Factors associated with actual skeletal muscle mass increase during hip fracture rehabilitation of persons aged 80 and older

Abstract

Objectives: This study aimed to evaluate actual skeletal muscle mass change and factors associated with its increase in patients aged ≥80 years undergoing hip fracture rehabilitation.

Methods: This case-control study was conducted in the rehabilitation hospital. Participants were 368 patients aged ≥80 years undergoing hip fracture rehabilitation. Patients were divided into two groups based on the change of skeletal muscle mass index (SMI) during hospitalization: two groups with increased SMI and without increased SMI, after evaluation of skeletal muscle mass changes. Analysis between two groups and multivariate logistic regression analysis were performed to evaluate the factors associated with SMI increases.

Results: The SMI at discharge was significantly increased (5.20 kg/m²) compared to baseline (5.00 kg/m²; p <0.001). The significant differences were observed in SMI on admission, length of hospital stay, duration of exercise therapy and BMI gain between two groups. Multiple logistic regression analysis showed that hospital stay and period of exercise therapy were significantly associated with increased SMI (OR: 1.020, and 1.010 respectively; and 95% CIs: 1.010-1.030, and 1.000-1.030, respectively). Moreover, BMI and SMI on admission, and BMI gain were significantly associated with increased SMI.

Conclusions: We demonstrated that old patients with hip fractures achieved significantly increased skeletal muscle mass during rehabilitation and that BMI and SMI on admission, BMI gain, length of hospital stay, and duration of exercise therapy were factors independently associated with increased SMI. Even older patients should take exercise to acquire skeletal muscle, rather than refraining from exercising due to old age or hip fractures.

Keywords: Aged; Frail elderly; Length of stay; Protein; Sarcopenia.