Association of Objective Long Sleep Duration and Insomnia with Objective Short Sleep Duration Phenotypes with Mortality in Older Persons
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Objective
To investigate the association of objective long sleep duration (LS) and insomnia with objective short sleep duration (ISSD) with mortality in older persons.
Methods
In 3,054 men (average age 76.4±5.5; mean follow-up=12.1 years) and 3,048 women (average age 83.6±4.8; mean follow-up=5.4 years), Cox proportional hazards models examined the association of LS (actigraphy-estimated sleep duration>8h) and ISSD (insomnia [difficulty initiating or maintaining sleep and/or sleep medication use ≥3/week] and concurrent actigraphy-estimated sleep duration<6h) with mortality. Other phenotypes ( insomnia with normal sleep duration [INSD; insomnia and sleep duration 6-8h]; asymptomatic short sleep [AS; no insomnia and sleep duration<6h]) were also examined. Participants with normal sleep (NS; no insomnia and sleep duration 6-8h) served as the reference group. Models were adjusted for demographics and comorbidities.
Results
In unadjusted models, LS was associated with increased mortality in men and women when compared with NS. In women only, LS was associated with higher mortality after adjustment for demographics and comorbidity compared with NS (HR 1.30 [1.07, 1.59]). In demographic-adjusted models and across cohorts, ISSD was significantly associated with an increased hazard of mortality compared with NS (HR 1.25 [1.10, 1.43] for men; 1.36 [1.11, 1.67] for women). This association was not significant in either cohort after adjusting for comorbidity. Persons with INSD or AS did not have increased mortality risk compared with NS.
Conclusion
LS and ISSD are at-risk phenotypes in older persons. Associations with mortality may be mediated by chronic diseases. Future work should examine whether sleep improvements decrease mortality in older persons.
STATEMENT OF SIGNIFICANCE
Prior studies have reported inconsistent results on the association between insomnia with objective short sleep duration (ISSD) and mortality in older persons. While long sleep duration (LS) has been associated with mortality, self-reported assessments may be subject to bias. Through analysis of two large cohorts of community-dwelling older men and women with objective sleep measurements and robust longitudinal data, we found ISSD and LS to be associated with all-cause mortality. After controlling for the presence of chronic conditions, however, only LS in women was significantly associated with mortality. Our findings suggest that underlying comorbidities mediate the risk of ISSD and LS in older persons and that objective measures may be needed to differentiate risk among older persons with insomnia symptoms.
