Objective, but Not Self-reported, Short Sleep Duration Increases Mortality Risk in Adults with Insomnia Symptoms: The Wisconsin Sleep Cohort

STUDY OBJECTIVES: Insomnia with objective short sleep duration has been reported to be associated with cardiometabolic comorbidities. We aimed to investigate the association between insomnia symptoms with objective or self-reported sleep duration and mortality in a general population sample. METHODS: From the Wisconsin Sleep Cohort, 373 participants with insomnia symptoms and 394 participants without insomnia symptoms with a median follow-up duration of 8 years were included. Insomnia symptoms were defined as the presence of difficulty in falling sleep, maintaining sleep or early awakening for more than 5 times/month. Objective short sleep duration was defined as total sleep time < 6 hours based on polysomnography. Self-reported short sleep duration was defined as < 7 hours. RESULTS: Insomnia symptoms with objective short sleep duration were associated with a 2.6-fold higher risk of all-cause mortality (hazard ratio [HR]=2.57, 95% confidence interval [95%CI]=1.12-5.89) compared to participants without insomnia symptoms and normal sleep duration (>6 hours) after controlling for confounders. Furthermore, participants with insomnia symptoms and normal sleep duration or with objective short sleep duration but without insomnia symptoms were not associated with increased risk of all-cause mortality. Finally, insomnia symptoms with self-reported short sleep duration were not associated with risk of all-cause mortality. CONCLUSIONS: Our findings support that insomnia with objective short sleep duration is the more severe insomnia phenotype. Objective short sleep duration appears to be a valid marker of the biological severity of insomnia.