Sleeping problems and suicide in 75,000 Norwegian adults: a 20 year follow-up of the HUNT I study.

OBJECTIVES: To investigate the association of sleeping problems with suicide risk.

DESIGN: Prospective cohort study linking health survey information on sleep problems to Norway's national mortality registry. Participants were followed up from 1984-6 until December 31, 2004.

SETTING: Residents of Nord-Trøndelag County, Norway, aged 20 years or older in 1984-6.

PARTICIPANTS: Altogether 87,285 people were eligible for the survey and 74,977 (86%) took part in one or more aspects of the study.

INTERVENTIONS: N/A.

MEASUREMENTS AND RESULTS: Three percent of participants experienced sleeping problems every night, 5% experienced problems "often" and 31% reported problems "sometimes." There were 188 suicides during follow-up. Sleeping problems at baseline were strongly associated with subsequent suicide risk. Compared to participants who reported no sleeping problems the age- and sex- adjusted hazard ratios for suicide were 1.9 (CI 1.3-2.6), 2.7 (CI 1.4-5.0), and 4.3 (CI 2.3-8.3) for reporting sleeping problems sometimes, often, or almost every night, respectively. Associations were stronger in younger (< 50 years) participants, but we found no statistical evidence for gender differences. Adjusting for measures of common mental disorder and alcohol use at baseline weakened the associations, but the 3% of subjects with the worst sleep patterns remained at two fold increased risk of suicide.

CONCLUSIONS: Sleeping problems are a marker of suicide risk, mainly due to the presence of both sleeping problems and mixed anxiety and depression. Physicians should be aware of the possible vulnerability for people affected by sleeping problems.