Association between sleep duration and activity of daily living in the elderly aged 65 years and older in China

Abstract

Objective: To investigate the association between sleep duration and activity of daily living (ADL) in the elderly aged 65 years and older in China. Methods: A total of 11 247 subjects aged 65 and above were included in the Chinese Elderly Health Factors Tracking Survey from March 29, 2005 to April 8, 2019. Self-made questionnaire was used to collect the data of population sociological characteristics, health status and disease status. ADL status was assessed by basic activities of daily living. The association between sleep duration and ADL impairment was assessed by Cox proportional risk regression model. The dose-response relationship between sleep duration and ADL impairment was analyzed using restricted cubic spline function. Results: The age of the subjects was (79±10) years, including 5 793(51.5%) females. The incidence of ADL impairment was 33.3% (3 747/11 247). Subjects were divided into short, medium, and long sleep groups according to sleep duration of fewer than seven hours, seven to eight hours, or more than eight hours. The number of short, medium and long sleepers was 2 974 (26.4%), 4 922 (43.8%) and 3 351(29.8%), respectively. The intermediate sleep group had the lowest incidence of impaired ADL (4.98/100 person-years). Cox proportional risk regression model analysis showed that: taking the intermediate sleep group as reference, after adjustment of gender, age, marital status, educational level, place of residence, living with family, smoking, drinking, exercise, frequency of fruit consumption, vegetable intake frequency, sleep quality, factors such as hypertension, diabetes, heart disease and cerebrovascular disease, the long sleep time increased the risk of impaired ADL [HR (95%CI): 1.148 (1.062-1.241)]. Subgroup analysis showed a weak positive multiplicative interaction between sleep duration and age [HR (95%CI): 1.004 (1.000-1.009)], but no multiplicative interaction between sleep duration and sex [HR(95%CI): 0.948 (0.870-1.034)]. Longer sleep duration increased the risk of ADL impairment in women [HR (95%CI): 1.195 (1.074-1.329)], but not in men [HR (95%CI): 1.084 (0.966-1.217)]. Longer sleep duration increased the risk of ADL impairment in people aged 80 years and older [HR (95%CI): 1.185 (1.076-1.305)], but not in people younger than 80 years [HR (95%CI): 1.020 (0.890-1.169)]. There was a non-linear dose-response relationship between sleep duration and ADL damage (P=0.007), and the risk of ADL damage was lowest when sleep duration was 7.5 h. Conclusion: Sleep duration was positively correlated with the risk of ADL impairment in the elderly in a nonlinear dose-response relationship.