Combined Use of Sleep Quality and Duration Is More Closely Associated With Mortality Risk Among Older Adults: A Population-based Kyoto-Kameoka Prospective Cohort Study

Background: Whether sleep quality and duration assessed from multiple domains, either individually or in combination, are strongly associated with mortality risk in older adults remains unelucidated. We aimed to clarify these relationships. Methods: We enrolled 7,668 older (age ≥65 years) Japanese adults in the Kyoto-Kameoka prospective cohort study who provided valid responses to the Pittsburgh Sleep Quality Index (PSQI) in a mail-in survey. Sleep quality and duration were classified into six groups using the previously validated PSQI: short sleep duration (SSD: <360 min/day)/sleep disturbance (SD: ≥5.5 PSQI points), n = 701; SSD/non-sleep disturbance (NSD: <5.5 PSQI points), n = 100; optimal sleep duration (OSD: 360–480 min/day)/NSD, n = 1,863; OSD/SD, n = 2,113; long sleep duration (LSD: >480 min/day)/NSD, n = 1,972; LSD/SD, n = 919. Mortality data were collected from February 15, 2012, to November 30, 2016. We evaluated the relationship between all-cause mortality risk and sleep quality and duration (and their combinations) using a multivariable Cox proportional hazards model that included baseline covariates. Results: The median follow-up period was 4.75 years (34,826 person-years), with a total of 616 deaths. After adjusting for confounders, compared with other groups, SSD/SD and LSD/SD had the highest hazard ratio (HR) of mortality (SSD/SD: HR 1.56; 95% confidence interval [CI], 1.10–2.19; SSD/NSD: HR 1.27; 95% CI, 0.47–3.48; OSD/NSD: reference; OSD/SD: HR 1.20; 95% CI, 0.91–1.59; LSD/NSD: HR 1.35; 95% CI, 1.03–1.77; LSD/SD: HR 1.83; 95% CI, 1.37–2.45). However, mortality risk was not associated with the interaction between sleep quality and duration. Conclusion: Older adults with sleep disturbances involving SSD and LSD have a strong positive association with mortality risk, suggesting an additive effect between sleep quality and duration.