Association of objectively measured sleep with frailty and 5-year mortality in community-dwelling older adults

Study Objectives: To determine whether actigraphy-measured sleep was independently associated with risk of frailty and mortality over a 5-year period among older adults. Methods: We used data from Waves 2 (W2) and 3 (W3) (2010-2015) of the National Social Life, Health and Aging Project, a prospective cohort of community-dwelling older adults born between 1920 and 1947. One-third of W2 respondents were randomly selected to participate in a sleep study, of whom N = 727 consented and N = 615 were included in the analytic sample. Participants were instructed to wear a wrist actigraph for 72 h (2.93 0.01 nights). Actigraphic sleep parameters were averaged across nights and included total sleep time, percent sleep, sleep fragmentation index, and wake after sleep onset. Subjective sleep was collected via questionnaire. Frailty was assessed using modified Fried Frailty Index. Vital status was ascertained at the time of the W3 interview. W3 frailty/mortality status was analyzed jointly with a four-level variable: robust, pre-frail, frail, and deceased. Associations were modeled per 10-unit increase. Results: After controlling for baseline frailty (robust and pre-frail categories), age, sex, education, body mass index, and sleep time preference, a higher sleep fragmentation index was associated with frailty (OR = 1.70, 95% CI: 1.02-2.84) and mortality (OR = 2.12, 95% CI: 1.09-4.09). Greater wake after sleep onset (OR = 1.24, 95% CI: 1.02-1.50) and lower percent sleep (OR = 0.41, 95% CI: 0.17-0.97) were associated with mortality. Conclusions: Among community-dwelling older adults, actigraphic sleep is associated with frailty and all-cause mortality over a 5-year period. Further investigation is warranted to elucidate the physiological mechanisms underlying these associations.