Day-to-day sleep efficiency and driving behaviors in older adults with and without cognitive impairment.

Sleep disturbances are common in older adults, particularly those with cognitive impairment. This study examines how day-to-day sleep quality impacts real-world driving behaviors, offering insight into sleep as a potential functional biomarker of cognitive health. We monitored 149 community-dwelling older adults (90 cognitively impaired, 59 unimpaired) over 12 weeks. Sleep was measured via wrist-worn actigraphy, and driving data were collected via an in-vehicle sensor system. A zero-inflated Poisson regression model examined whether sleep efficiency was associated with next-day driving likelihood and frequency, and whether these relationships varied by cognitive status. Better sleep efficiency increased the likelihood of driving the next day more for cognitively impaired participants than for unimpaired participants. Higher sleep efficiency was associated with increased driving frequency in both groups. These findings underscore the importance of daily sleep variability as a potential digital biomarker for functional abilities in older adults, highlighting opportunities for early intervention to preserve mobility and independence. A 1 standard deviation increase in sleep efficiency increases next-day trip counts (incidence rate ratio = 1.014).In cognitively impaired participants, better sleep lowers the odds of not driving the next day (odds ratio = 0.877).Among those who choose to drive, trip counts do not differ by cognitive status.