title: Prevalence of primary chronic headache in a population-based sample of 30- to 44-year-old persons. The Akershus study of chronic headache.
abstract: BACKGROUND
  Prevalence data on primary chronic headache in the general population based on clinical interviews by physicians are lacking.
  
  
  METHODS
  In a cross-sectional epidemiological survey, a random sample of 30,000 persons from Akershus County, aged 30-44 years, were sent a postal questionnaire. Those with self-reported chronic headache within the last month and/or year were invited to a semi-structured diagnostic interview and a physical and neurological examination conducted by 2 neurological residents with experience in headache diagnostics. The diagnoses were made according to the International Classification of Headache Disorders, 2nd edition, 2004, and relevant revisions.
  
  
  RESULTS
  The questionnaire response rate was 71%, and the participation rate of the interview was 74%. The 1-year prevalence of primary chronic headache was 2.9%. Chronic tension-type headache (CTTH) and probable chronic tension-type headache (pCTTH) had 1-year prevalences of 1.6 and 1.2%, respectively. The prevalences of other primary chronic headaches were: chronic migraine (CM) 0.01%, probable CM 0.09% and other subtypes 0.04%. Co-occurrence of migraine was frequent, as 42% with CTTH and 55% with pCTTH had migraine.
  
  
  CONCLUSIONS
  Primary chronic headache is prevalent in the general population. The majority has CTTH or pCTTH, while CM and other primary chronic headaches are rare.
authors.affiliation: Head and Neck Research Group, Akershus University Hospital, Nordbyhagen, Norway. r.berling.grande@medisin.uio.no
authors.forename: Ragnhild Berling
authors.initials: RB
authors.lastname: Grande
authors.forename: Kjersti
authors.initials: K
authors.lastname: Aaseth
authors.forename: Pål
authors.initials: P
authors.lastname: Gulbrandsen
authors.forename: Christofer
authors.initials: C
authors.lastname: Lundqvist
authors.forename: Michael Bjørn
authors.initials: MB
authors.lastname: Russell
mesh_terms: D000328:Adult; D000367:Age Factors; D002908:Chronic Disease; D003430:Cross-Sectional Studies; D005260:Female; D020773:Headache Disorders / Q000175:diagnosis / Q000453:epidemiology*; D006801:Humans; D007407:Interviews as Topic; D008297:Male; D008881:Migraine Disorders / Q000175:diagnosis / Q000453:epidemiology; D009460:Neurologic Examination; D009664:Norway / Q000453:epidemiology; D010808:Physical Examination; D011159:Population Surveillance / Q000379:methods; D015995:Prevalence; D012737:Sex Factors; D011795:Surveys and Questionnaires