The epidemiology of insomnia: Associations with physical and mental health. The HUNT-2 study

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. Conclusion: 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. (C) 2009 Elsevier Inc. All rights reserved.