Sex-specific associations between muscle-fat ratio and bone density in middle-aged adults.

Although the clinical importance of osteoporosis in middle-aged populations is widely recognized, the intricate relationships between body composition parameters, especially osteosarcopenic obesity, and bone health remain incompletely understood. This study aims to characterize the association between the skeletal muscle mass-to-visceral adipose tissue area ratio (SVR) and bone mineral density (BMD), while systematically evaluating potential variations by sex and menopausal status. Utilizing data from the National Health and Nutrition Examination Survey (2011-2018), we analyzed a cohort of 4,349 middle-aged adults (ages 40-59) with complete datasets on skeletal muscle mass (SMM), visceral adipose tissue area (VATA), and lumbar BMD. Dual-Energy X-ray Absorptiometry was employed for precise body composition analysis. Multivariate regression models were applied to analyze the relationships between SVR and BMD, with stratified analyses conducted to evaluate potential effect modifications by sex and menopausal status. Our findings revealed a significant positive correlation between SMM and BMD (β = 12.8, 95% CI: 11.2 to 14.4), while VATA exhibited an inverse relationship (β = -0.5, 95% CI: -0.6 to -0.4). Notably, men demonstrated a positive association between SVR and BMD (β = 342.4, 95% CI: 271.4 to 413.5), whereas premenopausal women displayed a non-linear, inverted U-shaped relationship between SVR and BMD, with a critical threshold identified at 0.31 kg/cm². This cross-sectional study highlights the association between SVR and lumbar BMD in middle-aged adults, revealing significant sex-specific differences. In men, higher SVR correlates with higher BMD, while in premenopausal women, BMD appears optimal when SVR falls within a specific range.