Associations between abdominal obesity and the prevalence of fractures among Chinese adults: insights from a nationwide cross-sectional study

Purpose To investigate the links between abdominal obesity and skeletal outcomes in a population-based cohort in China. Methods 8,251 participants from the COPS cohort were enrolled in this study and categorized by quartiles of abdominal obesity indices. Abdominal obesity was determined using sex-specific waist circumference (WC) cutoffs (≥ 90 cm for males, ≥ 85 cm for females), or a waist-to-height ratio (WHtR) ≥0.5. Physical performance and balance were assessed using the Five-Repetition Sit-to-Stand Test (5R-STS) and the Sharpened Romberg test. Vertebral fractures were identified by spine X-ray examination, while information on clinical fractures in recent 5y were collected by a self-report questionnaire. Multivariate regression models were employed with covariate adjustments. Predictive capacity of adiposity metrics for fractures was assessed through ROC analysis. Results Abdominal obesity was linked to lower bone turnover rate and higher BMD. However, it was also significantly associated with impaired balance, evidenced by prolonged 5R-STS times and higher rates of positive Sharpened Romberg tests. The prevalence of vertebral fractures and clinical fractures in recent 5y increased across quartiles of WC, WHtR, and Chinese visceral adiposity index (CVAI) (all p 0.001). An increment of one standard deviation (SD) in these indices was linked to a 19%–30% greater prevalence of fractures. These findings remained robust after limiting analysis to Genant grade ≥2 vertebral fractures. BMI-stratified analysis revealed that abdominal obesity independently increased the prevalence of vertebral fractures regardless of BMI. Notably, normal-weight individuals with abdominal obesity had a 1.75-fold higher prevalence of vertebral fractures ( p = 0.022), while BMI alone showed no significant effect. Moreover, WHtR demonstrated superior predictive capacity for vertebral fractures and Genant grade ≥2 vertebral fractures vs BMI (AUC 0.62 vs 0.52), with optimal performance when combined with age, sex, fracture history, and BMD (AUC = 0.80). Conclusion Abdominal obesity was independently associated with impaired balance and elevated prevalence of vertebral fractures and clinical fractures, even in normal-weight individuals. WHtR demonstrated superior discriminative power for vertebral fractures.