Regular use of diabetes drugs Avandia and Actos doubles the chances of fractures in female patients, according to a study by researchers from the University of East Anglia and Wake Forest University in North Carolina.

The drugs, prescribed in the case of type 2 diabetes, have already been linked to heart problems. They carry strong warnings on their labels in that sense.

The researchers reviewed 10 previous drug trials involving 14,000 patients and found that the drugs significantly increased the risk of fractures in women but not in men. To be more specific, for every 20 women in their 70s with type 2 diabetes who took thiazolidinediones — rosiglitgizone (brand name Avandia) and pioglitazone (brand name Actos) for at least one year, one of them has a chance of suffering a fracture. The risk is not that high in women in their 50s, use of the drugs in their case leading to one extra fracture for every 55 women.

One possible explanation for these findings is that women are affected because of an interaction between the drugs and estrogen, which weakens bones in women, according to lead researcher Dr. Yoon Loke, a clinical senior lecturer at the University of East Anglia. Also, women have smaller, thinner bones to begin with, so that even a loss of a little bone mass can increase the risk of fractures, Loke added. However, more research is needed to find out why the sexes were affected differently.

The study was published in the December 10 issue of the Canadian Medical Association Journal.