Aim: The present study examined the association between objective measures of sleep quality and performance-based measures of physical function in community-dwelling oldest old Japanese.
Methods: This cross-sectional study included 207 community-dwelling adults aged 80 years or older (92 men, 115 women; age 83.5 ± 2.6 years [range 80-95 years]). Participants wore an accelerometer (ActiGraph GT3X+) on their non-dominant wrist for 24 h per day over seven consecutive nights. Sleep parameters included total sleep time, sleep efficiency and wake after sleep onset during the night for a week. Performance-based physical function measures were handgrip strength, knee extension strength, and usual and maximum walking speeds. Multivariable linear regression was carried out to determine the associations between weekly sleep parameter averages and physical function measures.
Results: Approximately 24% of participants had a total sleep time of less than 6 h a night, and 13% had greater than 8 h a night. Overall, average daily physical activity was 1771.8 ± 520.6 (counts/min/day). In multiple linear regression, sleep efficiency and wake after sleep onset were significantly associated with maximum walking speed (β = 0.277; 95% confidence interval [CI] 0.103 to 0.351 and β = -0.214; 95% CI -0.339 to -0.082, respectively) and usual walking speed (β = 0.200, 95% CI 0.035 to 0.305 and β = -0.174; 95% CI -0.341 to -0.064, respectively), after adjusting for potential confounding factors including daily physical activity. Both sleep qualities were also independently associated with knee extension strength. However, wake after sleep onset was not associated with handgrip strength.
Conclusion: Objectively measured sleep quality was associated with physical function in the oldest old. Further research is required to identify the temporality of associations between sleep and physical function.
Keywords: accelerometer; oldest old; physical activity; physical function; sleep.
© 2014 Japan Geriatrics Society.