title: The bidirectional relationship between headache and chronic musculoskeletal complaints: an 11-year follow-up in the Nord-Trøndelag Health Study (HUNT).
abstract: OBJECTIVE
  Chronic daily headache (CDH) and chronic musculoskeletal complaints (CMSCs) are associated disorders, but whether there is a causal relationship between them is unclear.
  
  
  OBJECTIVE
  To determine whether CMSCs are associated with the subsequent development of CDH and vice versa.
  
  
  METHODS
  This longitudinal population-based cohort study used data from two consecutive surveys in the Nord-Trøndelag Health Study (HUNT 2 and 3) performed in 1995-1997 and 2006-2008. Amongst the 51 383 participants aged ≥ 20 years at baseline, 41 766 were eligible approximately 11 years later. Of these, 26 197 (63%) completed the questions regarding headache and CMSCs in HUNT 3.
  
  
  RESULTS
  A bidirectional relationship was found between headache and CMSCs. In the multivariate analyses adjusting for known potential confounders, a nearly two fold risk (OR 1.8; 95% CI 1.5-2.3) for developing CDH was found for those with CMSCs at baseline. Vice versa, a similarly elevated risk of CMSCs (OR 1.8; 95% CI 1.2-2.6), and even higher risk of chronic widespread MSCs (OR 2.7; 95% CI 1.6-4.7), was found at follow-up amongst those with CDH at baseline.
  
  
  CONCLUSIONS
  CMSCs predispose to CDH and CDH predisposes to CMSCs 11 years later. This may have relevance to understanding the pathophysiology of these disorders. CMSCs should be treated not only to relieve them but also to prevent the development of CDH, and vice versa.
authors.affiliation: Department of Neuroscience, Norwegian University of Science and Technology, Trondheim, Norway. knut.hagen@ntnu.no
authors.forename: K
authors.initials: K
authors.lastname: Hagen
authors.forename: M
authors.initials: M
authors.lastname: Linde
authors.forename: T J
authors.initials: TJ
authors.lastname: Steiner
authors.forename: J-A
authors.initials: JA
authors.lastname: Zwart
authors.forename: L J
authors.initials: LJ
authors.lastname: Stovner
mesh_terms: D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D020773:Headache Disorders / Q000150:complications* / Q000453:epidemiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D059352:Musculoskeletal Pain / Q000150:complications* / Q000453:epidemiology*; D011795:Surveys and Questionnaires