Trabecular Bone Score, HbA1c May Predict Fractures in Type 1 Diabetes

SEATTLE — Trabecular bone score (TBS) and HbA1c may be good predictors of incident fractures in patients with type 1 diabetes, although bone mineral density (BMD) may not be predictive, according to a new study presented at the American Society for Bone and Mineral Research (ASBMR) 2015 Annual Meeting. 

“Identifying patients with type 1 diabetes who are at risk for fractures is challenging because bone density measurements do not identify those patients. They are often very young and risk prediction in younger cohorts is even more difficult. So, there is an unmet need for more precise fracture risk prediction in individuals with type 1 diabetes,” lead study investigator Thomas Neumann, MD, of Jena University Hospital in Thuringia, Germany, said.

“Calculating trabecular bone score can become a new screening instrument, if we get more information on cut off values in different ages and gender.”

Dr Neumann, who presented the findings at the meeting, said studies have shown that patients with type 1 diabetes have a higher risk for fracture than those without diabetes. Nevertheless, it appears that BMD underestimates the observed fracture rate in this patient population.

This is the first prospective study to investigate which parameters may be predictive for incident fractures in patients with type 1 diabetes, according to Dr Neumann.

The researchers included 52 men and 53 women with a mean age of 43.6 years and a mean duration of diabetes of 21.8 years in the study. They followed this cohort for a median of 6.9 years and analyzed the associations of traditional risk factors for fractures, including age, gender, family history of osteoporosis, and nicotine use.

The researchers also looked at BMD at the lumbar spine, femoral neck, and total hip, as well as TBS and HbA1c.

Over the study period, BMD decreased at the lumbar spine, femoral neck, and total hip in women, according to the study results. In contrast, BMD decreased at the femoral neck only in men.

In univariate regression analysis, only female gender was associated with greater decreases in BMD at the lumbar spine and total hip.

Data indicated that at least one new fracture occurred in 18 patients (17.1%). The researchers observed no differences between those with fractures and those without in age or BMD.

However, those with fractures had higher HbA1c values (65.1 mmol/mol vs 57.9 mmol/mol; P=.043) and lower mean TBS scores (1.281 vs 1.369; P=.013) at baseline.

Additionally, the researchers found that the 10-year risk for major osteoporotic fractures and hip fractures as evaluated the Fracture Risk Assessment Tool (FRAX) did not identify patients with subsequent fractures.

In logistic regression analysis, however, receiver operating characteristic (ROC) curves showed that mean TBS score and HbA1c levels were able to discriminate patients with incident fractures from those without fractures (area under the curve [AUC]=0.72; P=.003 for combined TBS scores and HbA1c levels).

Diabetes duration and glycemic control at baseline were not associated with annual change in BMD at the lumbar spine, femoral neck, total hip, or TBS. 

Dr Neumann said this study is remarkable because it highlights the fact that fracture rates are not only high in middle-aged men and women with type 1 diabetes, but they are also not predictable with traditional parameters. He added that only HbA1c and mean TBS score are independently associated with incident fractures and that specific cut off values for TBS-based risk assessment need to be validated in further studies.

“Osteoporosis has to be regarded as a comorbidity of type 1 diabetes,” Dr Neumann told Endocrinology Advisor. “The take-home message is: look carefully at your patients with type 1 diabetes concerning fracture risk, identify traditional fracture risk factors, do not stop fracture risk assessment with a normal BMD, and most importantly, HbA1c is important, so try to lower it.”

TBS — a texture analysis of lumbar bone densitometry measurements — is being touted as a helpful parameter to estimate the risk for fracture in patients with type 1 diabetes, Dr Neumann explained.

In this study, exclusion criteria at study entry included diabetes duration less than 3 years, co-medication with corticosteroids, and menopause or no menstrual period within the last 12 months. Other exclusion criteria included pregnancy, chronic inflammatory disease, malnutrition, renal failure, severe mental disease, or somatic disease.

Reference

1. Neumann T, Keil M, Lehmann G, et al. Abstract FR0355: TBS and HbA1c but not BMD are Predictors of Incident Fractures in Type 1 Diabetes. Presented at: American Society for Bone and Mineral Research (ASBMR) 2015 Annual Meeting; Oct. 9-12, 2015; Seattle.