Supplementary Material for: Risk of gallstones increases with multiple dimensions of obesity indexes: a prospective study based on the UK Biobank

Introduction: Numerous cohort studies have consistently shown a significant link between obesity and an increased risk of gallstones. However, BMI alone may not fully capture the complexity of obesity. This study aimed to analyze the associations between different obesity indexes and the incidence of gallstones, using a competing risk model.
Methods: 459,523 UK Biobank participants without gallstones at baseline were analyzed. Cox proportional hazards models, competing risk models, and restricted cubic spline (RCS) were performed to assess the longitudinal associations between 11 obesity indexes including a body shape index (ABSI), body adiposity index (BAI), body roundness index (BRI), conicity index (ConI), cardiometabolic index (CMI), hip circumference(HC), visceral adiposity index (VAI), lipid accumulation product (LAP), waist circumference (WC), waist-to-height ratio (WHtR), and waist-to-hip ratio (WHR) apart from BMI and gallstone occurrence risk, respectively.
Results: Over a follow-up period of 12.54 years, a total of 14,951 participants developed gallstones. After adjusting for confounding factors, competing risk regression analyses revealed that BMI, BRI, BAI, CI, CMI, HC, LAP, VAI, WC, and WHtR were all positively associated with an increased risk of gallstones. ABSI and WHR showed a "J-shaped" association with the incidence of gallstones, suggesting a non-linear relationship. Sensitivity analyses confirmed the consistency of the results even after excluding participants who developed gallstones within one year of follow-up.
Conclusion: Different dimensions of obesity are all significantly associated with an increased risk of gallstones. These findings highlight the importance of managing obesity, including both overall body weight and abdominal fat, to prevent the occurrence of gallstones.