Beyond BMI: The role of diabetes and central obesity in fracture risk-Insights from the UK biobank

Abstract

Background A higher body mass index (BMI) is associated with lower fracture risk, yet diabetes, linked to central obesity, increases this risk. This study uses the UK Biobank to investigate the interplay between general and central adiposity, diabetes, and fracture risk, focusing on waist circumference (WC) and waist-to-height ratio (WHtR).Methods This prospective cohort study included 446,219 UK Biobank participants. Individuals were categorized by BMI (normal, overweight, obese) and by tertiles of WC and WHtR. Multivariable Cox models were used to evaluate the association between these obesity measures and fracture incidence, with additional analysis stratified by diabetes status.Results Individuals with overweight or obesity had a reduced risk of fracture compared to those with normal weight (adjusted hazard ratio [aHR] 0.79, 95% confidence interval [CI] 0.76-0.82 for overweight; aHR 0.73, 95% CI 0.70-0.77 for obesity). Higher WC and WHtR were generally associated with a lower risk of fracture; however, a U-shaped pattern was observed. Among individuals with overweight or obesity, higher WC was associated with an increased risk of fracture (aHR 1.12, 95% CI 1.05-1.20 in the overweight group; aHR 1.23, 95% CI 1.12-1.35 in the obesity group). Additionally, diabetes was independently associated with a higher fracture risk across all BMI categories, with the risk further elevated in individuals with central obesity.Conclusions Although a higher BMI appears protective, central obesity and diabetes are important contributors to increased fracture risk in individuals with obesity. These findings emphasize that, beyond maintaining a healthy weight, clinicians should assess central obesity and diabetes to better identify those at high fracture risk.