Bone Mineral Density in 50+ Years of Diabetes

People with longstanding T1DM have low rates of fractures and similar bone mineral density as those without T1DM, according to a study published online in Acta Diabetologia.

The small pilot study is the first to report on bone health in people who have had T1DM for 50 years or more.

“Our results found an unexpectedly low prevalence of fractures in a large cohort of aging people with T1D duration greater than 50 years. Accordingly, we showed an unexpectedly low prevalence of osteoporosis and BMD [bone mineral density] values comparable to non-diabetic peers, as shown by normal Z-scores, in a subgroup of subjects from the same cohort,” wrote first author Ernesto Maddaloni, MD, of Harvard Medical School (Boston, MA), and colleagues.

Past studies have suggested that diabetes increases the risk of osteoporotic fractures, suggesting that bone fragility is a complication of diabetes. However, most studies of bone health in T1DM have been done in people under age 40, even though the risk of osteoporosis increases with age. 

To look at the issue in older individuals, researchers evaluated the prevalence of non-vertebral fractures in participants in the Joslin 50-Year Medalist Study, which has been following people diagnosed with T1DM for 50 years or more. The study included 985 participants with a mean age of 66 years, mean T1DM duration of 54.7 years, and mean HbA1c 7.2%. Participants self-reported fractures and cardiovascular disease on questionnaires.

In a subset of 65 participants (mean age of 62.6 years, mean diabetes duration 52.5 years, mean HbA1c 7.1%), they also measured bone mineral density (BMD) using dual-energy X-ray absorptiometry.

Normal BMD was defined according to World Health Organization (WHO) criteria for BMD T-scores: normal ≥-1.0, low or osteopenia <-1.0 and >-2.5, and osteoporosis ≤-2.5 SD.

Key Results:

• Low fracture prevalence: 1.12% overall, 0.20% hip, 0.91% wrist

• Normal BMD of spine, total hip, femoral neck, and distal radius (Z-scores: +1.15, +0.23, -0.01, +0.26, respectively)

♦ Cumulative prevalence of osteoporosis of the spine, total hip, and femoral neck was 4.6%

♦ Osteopenia prevalence at all sites: 66.2%

• Lower BMD significantly linked to higher total cholesterol (P=0.003), triglycerides (P=0.045) and LDL levels (P=0.009), but not HDL (P=0.160)

• Low BMD at the femoral neck significantly linked to CVD (prevalence risk ratio 4.6, 95% CI 1.2–18.1, P=0.03)

♦ No other diabetic vascular complication was linked to low BMD

The authors noted that Medalists in this study had BMD that was comparable or better than an age-, gender-, and race-matched population without T1DM. They also pointed out that the rates of osteoporosis were “unexpectedly low” at 4.6%, compared to 10.3% in the general US population 50 years or older. On the other hand, 66.2% of people with T1DM in this study had osteopenia, compared to 43.9% of US adults.

They also mentioned that studies in people with shorter T1DM duration have found lower BMD compared to those without diabetes, while longer term studies show similar results as the current study.  

Several explanations may account for the discrepant results, they wrote. Individuals in this study had relatively few complications and more consistent care for their diabetes, so they may have had better glycemic control, as well as improved diet and other risk factors throughout the course of their disease. Also, some studies have suggested that long-term insulin therapy may improve initial bone loss associated with T1DM.

A “strong independent” link existed between CVD and low BMD, they continued. Studies have also suggested a strong link between vascular complications and fracture rate or decreased BMD. Medalists in this study have low rates of vascular complications, the authors added, suggesting that protecting against vascular complications may help protect bone health.

“While the ‘extreme disease duration’ of this population could limit the generalizability of our results, the study of people like Medalists is necessary to study the effects of long-term T1D,” they concluded. “This extraordinary population enables us to identify patterns and factors in a growing portion of the population, which could potentially heavily burden the healthcare system. As these individuals have escaped the primary causes of early death among those with diabetes, namely CVD, this suggests an emphasis for better glycemic control and other factors which protect against vascular disease.”

Take-home Points

• A first study of bone health in people with T1DM for 50+ years shows low rates of fractures and normal bone mineral density compared to nondiabetic peers.

• There was a strong independent link between CVD and low BMD, suggesting protecting against vascular complications may also protect bone health.

• Because of the extreme duration of individuals in this study, the results may not apply to the general population with T1DM, but they provide important information on the effects of long-standing T1DM.

The authors report no conflicts of interest.

Reference: Maddaloni E, et al. Bone health in subjects with type 1 diabetes for more than 50 years. Acta Diabetol. 2017 Feb 25.