Joint associations of abdominal and general obesity and smoking with bladder cancer risk among postmenopausal women in South Korea

The independent and joint associations of waist circumference (WC), body mass index (BMI) and smoking with bladder cancer risk in postmenopausal women are unclear. A nationwide cohort study in South Korea investigated these associations. The study included 1,336,829 postmenopausal women without prior cancer from the national health screening program in 2009 who were followed until 2022. Abdominal obesity was defined as WC ≥ 85 cm and general obesity as BMI ≥ 25 kg/m² according to the Korean criteria. Over a median follow-up of 12.4 years, 2315 incident bladder cancer cases were identified. Smoking, as compared with never smoking, was independently associated with increased risk of bladder cancer (HR 1.83; 95% CI 1.53-2.19). Among participants who never smoked, abodminal obesity (HR 1.17; 95% CI1.07-1.28) and general obesity (1.09; 1.005-1.19) were associated with increased bladder cancer risk. In joint-effect analyses, individuals who ever smoked and had obesity exhibited the highest risk compared with individuals who never smoked without obesity (abdominal HR 2.27; 95% CI 1.71-3.01; general 2.36; 1.81-3.09).The authors conclude that both abdominal and general obesity were associated with higher bladder cancer risk in postmenopausal women, with substantially greater risk among those with concurrent smoking exposure.