Initiative for Asthma (GINA) steps 4/5. This treatment level required a minimum medium dose of inhaled corticosteroids (ICS) plus a second controller or oral corticosteroids.

Results

The prevalence of severe asthma was 1.1% in the adult random sample and 9.5% within the asthma sample. Individuals with severe asthma were older and had more symptoms, activity limitations, heart disease and blood neutrophils compared to those with other asthma. They also had lower lung function and despite these impairments, 32% did not have annual contact with a healthcare provider.

Conclusion

The prevalence of severe asthma was higher compared to previous studies, and many individuals with severe asthma did not have regular contact with healthcare providers. Due to the high burden of symptoms and impairments for individuals with severe asthma, it is important that the healthcare system implement strategies to improve follow-up and evaluate these patients according to existing guidelines.

Keywords:

• asthma epidemiology
• asthma control
• asthma-medication
• asthma severity symptoms
• lung function

Acknowledgments

We would like to acknowledge The Herman Krefting Foundation for Allergy and Asthma Research, the Swedish Heart-Lung Foundation and the ALF-agreement between the Swedish government and the Västra Götaland Regional Council for unrestricted funding of the study. We also thank the study staff and participants for their involvement in the study.

Disclosure

Ms Lina Rönnebjerg reports personal fees from AstraZeneca, outside the submitted work. Professor Hannu Kankaanranta reports personal fees, non-financial support from AstraZeneca, Orion Pharma; personal fees from Boehringer-Ingelheim, Chiesi Pharma, GlaxoSmithKline, MSD, Mundipharma, Novartis, and Sanofi, outside the submitted work. Dr Helena Backman reports personal fees from Astra Zeneca and Boehringer Ingelheim, outside the submitted work. Professor Bo Lundbäck reports grants from ThermoFisher, personal fees from Sanofi, outside the submitted work. The authors report no other conflicts of interest in this work.