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

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.

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).

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.

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.