Metabolic syndrome and risk of bladder cancer: prospective cohort study in the metabolic syndrome and cancer project (Me-Can).

There are little data on the putative association between factors in the metabolic syndrome (MetS) and risk of bladder cancer. In the Metabolic Syndrome and Cancer project (Me-Can), measurements of height, weight, blood pressure and circulating levels of glucose, cholesterol, and triglycerides had been collected from 578,700 subjects in cohorts in Norway, Austria, and Sweden. We used Cox proportional hazard models to calculate relative risks (RRs) of bladder cancer by exposures divided into quintiles, in categories according to the World Health Organisation (WHO) and as a continuous standardized variable (z-score with mean = 0 and standard deviation = 1) for each separate component and its standardized sum, a composite MetS score. RRs were corrected for random error in measurements. During a mean follow-up of 11.7 years (SD = 7.6), 1,587 men and 327 women were diagnosed with bladder cancer. Significant associations with risk were found among men per one unit increment of z-score for blood pressure, RR = 1.13 (95% CI 1.03-1.25), and the composite MetS score, RR = 1.10 (95% CI 1.01-1.18). Among women, glucose was nonsignificantly associated with risk, RR = 1.41 (95% CI 0.97-2.06). No statistically significant interactions were found between the components in the MetS in relation to bladder cancer risk. Hypertension and a composite MetS score were significantly but modestly associated with an increased risk of bladder cancer among men and elevated glucose was associated with a nonsignificant increase in risk among women.