Associations between accelerometry-measured physical activity, sleep, and mobility improvement in hospitalised older adults

Introduction:

Mobility decline during hospitalisation is common among older adults and is associated with adverse outcomes including prolonged length of stay, institutionalisation, and mortality. While physical activity and sleep are key modifiable factors influencing recovery and mobility improvement, their relationships remain underexplored in acute geriatric settings.

Methods:

We conducted a prospective observational pilot study involving 15 hospitalised older adults (mean age 84.9 years) admitted to an acute geriatric ward. Participants wore wrist- and thigh-worn ActiGraph wGT3X-BT accelerometers continuously during admission to measure sleep parameters and physical activity. Mobility was assessed at baseline and discharge using the de Morton Mobility Index (DEMMI). Accelerometry-derived metrics included daily time spent in light, moderate, and vigorous physical activity, moderate-to-vigorous physical activity (MVPA) as a percentage of waking hours, and sleep fragmentation indices (number of awakenings, sleep efficiency). Descriptive analyses and Mann-Whitney U tests were conducted to examine relationships between activity, sleep, and mobility changes.

Results:

DEMMI scores improved significantly (mean change +6.8 points, 95% CI: –13.4 to –0.2, p=0.045). Participants spent a median of 63 minutes/day in light activity and 2.4 minutes/day in moderate activity. Median MVPA comprised 0.25% of waking hours. Sleep was fragmented (mean 18 awakenings/night; sleep efficiency 69%). Among participants with improved mobility (n=6), the mean number of nocturnal awakenings was 14.2 (SD=2.1) compared to 17.4 (SD=2.4) in those with stable or worsened mobility (n=5), though not statistically significant (p=0.114). Sleep efficiency was 76.4% (SD=19.9) in the improved group versus 80.1% (SD=3.7) in the stable/worsened group (p=0.680).

Conclusions:

Despite low physical activity levels and fragmented sleep, mobility improved significantly during admission. Although participants with mobility improvement showed fewer nocturnal awakenings, differences were not statistically significant. Larger studies are needed to clarify these associations and to inform interventions targeting sleep and activity to optimise mobility outcomes in hospitalised older adults.