Association between hospital-diagnosed sleep disorders and suicide: a nationwide cohort study

Study Objectives Sleep disorders are related to mental disorders. Yet few studies have examined their association with suicide. We examined whether males and females diagnosed with sleep disorders had higher rates of suicide than individuals not diagnosed with sleep disorders. Methods In a cohort study, nationwide data on all males and females aged over 15 years living in Denmark during 1980-2016 were analyzed. Sleep disorders were identified through diagnoses recorded during contacts to somatic hospitals. Incidence rate ratios (IRR) were estimated using Poisson regression models and adjusted for covariates. Results In all, 3 674 563 males and 3 688 164 females were included, of whom 82 223 (2.2%, mean age: 50.2 years, SD: 17.5) males and 40 003 (1.1%, mean age: 50.6 years, SD: 19.9) females had sleep disorder diagnoses. Compared with those with no sleep disorders, the adjusted IRR for suicide were 1.6 (95% CI, 1.4 to 1.7) and 2.2 (95% CI, 1.8 to 2.6) for males and females with sleep disorders, respectively. Excess rates for narcolepsy were found for males (IRR: 1.2, 95% CI, 1.0 to 1.5) and females (IRR: 3.3, 95% CI, 3.0 to 4.1), and for sleep apnea in males (IRR: 1.8, 95% CI, 1.5 to 2.2). A difference with respect to age and sex was observed (p < 0.001) between males and females. Males and females had IRR of 4.1 (95% CI, 3.1 to 5.5) and 7.0 (95% CI, 4.8 to 10.1), during the first 6 months after being diagnosed with a sleep disorder. Conclusions Sleep disorders were associated with higher suicide rates even after adjusting for preexisting mental disorders. Our findings suggest attention toward suicidality in patients with sleep disorders is warranted.