Muscle mass, not fat mass, predicts vertebral fracture risk: Vietnam osteoporosis study.

Vertebral fractures were diagnosed in 12.6% of the study population.

• 173 out of 1,372 participants were diagnosed with vertebral fractures.
• The study included Vietnamese adults aged ≥50 years from the Vietnam Osteoporosis Study.
• Vertebral fractures were identified via thoracolumbar radiographs using Genant's semiquantitative method.
• Participants with fractures were older (63.4 ± 9.6 vs 58.8 ± 7.3 years; p < 0.001) and more often male (38.7% vs 29.4%; p = 0.017).

Both LBMI and ASMI showed U-shaped associations with vertebral fracture risk, with higher odds at the extremes of muscle mass.

• For ASMI, the lowest quartile had increased odds of fracture (OR 1.72; 95% CI 1.02–2.95) compared to a reference quartile.
• For ASMI, the highest quartile also had increased odds of fracture (OR 2.59; 95% CI 1.36–5.02).
• Lean body mass index (LBMI) showed a similar U-shaped pattern.
• Restricted cubic splines were used to confirm and visualize the nonlinear (U-shaped) relationships.
• Adjusted logistic regression models were used to assess these associations.

Body fat mass index (BFMI) was not significantly associated with vertebral fracture risk.

• The association between BFMI and fracture risk was not statistically significant (p = 0.365).
• BFMI was derived from dual-energy X-ray absorptiometry measurements.
• This finding contrasts with the significant associations observed for muscle mass indices.

Higher trunk lean percentage was consistently associated with vertebral fracture risk across multiple quartiles.

• Odds ratios for trunk lean percentage ranged from 1.82 to 2.54 across all non-reference quartiles.
• This consistent association across non-reference quartiles distinguished trunk lean percentage from total body and leg lean percentages.
• The association was assessed using adjusted logistic regression models.

Total body lean percentage and leg lean percentage were associated with increased fracture risk only in the highest quartile.

• The highest quartile of total body lean percentage had OR 2.18 (95% CI 1.07–4.45).
• The highest quartile of leg lean percentage had OR 2.06 (95% CI 1.03–4.12).
• Lower quartiles of these percentage-based indices were not significantly associated with fracture risk.

The study used dual-energy X-ray absorptiometry to derive multiple body composition indices in a cross-sectional design.

• Indices derived included lean body mass index (LBMI), appendicular skeletal muscle mass index (ASMI), body fat mass index (BFMI), and percentage-based indices.
• The cross-sectional study included 1,372 Vietnamese adults aged ≥50 years.
• Participants were drawn from the Vietnam Osteoporosis Study.
• Both adjusted logistic regression models and restricted cubic splines were used to assess associations and explore nonlinear relationships.