Body Size and Bladder Cancer Risk: A Pooled Analysis of Prospective Studies From the National Cancer Institute Cohort Consortium

PURPOSE Body size is an established risk factor for several cancers, but associations with bladder cancer risk remain unclear. METHODS We pooled data from 2,533,008 participants in 30 international cohort studies to assess associations of BMI, waist circumference, and height with bladder cancer risk. Multivariable Cox regression models, including smoking status, duration, and other confounders, were run separately by cohort and sex, and results combined by random-effects meta-analysis. RESULTS Incident first primary bladder cancer was diagnosed in 15,259 males and 5,188 females. For males, overweight (BMI, 25.0-29.9 kg/m 2 ) and obesity (BMI, ≥30 kg/m 2 ) were associated with increased risk of bladder cancer, with hazard ratios (HRs) of 1.08 (95% CI, 1.04 to 1.12) and 1.16 (95% CI, 1.10 to 1.22), respectively, when compared with normal weight (BMI, 18.5-24.9 kg/m 2 ). The corresponding HR for females were 1.02 (95% CI, 0.95 to 1.09) and 1.04 (95% CI, 0.95 to 1.14), respectively. The HR per 5 kg/m 2 increment was 1.07 (95% CI, 1.05 to 1.09) for males and 1.00 (95% CI, 0.97 to 1.04) for females. Higher waist circumference was also associated with increased risk of bladder cancer for males (HR per 10 cm increase 1.06 [95% CI, 1.03 to 1.08]) but not females (HR, 1.01 [95% CI, 0.97 to 1.04]). Results for height were largely consistent with those for BMI and waist circumference, with strong and consistent evidence for males, but not females. CONCLUSION Larger body size is associated with increased risk of bladder cancer for males, but not females. Public health interventions to prevent overweight and obesity, along with smoking cessation and reduced occupational exposure to bladder carcinogens, are likely to reduce bladder cancer incidence worldwide.