Type 2 diabetes increases fracture risk to minor degree

The risk of fracture is probably only slightly increased in persons with type 2 diabetes, said Peter Vestergaard, MD, PhD, DrMedSc, from the Osteoporosis Clinic, Aarhus Amtssygehus, Denmark.

Diabetes is known to affect bone metabolism. The thiazolidinediones are associated with an increase in fracture risk, primarily in women, but in those not taking thiazolidinediones, fracture of the hip and possibly the forearm still appear to be increased, he said. The confusion comes from a higher bone mineral density (BMD) in persons with type 2 diabetes despite the increased fracture risk. This increase in BMD, however, may be a result of a higher body mass index (BMI) in those with type 2 diabetes.

In the Rotterdam study of more than 6000 men and women aged 55 years or older, subjects with type 2 diabetes and impaired glucose tolerance both had a higher BMD than those with normal glucose tolerance. However, subjects with impaired glucose tolerance had a decrease in their fracture risk, whereas those with diabetes (primarily those with already established and treated diabetes) had an increased fracture risk. The authors attributed this increase in fracture risk in type 2 diabetes to the long-term complications associated with diabetes.

In Dr. Vestergaard's own meta-analysis (Osteoporosis Int 2007;18:427-444) hip fracture risk was increased in both type 1 and type 2 diabetes compared with controls (without diabetes) but the relative increase in fracture of the hip was significantly higher in type 1 versus type 2 diabetes. BMD Z-scores were decreased in the spine and hip in persons with type 1 diabetes and increased in the spine and hip in type 2 diabetes. Again, BMI was a major determinant for BMD in both the spine and hip. "There was no relationship by glucose [on BMD]," he said.

A common factor such as complications may explain the increase in fracture risk in diabetes. Indeed, studies have shown that diabetic patients with eye disease or neuropathy have an increased risk of fractures. A higher BMI may ameliorate the increase in fracture risk in type 2 diabetes, he said. "Fracture risk is either not increased, or increased only to a minor degree, in type 2 diabetes," he concluded. Additionally, this slight increase is limited to hip fracture and possibly forearm fracture. For certain, hip fracture risk is not decreased in type 2 diabetes.