title: The epidemiology of insomnia: associations with physical and mental health. The HUNT-2 study.
abstract: OBJECTIVE
  The aim of the present study was to examine the association of insomnia symptoms with demographic and physical and mental conditions in a large population-based study.
  
  
  METHODS
  Cross-sectional data on insomnia and comorbid conditions were gathered from 47,700 individuals aged 20-89 in Norway. Comorbid conditions included anxiety and depression and the following physical conditions: asthma, allergy, cancer, hypertension, diabetes, migraine, headache, osteoporosis, fibromyalgia rheumatoid arthritis, arthrosis, Bechterew's disease, musculoskeletal disorders, and obesity (body mass index >30).
  
  
  RESULTS
  Insomnia symptoms were found in 13.5% of the population and were more prevalent among women, older adults, and in individuals with less education. Reporting insomnia symptoms significantly increased the associations with a range of conditions, especially mental conditions, pain conditions with uncertain etiology and, to a lesser extent, chronic pain conditions. These findings remained significant also when adjusting for a range of potential confounders, whereas the association between insomnia and somatic conditions was largely reduced to a nonsignificant level in the fully adjusted analyses.
  
  
  CONCLUSIONS
  This study demonstrates that insomnia symptoms are associated with a range of different conditions. The findings suggest that the independent contribution of insomnia is strongest on conditions characterized by some level of psychological or psychosomatic properties.
authors.affiliation: Department of Clinical Psychology, Faculty of Psychology, University of Bergen, Bergen, Norway. borge.sivertsen@psykp.uib.no
authors.forename: Børge
authors.initials: B
authors.lastname: Sivertsen
authors.forename: Steinar
authors.initials: S
authors.lastname: Krokstad
authors.forename: Simon
authors.initials: S
authors.lastname: Øverland
authors.forename: Arnstein
authors.initials: A
authors.lastname: Mykletun
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D001008:Anxiety Disorders / Q000175:diagnosis / Q000453:epidemiology*; D003430:Cross-Sectional Studies; D003866:Depressive Disorder / Q000175:diagnosis / Q000453:epidemiology*; D005260:Female; D006304:Health Status; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012720:Severity of Illness Index; D017678:Sex Distribution; D007319:Sleep Initiation and Maintenance Disorders / Q000453:epidemiology*; D055815:Young Adult