Association between body composition and bone mineral density in community-dwelling older adults from Chile: a sex-stratified DXA-based cross-sectional study

Introduction. Decreased bone mineral density (BMD) remains one of the main determinants of frailty and fracture risk in older adults. Lean mass is an important contributor to bone health through mechanical loading and muscle–bone interactions. Nevertheless, evidence from Latin America remains limited, particularly DXA-based studies incorporating sex-stratified analyses. This study aimed to examine the association between body composition—emphasising lean mass—and BMD in community-dwelling older adults from Chile. Methods. A cross-sectional observational study was conducted in 274 community-dwelling adults aged ≥ 65 years from Puerto Montt, Chile (80% women). Anthropometric variables were collected, and body composition (total lean mass, total fat mass, and regional fat distribution) was assessed using dual-energy X-ray absorptiometry (DXA). BMD was analysed at the whole-body level and, in subsamples with complete data, at the femoral neck and lumbar spine (L3–L4). Spearman correlation analyses and multiple linear regression models adjusted for age, body mass index (BMI), sex, and regional fat distribution were performed. Results. In participants with complete whole-body BMD data (n = 203), total lean mass was strongly and positively associated with whole-body BMD (ρ = 0.66; p < 0.001), with a stronger correlation in men (ρ = 0.62) than in women (ρ = 0.47). In regression models, lean mass was the primary statistical determinant of whole-body BMD, explaining 53.4% of the variance (adjusted R² = 0.534). Adding sex and regional fat distribution modestly improved model performance (adjusted R² ≈ 0.56). In contrast, adiposity measures showed weaker and site-dependent associations with BMD. Conclusions. Lean mass is the primary statistical determinant of whole-body BMD in older Chilean adults, with relevant sex-related differences. These findings support strategies to preserve muscle mass as a central component of osteoporosis prevention and healthy musculoskeletal ageing, particularly in Latin American settings.