BACKGROUND: The prevalence of severe asthma is unknown. However, international expert statements estimate that severe asthma represents 5% to 10 % of the entire asthma population.

OBJECTIVE: Based on register data from a nationwide population, we wanted to investigate the prevalence of severe asthma, the extent of asthma control, and contact with specialist care.

METHODS: A descriptive cross-sectional register study was performed. By using a nationwide prescription database, we identified current patients with asthma (age, 18-44 years) in 2010. Severity was classified as severe versus mild-moderate asthma according to the level of antiasthma treatment. We investigated prescription drug use, hospitalizations, emergency department visits, and outpatient clinic visits according to severity.

RESULTS: Among a nationwide population, we identified 61,583 current patients with asthma. Based on the level of antiasthma treatment, 8.1% of identified patients was classified as having severe asthma. Low asthma control (dispensed prescriptions of prednisolone, emergency department visits, hospitalization, or excessive short-acting β₂-agonist use) was more frequent in subjects with severe asthma (36.4% vs 25.2%, P < .0001); 63.8% with severe asthma and low asthma control were not managed by specialist care. Patients with severe asthma with specialist contact more frequently had impaired asthma control compared with subjects not treated by a specialist (44.4% vs 33.1%, P < .0001).

CONCLUSION: Based on the level of treatment, 8.1% of a nationwide population of current patients with asthma was classified as having severe asthma. Low asthma control was more frequent among subjects with severe asthma, and only a minority had access to specialist care. There is room for optimizing asthma management, particularly among patients with severe disease.