Study objectives: This study examined the association between disturbed sleep and poorer daytime function in older women.
Design: Observational study.
Participants: 2,889 women, mean age 83.5 years, participating in the 2002-2004 examination of the Study of Osteoporotic Fractures.
Measurements and results: Participants wore actigraphs for an average +/- SD of 4.1 +/- 0.83 24-hour periods. Actigraphy measured sleep variables were total sleep time and hours awake after sleep onset during the night and daytime napping behavior. Neuromuscular performance measurements included gait speed, chair stands, and grip strength. Functional limitations were assessed as self-reported difficulty with one or more of 6 instrumental activities of daily living (IADL). In fully adjusted, multivariable models, women who slept <6 hours per night walked 3.5% slower than those who slept 6.0-6.8 hours. Those who slept > or =7.5 hours took 4.1% longer to complete 5 chair stands than those who slept 6.8-7.5 hours. With higher wake after sleep onset (> or =1.6 hours compared to <0.7 hours) gait speed was 9.1% slower; it took 7.6% longer to complete 5 chair stands, and odds of functional limitation were 1.8 (95% CI: 1.4, 2.4) higher. Women with 1.0-1.8 hours of daytime sleep had higher odds (1.4 [95% CI: 1.1, 1.8]) of a functional limitation than those with <0.5 hours. Sleep variables did not appear to be associated with grip strength.
Conclusions: Objectively measured poorer sleep was associated with worse physical function. Future research is needed to identify the underlying mechanisms for the association between poor sleep and functional decline.