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Elevated A1C Linked to Fractures in Diabetes

Feb 9, 2019
 

Author: Steve Freed, R.PH., CDE


Researchers find increased risk in people with type 1 who have glucose levels greater than 8.0%.

In a new study, researchers identified a key factor specific to type 1 diabetes (T1D).  The study reports that in patients who have type 1 diabetes, elevated A1C levels significantly increase the risk of a fall from standing height or less that results in a broken bone.

Glucose levels appear to play a role in the known risk of fracture in diabetes; however, the effect is only significant in type 1 diabetes, according to the studies, suggesting insulin deficiency and elevated A1C levels earlier in life could take a toll on bone mass among these patients.

The study investigated the association between the A1Cs and fracture risk by using a large cohort of people newly diagnosed with type 1 and type 2 diabetes.  Both types of diabetes are associated with fragility fractures. The results showed that elevated A1C levels are associated with an increased risk of fracture in people with type 1 diabetes.

The overall greater fracture risk in diabetes has been well documented, with an important study showing the risk of hip fracture, in particular, is increased two- to threefold in people who have type 2 diabetes compared to the general population, and by as much as sixfold in the less-common type 1 diabetes.

In the study, published online January 19 in the Endocrine Society’s Journal of Clinical Endocrinology & Metabolism, the authors identified 3,329 people with type 1 diabetes, including 672 people with a recorded low-trauma fragility fracture after diagnosis, and 44,275 people with type 2 diabetes, including 8m859 cases of fracture. What was unusual about the study was that it focused on a 3-year average of hemoglobin A1c values instead of short-term measurements. Participants had an average of nine A1c measurements if they had T1D and 11 if they had T2D.

An A1c level about 8%, which is considered poor glycemic management, is associated with an increased risk of fractures in people with T1D but not T2D, at least in short-term disease.

The authors suggest that the risk of fracture in people with T2D might be because of factors beyond glycemic management, such as comorbidities or medication. “Nevertheless, fracture risk in type 2 diabetes is of clinical relevance as well as it is a major health concern worldwide due to its high prevalence,” according to the authors.

The study, which included researchers from Boston University School of Medicine in Lexington, Massachusetts, focused on people whose T1D or T2D was newly diagnosed between 1995 and 2015. Results indicate that median duration between diabetes onset and fracture date was 4.5 years for both types of diabetes.

The risk of a fragility fracture — defined as any fall from standing height or lower that resulted in a broken bone — was increased in people with type 1 diabetes who had a mean HbA1c > 8.0% compared to people with type 1 diabetes and “good” glucose management (mean HbA1c ≤ 7.0%) (adjusted odds ratio [OR], 1.39).

In people with type 1 diabetes, certain comorbidities related to vascular complications were also associated with an increased risk of fracture, such as diabetic retinopathy (OR, 1.29) and chronic renal failure (OR, 2.24). There was no significant relationship between glycemic management and fracture rates in type 2 diabetes.

In both diabetes groups, the first fragility fracture occurred relatively early in the disease course, within a mean 4.5 years of diabetes diagnosis. Overall, the people with type people with type 1 diabetes who had a mean HbA1c of 8.7%.  Higher A1Cs with a much earlier onset of type 1 diabetes, typically in youth, may increase fracture risk in those people because of the interaction of insulin and bone, considering that as much as 50% to 60% of peak bone mass is accrued during puberty, the authors speculate.

Researchers report that the risk of fracture was increased in people with T1D who have a mean HbA1c >8.0% (aOR 1.39, 95% CI, 1.06-1.83) compared with people with T1D who have a mean HbA1c value less than 7%. While no such effect was detected in people with T2D, their risk of fracture also was elevated, most notably with current use of rosiglitazone and pioglitazone.

Practice Pearls:

  • In both diabetes groups, the first fragility fracture occurred relatively early in the disease course, within a mean 4.5 years of diabetes diagnosis.
  • The risk of a fragility fracture — defined as any fall from standing height or lower that resulted in a broken bone — was increased in people with type 1 diabetes who had a mean HbA1c > 8.0%
  • Fracture risk in type 2 diabetes is of clinical relevance as well, as it is a major health concern worldwide due to its high prevalence.

J Clin Endocrinol Metab. Published online January 16, 2019. Abstract