Abstract
A growing body of evidence has established a close association between obesity and bone metabolism. The body roundness index (BRI), a novel anthropometric parameter, has demonstrated superior predictive capability for estimating both visceral fat percentage and total body fat percentage when compared with traditional measures such as Body Mass Index (BMI) and waist circumference. However, there is a paucity of research exploring the relationship between BRI and bone mineral density (BMD). Therefore, this investigation was designed to assess the association between BRI and lumbar spine BMD among adults in the United States. Data were obtained from the National Health and Nutrition Examination Survey (NHANES) cycles spanning 2011 to 2018, including participants aged 20 years and older. To evaluate the linear association between BRI and lumbar BMD, weighted multivariable regression models were applied. Additionally, weighted smooth curve fitting along with a 2-piecewise linear regression approach was utilized to detect potential nonlinear relationships. Stratified subgroup analyses were carried out based on age, sex, race/ethnicity, and BMI categories. The final analysis included a total of 10,996 adult participants. In the fully adjusted regression model, BRI exhibited a significant inverse association with lumbar BMD (β = -0.048; 95% CI: -0.059 to -0.037). This negative correlation persisted across most subgroups (all interaction P-value > .05), with the exception of BMI-defined strata. A nonlinear association between BRI and lumbar BMD was identified, with an inflection point observed at a BRI value of 7.63. Comparable nonlinear patterns were detected in subpopulations stratified by age (<40 years and ≥ 40 years), gender (male), and race/ethnicity (non-Hispanic White and other race). This study highlights a significant inverse and nonlinear relationship between the BRI and lumbar spine BMD in U.S. adults. These findings may offer novel insights for the development of targeted strategies in osteoporosis prevention and intervention.