Changes in nocturnal sleep and daytime nap durations predict all-cause mortality among older adults: the Panel on Health and Ageing of Singaporean Elderly

• Published in: Sleep (New York, N.Y.) N.Y.), 2018-07, Vol.41 (7), p.1
• Main Authors: Cheng, Grand H-L, Malhotra, Rahul, Østbye, Truls, Chan, Angelique, Ma, Stefan, Lo, June C
• Format: Article
• Language: English
• Subjects: Aged; Aging; Analysis; Causes of; Circadian Rhythm; Elderly; Female; Health aspects; Health risk assessment; Humans; Independent Living; Longitudinal Studies; Male; Middle Aged; Mortality; Older people; Proportional Hazards Models; Regression analysis; Singapore; Sleep; Social networks; Time Factors
• ISSN: 0161-8105; 1550-9109
• DOI: 10.1093/sleep/zsy087

To determine the effects of changes in nocturnal sleep and daytime nap durations on all-cause mortality among older adults. Two-thousand four-hundred forty-eight community-dwelling older Singaporeans (≥60 years) reported their nocturnal sleep and daytime nap durations at baseline (2009) and the 2-year follow-up. At each phase, they were grouped into the recommended (7-8 hours), short (≤6 hours), and long (≥9 hours) sleep duration categories, and the none (0 hour), short (≤1 hour), and long (>1 hour) nap duration categories. Cox regression analysis was conducted to quantify the associations of changes in sleep and nap durations over 2 years with all-cause mortality risk in the subsequent 4 years (till end of 2015). Multivariable fractional polynomial regression, which treated sleep and nap durations as continuous variables was conducted as a supplementary analysis. Relative to individuals who had the recommended sleep durations at both baseline and follow-up, the risks of all-cause mortality were higher among older adults who reported considerable changes in sleep duration (from short to long sleep and vice versa, hazard ratio [HR] = 2.14-2.56). Furthermore, compared to those who did not nap at both time points, significantly higher mortality risks were found in individuals who showed any increase in nap duration (HR = 1.86-2.16), or reduced their nap from long to short duration (HR = 1.86). Supplementary analysis revealed similar findings. In addition to the change in nocturnal sleep duration, change in daytime nap duration can also predict risks of all-cause mortality among older adults. It is crucial to track older adults' sleep and nap durations longitudinally.