Associations of Skeletal Muscle Mass and Percent Body Fat with Balance, Gait, and Locomotive Syndrome Risk in Community-dwelling Older Women

Objectives: Locomotive syndrome (LS) is prevalent among older adults, particularly women, and is a major contributor to the need for long-term care. In rapidly aging Japan, addressing LS has become a public health priority. Although skeletal muscle mass, percent body fat (PBF), balance, and walking speed have each been linked to LS, their interrelationships remain unclear. This study examined how muscle mass and PBF are associated with LS risk in relation to balance and walking speed. Methods: This cross-sectional study analyzed community-dwelling older women aged 65 years or older, recruited from a larger cohort of adults aged 18 years or older who were able to ambulate independently. Assessments included skeletal muscle index (SMI), PBF, balance (single-leg standing time), walking speed, and LS status (two-step test, stand-up test, and the 25-question Geriatric Locomotive Function Scale). Path analysis was performed to examine the associations among variables. Results: A total of 285 participants were included. The path model demonstrated acceptable fit (goodness-of-fit index = 0.986; adjusted goodness-of-fit index = 0.945; root mean square error of approximation = 0.056). PBF was associated with balance function (β = -0.24), which was statistically related to both walking speed (β = 0.33) and LS risk (β = -0.37). SMI showed no association with balance. Conclusions: In predominantly non-sarcopenic older women, higher PBF was associated with increased LS risk, with these associations statistically related to balance and gait functions. Prospective studies are warranted to confirm these pathways and clarify causal relationships.