Unraveling physical performance over time in hospitalized older patients with walking limitation: the role of ultrasound-derived vastus lateralis muscle thickness.

Acute hospitalization is a critical stressor that often leads to functional decline in older patients, highlighting the need for simple markers to identify at-risk individuals. Ultrasound is a feasible bedside tool for muscle mass assessment and has been proposed as a marker of physical function, but its prognostic value remains unclear. This study aimed to explore the association between ultrasound-derived muscle thickness (US-MT) and physical performance over time-gait speed (GS) and 30-s sit-to-stand (30s STS)-and selected clinical outcomes. In this prospective cohort study conducted in a geriatric department, adults aged ≥ 65 years with admission-related walking limitations were assessed at admission, discharge, 1 month, and 3 months. US-MT of the vastus lateralis was assessed at admission using ultrasonography. Longitudinal associations between US-MT and GS and 30s STS were examined using mixed-effects models. Associations with length of hospital stay (LOS), 3-month falls incidence, and 3-month mortality were examined using regression models. Among 243 participants, GS and 30s STS increased from admission to follow-up. Greater admission US-MT was modestly associated with faster GS in women (0.037 m/s; 95% CI 0.022-0.051) and with better 30s STS performance across sexes (IRR 1.24; 95% CI 1.00-1.53) across all time points. US-MT was not associated with trajectories of physical performance or with LOS, falls, or mortality. These findings suggest that admission US-MT may provide complementary bedside information on physical performance level, rather than serving as a standalone marker of recovery or clinical prognosis. ClinicalTrials.gov: NCT05798169.