Clinical Relevance of Ultrasound-based Intramuscular Fat Infiltration Assessment in Hospitalized Older Adults (FATUS-OLD)

Sarcopenia in older adults is associated not only with loss of muscle mass but also with deterioration of muscle quality, particularly intramuscular fat infiltration. While muscle mass is commonly assessed, muscle quality remains insufficiently explored in routine clinical practice. The FATUS-OLD study aims to evaluate the clinical relevance of a novel ultrasound-based multiparametric approach to assess intramuscular fat infiltration and muscle volume in hospitalized older adults undergoing rehabilitation. The main hypothesis is that higher intramuscular fat infiltration at baseline is associated with poorer recovery of physical performance at 6 months, independently of muscle volume. This non-invasive, rapid, and radiation-free imaging approach could improve sarcopenia phenotyping and help identify new prognostic biomarkers for clinical follow-up and future interventional trials.

Inclusion Criteria: * Age ≥ 75 years * Hospitalized in rehabilitation day-hospital program * Written informed consent Exclusion Criteria: * Moderate to severe neurocognitive disorders * Inability to comply with study procedures