Purpose: The purpose of this systematic review and meta-analysis was to evaluate the potential associations between anthropometric characteristics and bladder cancer risk, synthesizing longitudinal cohort studies.
Methods: Literature search across MEDLINE, EMBASE, Scopus, Google Scholar and Cochrane Central was performed up to December 31, 2019 and data abstraction was performed independently by two authors. Random-effects (DerSimonian-Laird) models were used to estimate pooled relative risks (RR) and 95% confidence intervals (95%CI); subgroup analyses were performed in geographical region, mean age, publication year, length of follow-up, sample size, method of body mass index (BMI) estimation and adjustment for smoking.
Results: 27 studies were included (88 593 bladder cancer cases in a total cohort of 49 647 098 subjects). Increased bladder cancer risk was noted in overweight men (pooled RR=1.12, 95%CI: 1.04-1.21) but not in overweight women. Both obese men (pooled RR=1.14, 95%CI: 1.06-1.22) and women (pooled RR=1.19, 95%CI: 1.02-1.38) showed increased risk. Interestingly, height increase per 5 cm did not seem to affect risk of bladder cancer in men (pooled RR=1.03, 95%CI: 0.99- 1.06) and women (pooled RR=1.02, 95%CI: 0.97-1.06). Larger waist circumference was associated with bladder cancer risk in men (pooled RR=1.18, 95%CI: 1.09-1.26) but not women.
Conclusion: Bladder cancer risk seems to be related with obesity overall and central obesity in men. In contrast to other cancer types, height does not seem to affect risk, but more studies are needed to extract safe conclusions.