title: The long-term effect of insomnia on primary headaches: a prospective population-based cohort study (HUNT-2 and HUNT-3).
abstract: OBJECTIVE
  Few prospective studies have evaluated the relationship between insomnia and headache. We aimed to analyze the influence of insomnia at baseline on the risk for headache 11 years later.
  
  
  METHODS
  This longitudinal cohort study included subjects who participated in 2 consecutive surveys of the Nord-Trøndelag Health Study (HUNT-2 and HUNT-3). Among the invited individuals aged 20 years or more in HUNT-2 (n = 92,566) and HUNT-3 (n = 94,194), a total of 26,197 completed the headache section of both surveys. A proxy insomnia diagnosis based on DSM-IV at baseline and ICDH-2-based headache diagnoses at follow-up were derived from questionnaires. Headache-free individuals in HUNT-2 (n = 15,268) were selected for analysis. The relative risks (RRs) for headache in insomniacs were calculated with logistic regression.
  
  
  RESULTS
  The presence of baseline insomnia was associated with a 40% increased risk for headache in HUNT-3 (RR = 1.4, 95% CI = 1.2-1.7). Similar results were found for tension-type headache (TTH), migraine, and non-classified headache. Subjects with insomnia-related working disability had a 60% increased headache risk (RR = 1.6, 95% CI = 1.3-2.1). The RR was larger for migraine (RR = 2.0, 95% CI = 1.3-3.1) than for TTH (RR = 1.5, 95% CI = 1.1-2.1). Insomnia at baseline was related to headache frequency at follow-up for both migraine (P trend = 0.02) and TTH (P trend < 0.001).
  
  
  CONCLUSIONS
  In headache-free subjects, insomnia was associated with an increased risk of headache 11 years later. The association was particularly strong for chronic headache.
authors: Department of Neuroscience, Faculty of Medicine, Norwegian University of Science and Technology, MTFS, Trondheim, Norway.
authors: Siv S
authors: SS
authors: Odegård
authors: Trond
authors: T
authors: Sand
authors: Morten
authors: M
authors: Engstrøm
authors: Lars J
authors: LJ
authors: Stovner
authors: John-Anker
authors: JA
authors: Zwart
authors: Knut
authors: K
authors: Hagen
mesh_terms: D002908:Chronic Disease; D015331:Cohort Studies; D015897:Comorbidity / Q000639:trends; D005260:Female; D051270:Headache Disorders, Primary / Q000453:epidemiology* / Q000503:physiopathology; D006306:Health Surveys; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D007319:Sleep Initiation and Maintenance Disorders / Q000453:epidemiology* / Q000503:physiopathology; D013995:Time; D055815:Young Adult