Objective: The purpose of this study was to examine the association between sleep and subjective quality of life in an elderly Japanese population.
Methods: Elderly people aged 70 years or more (n=1,769) were selected randomly from all areas of Japan. They were visited and interviewed in November 2003. Subjective well-being of the subjects was assessed using the Philadelphia Geriatric Center (PGC) Morale Scale. A logistic regression analysis was performed using sleep-related factors as explanatory variables.
Results: A positive linear association was observed between subjective sleep sufficiency and the mean PGC Morale Scale score. The crude and adjusted odds ratios for sleep disorders such as difficulty initiating sleep, excessive daytime sleepiness, and restless legs syndrome were significantly low. The mean score was highest for a sleep duration of 7-8h and became lower at sleep durations of <6 and 9h (inverted U-shaped association). However, the adjusted odds ratio for sleep duration did not show a significant reduction.
Conclusions: In order to improve the subjective well-being of the elderly, better subjective sleep sufficiency and alleviation of sleep disorders are necessary. Different mechanisms may reduce subjective well-being in individuals who sleep less than 6h or who sleep 9h or more.