Metabolic Syndrome and Bladder Cancer Risk: A Meta-Analysis of Cohort Studies

BACKGROUND: This study aimed to systematically assess the relationship between metabolic syndrome (MetS) and the incidence of bladder cancer. METHODS: We performed a comprehensive search of the PubMed, EMBASE, Cochrane CENTRAL, Web of Science, and Scopus databases to retrieve eligible cohort studies. Pooled relative risk (RR) and corresponding 95% confidence interval (CI) were estimated using a random-effects model. Robustness was checked via a leave-one-out sensitivity analysis. Publication bias was assessed both graphically (funnel plots) and statistically (Begg's and Egger's tests). RESULTS: The final meta-analysis incorporated six studies, encompassing a total population of over 13 million individuals and 22,000 newly diagnosed cases. The aggregated data revealed that MetS was associated with a statistically significant 12% elevation in bladder cancer risk (RR = 1.12; 95% CI: 1.03-1.22). Sensitivity analysis demonstrated the stability of these results, and no evidence of significant publication bias was observed. Substantial heterogeneity was observed across studies (I² = 62.4%, p = 0.009). Sensitivity analysis demonstrated the robustness of the pooled estimate. Exclusion of any single study did not materially alter the overall conclusion. Begg's test produced a p-value of 0.711, while Egger's test showed a p-value of 0.062. CONCLUSIONS: MetS is linked to a moderately higher risk of developing bladder cancer. These results underscore the importance of maintaining metabolic health as a potential strategy for bladder cancer prevention.