BOSTON—Insomnia with objective short sleep duration (ie, less than six hours) is not associated with an elevated risk of all-cause mortality, according to research presented at the 31st Annual Meeting of the Associated Professional Sleep Societies. Short sleep duration alone is associated with a higher risk of death, however.
To quantify the association between insomnia with objective short sleep duration and all-cause mortality, Suzanne Bertisch, MD, MPH, Assistant Professor of Medicine at Harvard Medical School and Clinical Investigator at Beth Israel Deaconess Medical Center in Boston, and colleagues conducted a time-to-event analysis of the Sleep Heart Health Study data. This prospective, community-based cohort study enrolled 6,441 participants age 40 and older between 1995 and 1998. At baseline, researchers administered questionnaires that queried participants about sleep symptoms, sleep patterns, medication, and medical history. In addition, participants underwent anthropometry and blood pressure measurements and had one night of unattended polysomnography at their home by certified and trained technicians. Researchers followed participants for a median of 11.6 years.
The primary exposure for Dr. Bertisch’s analysis was insomnia with short sleep duration. The investigators defined insomnia as self-report of difficulty falling asleep, difficulty getting back to sleep, early morning awakenings, or use of a sleeping pill for 16 to 30 nights/month. Short sleep duration was defined as total sleep time of less than six hours on single-night polysomnography. Covariates of interest included sex, race, smoking status, history of cardiovascular disease, apnea–hypopnea index, BMI, antidepressants used in the previous two weeks, hypertension, and diabetes.
Investigators used the propensity-score-adjusted Cox proportional hazards model to estimate the association between insomnia with short sleep duration and time to death. Researchers also performed a prespecified secondary analysis scoring hypertension and diabetes as potential mediators of an association between sleep variables and mortality. In addition, investigators stratified models by sex and examined insomnia with self-reported sleep duration. In secondary models, researchers used insomnia with self-reported duration as a secondary exposure.
Among 4,994 participants included in the study, researchers observed 1,163 deaths, of which 355 resulted from cardiovascular disease. The mean age of participants was 64. Participants with insomnia were more likely to be female, to smoke, and to use antidepressants, compared with those without insomnia.
Dr. Bertisch and colleagues also found that participants with short sleep duration had a 14% higher risk of mortality, compared with people without insomnia and with normal sleep duration. Insomnia with short sleep duration, however, was not associated with a higher risk of all-cause mortality. In the additional analysis, the researchers found no evidence that hypertension or diabetes mediated the association between sleep duration and mortality. Results also did not differ by sex, said Dr. Bertisch.
Limitations of this study include the fact that objective sleep duration was determined by a single night of polysomnography, and that researchers did not capture the duration of insomnia symptoms.
“Further work is needed to identify the mechanistic pathways by which insomnia with objective short sleep duration may confer increased risk for cardiovascular disease,” Dr. Bertisch concluded.