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, particularly from DXA-based studies incorporating sex-stratified analyses, remains limited. This study aimed to examine the association between body composition-emphasizing lean mass-and BMD in community-dwelling older adults from Chile. METHODS: A cross-sectional study was conducted in 274 community-dwelling adults aged ≥ 65 years from Puerto Montt, Chile (80% women). Anthropometric data were collected, and body composition (total lean mass, total fat mass, and regional fat distribution) was assessed via dual-energy X-ray absorptiometry (DXA). BMD was analyzed 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 = 274), total lean mass was moderately 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 the multivariable regression models, lean mass showed the strongest independent association with whole-body BMD, explaining 53.4% of the variance in Model 1 (adjusted R² = 0.534). The inclusion of sex and regional fat distribution modestly improved model performance (adjusted R² ≈ 0.56). Analyses of lumbar spine (L3-L4) and femoral neck BMD were conducted in smaller subsamples with available regional DXA data (n = 133 for each site), in which associations with body composition variables were generally weaker or nonsignificant. Adiposity measurements revealed weaker and site-dependent associations with BMD. CONCLUSIONS: Lean mass showed the strongest independent association with whole-body BMD in community-dwelling older Chilean adults, with modest differences between women and men. These findings support the relevance of lean mass as an important correlate of bone health during aging and provide evidence from a Latin American population.