Previous studies had found a link, leading to the withdrawal of pioglitazone in France and Germany. However in a bid to overcome the limitations of the previous studies the authors measured the effect of exposure to pioglitazone on bladder cancer risk across several cohorts. No evidence was seen of a link between pioglitazone or rosiglitazone and bladder cancer in men or women after adjustment for confounders. “Our large international analysis does not support a causal effect of pioglitazone on bladder cancer, thus contradicting previous studies deemed to have proven this relationship. “To fully resolve this controversy, future analyses are needed, involving longer follow-up of exposed persons and using methods to minimise allocation bias,” the researchers wrote in Diabetologia.