title: The prevalence of severe asthma and low asthma control among Danish adults.
abstract: 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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Respiratory Research Unit, Department of Respiratory Medicine L, Bispebjerg Hospital, Copenhagen, Denmark. Electronic address: annavonbulow@gmail.com.
authors.forename: Anna
authors.initials: A
authors.lastname: von Bülow
authors.affiliation: Department of Public Health, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Margit
authors.initials: M
authors.lastname: Kriegbaum
authors.affiliation: Respiratory Research Unit, Department of Respiratory Medicine L, Bispebjerg Hospital, Copenhagen, Denmark.
authors.forename: Vibeke
authors.initials: V
authors.lastname: Backer
authors.affiliation: Respiratory Research Unit, Department of Respiratory Medicine L, Bispebjerg Hospital, Copenhagen, Denmark.
authors.forename: Celeste
authors.initials: C
authors.lastname: Porsbjerg
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000553:Ambulatory Care / Q000706:statistics & numerical data; D018927:Anti-Asthmatic Agents / Q000627:therapeutic use*; D001249:Asthma / Q000175:diagnosis / Q000188:drug therapy* / Q000453:epidemiology* / Q000503:physiopathology; D003430:Cross-Sectional Studies; D003718:Denmark / Q000453:epidemiology; D011307:Drug Prescriptions; D017723:Drug Utilization Review; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data; D005260:Female; D019538:Health Care Surveys; D006295:Health Resources / Q000706:statistics & numerical data*; D006760:Hospitalization; D006801:Humans; D008168:Lung / Q000187:drug effects* / Q000503:physiopathology; D008297:Male; D015995:Prevalence; D012017:Referral and Consultation / Q000706:statistics & numerical data; D012042:Registries; D012720:Severity of Illness Index; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D018927:Anti-Asthmatic Agents
keywords: Asthma control; Asthma management; Prescription data; Severe asthma; asthma