Previous research suggests a possible link between insomnia and mortality, but findings are mixed and well-controlled studies are lacking. The aim of the current study was to examine the effect of insomnia on all-cause mortality.

Using a cohort design with 14 years follow-up, official registry data on mortality were linked to health information obtained during 1997–99, as part of the community-based Hordaland Health Study (HUSK), in Western Norway. 6,236 participants aged 40–45 completed baseline information included self-reported information on insomnia (defined according to the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-V), sociodemographic factors, health behaviors, obstructive sleep apnea symptoms, sleep duration, sleep medication use, anxiety, depression, as well as a range of somatic diagnoses and symptoms. Height, weight and blood pressure were measured. Information on mortality was obtained from the Norwegian Cause of Death Registry.

Insomnia was found to be a significant predictor of all-cause-mortality (hazard ratio [HR] = 2.86 [95% CI: 1.62–5.03]). Adjusting for several possible confounders did not attenuate the effect (HR=3.07 [95% CI: 1.53–6.15]). Stratifying on sex, the effect was significant in men (adjusted HR=3.93 [95% CI: 1.26–12.19]); but not in women (adjusted HR=2.11 [95% CI: 0.83–5.36]). The mortality risk among participants with both insomnia and short sleep duration (<6.5hours) was particularly high (adjusted HR=4.58 [95% CI: 1.22–17.19]).

Insomnia was associated with a four-fold risk of mortality in men during 14 years follow-up. The risk was especially high in combination with short sleep duration. Establishing prevention strategies and low-threshold interventions should consequently be a prioritized task for public health policy.