title: Lifetime prevalence and characteristics of recurrent primary headaches in a population-based sample of Swedish twins.
abstract: OBJECTIVE
  To examine the lifetime prevalence and other characteristics of recurrent primary headaches in twins.
  
  
  BACKGROUND
  The twin model may provide insights into the role of genetic and environmental influences in headache disorders. However, assumptions as to whether twins are representative of the general population, and whether monozygotic and dizygotic twins are similar have rarely been addressed.
  
  
  METHODS
  The study population consisted of a random sample of 17- to 82-year-old twins from the Swedish Twin Registry (n = 1329). Structured interviews on the telephone by lay personnel and the International Headache Society criteria were used for assessment and diagnosis of recurrent primary headaches. Prevalence data of the general population for migraine and tension-type headache was obtained from various published reports.
  
  
  RESULTS
  A total of 372 subjects (29%) had ever had recurrent headaches. In total, 241 recurrent headache sufferers fulfilled the criteria for migraine or tension-type headache, and the lifetime prevalence was 7.1% for migraine without aura, 1.4% for migraine always with aura, 1.9% for migraine occasionally with aura, 9.4% for episodic tension-type headache, and 1.3% for chronic tension-type headache. The lifetime prevalence of all migraine and all tension-type headache, including another 84 subjects fulfilling all but one of the criteria for migraine or tension-type headache, was 13.8% and 13.5%, respectively. The corresponding prevalence risk for women was 2.4 (95% confidence interval [CI] 1.7, 3.4) and 1.5 (95% CI 1.1, 2.1), respectively. Zygosity was not a significant predictor for migraine. In tension-type headache, the prevalence risk for dizygotic twins and unlike-sexed twins as compared with monozygotic twins was 1.9 (95% CI: 1.2, 3.1) and 1.8 (95% CI: 1.1, 2.9), respectively.
  
  
  CONCLUSIONS
  There is no twin-singleton or monozygotic-dizygotic difference for the risk of migraine. In tension-type headache, twins seem to have a lower risk than singletons, and this is especially true for monozygotic twins.
authors.affiliation: Division of Neurology, Neurotec, Karolinska Institutet, Huddinge University Hospital, Stockholm, Sweden.
authors.forename: Dan A
authors.initials: DA
authors.lastname: Svensson
authors.forename: Karl
authors.initials: K
authors.lastname: Ekbom
authors.forename: Bo
authors.initials: B
authors.lastname: Larsson
authors.forename: Elisabet
authors.initials: E
authors.lastname: Waldenlind
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004200:Diseases in Twins / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008881:Migraine Disorders / Q000453:epidemiology* / Q000209:etiology; D015995:Prevalence; D012008:Recurrence; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology; D018781:Tension-Type Headache / Q000453:epidemiology* / Q000209:etiology; D014427:Twins