How You Sleep May Impact How You Walk: A Pilot Cohort Study (Preprint)

BACKGROUND Higher step width variability while walking is associated with poor physical function and falls. Sleep is an established modifiable risk factor for both gait and physical function impairments, but it has yet to be examined whether sleep is also related to step width variability. OBJECTIVE This study aimed to evaluate the cross-sectional associations between objectively measured sleep quality, using cardiopulmonary coupling (CPC) spectrograms, and step width variability during a preferred walking condition among middle aged and older adults. METHODS This study included 72 adults (mean age: 71 years, 51% female, 90% non-Hispanic White) who had ≥ 2 nights of objectively measured sleep (CPC via SleepImage ring) and completed a 10-meter walk while at preferred speed wearing inertial sensors (APDM Mobility Lab). Sleep measures included: sleep duration, efficiency, fragmentation, stability, apnea hypopnea index, time SpO2 levels < 90%, oxygen desaturation index, and respiratory disturbance index. Additional derived sleep variables were explored using LASSO models. Step width variability was defined by asymmetry of lateral step variability and categorized as medial (≤ -7.5 cm), minimal (within ± 7.5 cm; reference), or lateral displacement (≥ 7.5 cm). Multinomial logistic regression models adjusted for age, sex, race, education, and body mass index evaluated cross-sectional associations between sleep and step width variability categories. RESULTS We found that 1% higher sleep fragmentation was associated with 6% higher probability of step width variability ≥ 7.5 cm (95% CI: 1.01-1.11), while 1% higher sleep stability was associated with 5% lower probability of variability ≥ 7.5 cm (95% CI: 0.91-0.99), compared to minimal variability. From the LASSO models, we found that 1% higher sleep quality index, 1% higher REM sleep, 1-second shorter apnea duration, and 1-beat/minute slower mean heart rate were also associated with lower probability of lateral compared to minimal displacement. CONCLUSIONS Poor sleep quality was associated with higher step width variability among middle aged and older adults. This suggests that sleep may be a modifiable risk factor for maintaining postural stability while walking among middle aged and older adults. Future studies are needed to examine whether intervening on these sleep measures also lowers risk of falls.