Summary

Thiazolidinediones are a relatively new class of oral drugs for diabetes. A new study confirms what was previously suspected, which is that they significantly increase the risk of bone fracture. Therefore, the management of diabetes must take this issue into account.

Introduction

Falls and fractures are to be avoided at all costs because they are linked to disability, loss of independence and even loss of life. Patients with type 2 diabetes have increased bone density and one might expect their risk of fracture to be correspondingly lower. In fact, the opposite is true. This might be a complication of diabetes or it could be related to the use of anti-diabetic medication.

While insulin is the mainstay of treatment for diabetes, there has been increasing use of a group of oral diabetic drugs called the thiazolidinediones in recent years. These improve insulin sensitivity and two examples of drugs in this class, pioglitazone and rosiglitazone, account for 21 percent of all oral antidiabetic drug prescriptions in the United States. However, there is some evidence that the thiazolidinediones might have an adverse effect upon bone health. For instance, there were more fractures in diabetic women on rosiglitazone compared to those on metformin, a different type of oral drug, in one study. The use of the thiazolidinediones is becoming more common so a team of researchers from Basel, Switzerland, and the United States, compared thiazolidinedione use in a group with, and without, bone fracture to establish the magnitude of the risk.

What was done

The researchers based their study on the United Kingdom General Practice Research Database which covers five million patients and has data on their medical records and prescriptions. From this, the researchers selected a group of nearly 67,000 patients with diabetes of whom over 50,000 had received a thiazolidinedione prescription between 1994 and 2005. From this group, all those who had had a diagnosis of a fracture in the back, hip, wrist, elbow or ribs were identified. Then a detailed analysis was done on 1020 fracture patients and 3728 matched controls.

What was found

The use rosiglitazone or pioglitazone increased the risk of fracture by two to three times compared to the rate of fracture among controls. The risk was not related to the patient's sex or age, but it did increase with the duration of thiazolidinedione usage. The risk of hip and wrist fractures from thiazolidinedione use was the most significant.

What this study means

Previous studies have shown that the thiazolidinediones are linked to reduced bone formation and accelerated bone loss. This study shows the clinical impact of this effect in terms of an increased fracture risk. The prescription of thiazolidinediones is set to increase as rates of diabetes rise. It is therefore timely that a risk associated with them is brought to the attention of doctors and patients with diabetes.