Association Between Objectively Measured Sleep Quality and Physical Function in the Oldest Old

Background: Physical function is an important factor for health and well-being of older adults. Performance-based measures of physical function have been related to an elevated risk of frailty, disability, and mortality. Poor sleep quality has been associated with reduced physical function in older adults. However, little is known about the association between objective measures of sleep and physical functioning in the oldest old.

Purpose: This study examines the association between objective measures of sleep quality and physical function in community-dwelling Japanese adults aged 80 or older.

Methods: Participants (100 males and 123 females, 83.5 ± 2.8 years old [range 80 to 95]) wore an accelerometer (ActiGraph GT3X+) on their non-dominant wrist for 24 hours per day for 7 consecutive days. Sleep parameters included total sleep time, sleep efficiency, sleep latency, and wake after sleep onset (WASO) during the night for a week. Performance-based physical function measures were grip strength, knee extension strength, usual walking speed, and maximum walking speed. Multivariable linear regression was used to determine the associations between average of weekly sleep parameters and physical function measures.

Results: : In this study, 25.6% of the participants had total sleep time less than 6 hours and 13.9% had total sleep time greater than 8 hours a night. In partial correlations controlled for age and sex, all physical function measures were significantly associated with sleep efficiency (r = 0.17 to 0.27, p < 0.05 for all) and WASO (r = -0.14 to -0.24, p < 0.05 for all). After adjustment for potential confounding factors including daily physical activity, physical function was significantly associated with both sleep efficiency (β = 0.235, p = 0.017) and WASO (β = -0.053, p = 0.022). Usual walking speed was independently associated with sleep efficiency (β = 0.010, p=0.018) and WASO (β = -0.003, p = 0.012). Knee extension strength was not associated with any sleep parameters (p > 0.05).

Conclusions: Objectively measured poor sleep quality was associated with poor physical function. A better nighttime sleep quality might help improve physical functioning in the oldest old. Further research is needed to identify the temporality of the association between poor sleep and physical function.