Objectively measured sleep and physical function: Associations in low-income older adults with disabilities

Objective: Late-life sleep health has been tied to physical function, but little is known about these associations among socially disadvantaged populations. Design: We determined cross-sectional associations of sleep with physical function in low-income, predominantly Black older adults with disabilities. Participants: One hundred thirty-six older adults (mean age 76.0 years, 83.8% women, 82.4% Black). Measurements: Primary predictors were actigraphic total sleep time (TST), wake after sleep onset (WASO), and subjective sleep complaints. Outcomes were objective physical performance (Short Physical Performance Battery (SPPB)) and participant-reported difficulties in basic and instrumental activities of daily living (ADLs and IADLs). Results: In regression models adjusted for potential confounders, both longer TST and greater WASO were associated with lower SPPB scores and increased IADL difficulty. Participants with a mean TST in the longest (>7.5 hours) vs. intermediate (6.3-7.5 hours) tertile had 27% higher odds of additional IADL difficulty (incident rate ratio = 1.27, 95% confidence interval [CI] 1.03, 1.58). Each additional 10 minutes of WASO was associated with 0.13 point lower SPPB scores (B = −0.13, 95% CI −0.25, −0.01) and increased IADL difficulty (B = 0.02, 95% CI 0.0003, 0.04). Sex moderated the associations of WASO with IADL and ADL difficulties: associations were stronger for males. Subjective sleep complaints were not statistically significantly associated with function. Conclusions: Among disabled, low-income, mostly Black older adults, objective measures of long sleep and greater WASO are associated with poorer physical function. Effect sizes for the associations were modest; however, findings may have important implications given the significant consequences of decreased function on quality of life and caregiving demands.