By David Liu, PHD

Saturday Sept 15, 2012 (foodconsumer.org) -- A new study in Canadian Medical Association Journal suggests that taking some diabetes type 2 medications can moderately increase risk of bladder cancer.

Patients with type 2 diabetes are known to have 40 percent increased risk for bladder cancer and thiazolidinediones particularly pioglitazone may raise the risk, according to the study authors.

Jeffrey A. Johnson of University of Alberta, Edmonton, Alta and colleagues  conducted the meta-analysis of data from four randomized, controlled trials, five cohort studies and one case-control study and found use of thiazolidinediones and pioglitazone was associated with increased risk bladder cancer.

For the study, Johnson et al. searched major biomedical database and identified four randomized controlled trials,  five cohort studies and one case-control study involving of a total of 2,657,365 diabetes type 2 patients of whom 3643 were diagnosed with bladder cancer.

One trial failed to associate  pioglitazone use with bladder cancer and two trials that evaluated rosiglitazone use found no association between its use and risk of bladder cancer in the diabetes type 2 patients.

But the cohort studies showed use of thiazolidinediones was linked to a 15 percent increased risk of bladder cancer whereas using pioglitazone was linked to a 22 percent increase in the risk.

The researchers explained "The limited evidence available supports the hypothesis that thiazolidinediones, particularly pioglitazone, are associated with an increased risk of bladder cancer among adults with type 2 diabetes."