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.

引言：多项队列研究持续显示，肥胖与胆结石风险增加之间存在显著关联。然而，单独的体重指数（BMI）可能无法完全涵盖肥胖的复杂性。本研究旨在通过竞争风险模型分析不同肥胖指标与胆结石发病率之间的关联。
方法：分析了英国生物银行（UK Biobank）基线时无胆结石的459,523名参与者。采用Cox比例风险模型、竞争风险模型及限制性立方样条（restricted cubic spline, RCS），评估了除体重指数（BMI）外的11项肥胖指标（包括体型指数（a body shape index, ABSI）、体脂指数（body adiposity index, BAI）、身体圆润度指数（body roundness index, BRI）、圆锥指数（conicity index, ConI）、心脏代谢指数（cardiometabolic index, CMI）、臀围（hip circumference, HC）、内脏脂肪指数（visceral adiposity index, VAI）、脂质蓄积产物（lipid accumulation product, LAP）、腰围（waist circumference, WC）、腰高比（waist-to-height ratio, WHtR）及腰臀比（waist-to-hip ratio, WHR））与胆结石发生风险之间的纵向关联。
结果：在12.54年的随访期内，共有14,951名参与者患上胆结石。调整混杂因素后，竞争风险回归分析显示，BMI、BRI、BAI、CI、CMI、HC、LAP、VAI、WC及WHtR均与胆结石风险增加呈正相关。ABSI与WHR则与胆结石发病率呈“J型”关联，提示存在非线性关系。敏感性分析证实，即使排除随访1年内发生胆结石的参与者，结果仍保持一致。
结论：肥胖的不同维度均与胆结石风险增加显著相关。这些发现强调了管理肥胖（包括整体体重及腹部脂肪）对预防胆结石发生的重要性。