Poor glycemic control associated with fracture in type 1 but not type 2 diabetes

Patients with type 1 diabetes and poor glycemic control may have a higher risk for low-trauma fracture, but the same association is not seen in patients with type 2 diabetes, a recent study found.

Researchers performed a nested case-control study using a U.K. database to examine the association between level of glycemic control and risk for low-trauma fracture in patients with diabetes. Patients whose type 1 or type 2 diabetes was newly diagnosed between 1995 and 2015 and who had a low-trauma fracture after diabetes onset were matched with four controls by age, sex, general practice, fracture date, and type and duration of diabetes. The researchers analyzed initial HbA1c level, mean HbA1c level in the three years before the index date, and the last HbA1c level before the index date and used conditional logistic regression to assess the association between HbA1c level and low-trauma fracture risk, adjusting for several covariates. Results were published Jan. 16 by the Journal of Clinical Endocrinology & Metabolism.

A total of 3,329 patients with type 1 diabetes (672 with fracture and 2,657 matched controls) and 44,275 patients with type 2 diabetes (8,859 with fracture and 35,416 matched controls) were included in the study. The median time between diabetes onset and fracture was 4.5 years for both type 1 and type 2 diabetes. Patients with type 1 diabetes and a mean three-year HbA1c level greater than 8.0% had a higher fracture risk (adjusted odds ratio, 1.39; 95% CI, 1.06 to 1.83) than those with a mean three-year HbA1c level of 7.0% or less. This effect was not seen in patients with type 2 diabetes, although a higher fracture risk was noted in those currently taking rosiglitazone and pioglitazone in this group, independent of glycemic control.

The authors noted that the patients with type 2 diabetes in their study had good glycemic control, that residual confounding may have affected their analysis, and that type of fracture was usually unknown, among other limitations. They concluded that the impact of glycemic control on fracture risk varies by type of diabetes. “While poor glycemic control elevated the risk of fracture in [type 1 diabetes patients], we observed no such association in patients with [type 2 diabetes],” the authors wrote. “This might be attributed to a protective effect of insulin resistance in early disease.”