Sleep Inertia, Daytime Sleepiness, and Falls in Older Adults of The Wisconsin Sleep Cohort

Abstract Study Objectives Examine associations between sleep inertia, daytime sleepiness, and falls in older adults of the Wisconsin Sleep Cohort (WSC). Materials and methods Cross-sectional data from WSC participants were used. Participants completed the Sleep Inertia Questionnaire (SIQ) and Epworth Sleepiness Scale (ESS). Elevated sleep inertia (ESI) was defined as the upper quartile (SIQ > 37), while ESS > 10 defined excessive daytime sleepiness (EDS). Falls outcomes included self-reported recurrent (<2 vs. 2+) and injurious (no vs. yes) falls over the previous year. Logistic regressions examined associations with falls outcomes. Fully adjusted analyses included demographics and outcome-specific sleep, psychiatric, medical, physical, and cognitive covariates. Secondary analyses explored associations with SIQ subscales. Results The recurrent falls sample included 392 older adults (74.5 ± 6.6 years; 44.9% female), while 162 participants with ≥1 fall comprised the injurious falls sample (75.4 ± 6.6 years; 45.1% female). In unadjusted analyses, higher SIQ scores and ESI were significantly associated with recurrent and injurious falls; however, in fully adjusted analyses, the associations remained significant only for recurrent falls (SIQ: OR = 1.04, 95% CI = 1.00–1.07; ESI: OR = 2.00, 95% CI = 1.07–3.73). Higher ESS scores and EDS were significantly associated with recurrent falls in unadjusted analyses, but not in fully adjusted analyses. Neither ESS nor EDS was associated with injurious falls. In SIQ subscale analyses, Physiological symptoms were most strongly associated with recurrent falls, whereas Cognitive symptoms were most strongly associated with injurious falls. Conclusions Sleep inertia may represent an important, under-recognized risk factor for falls in older adults.