Type 1 diabetes: HbA1c levels above 6.9% associated with complications, finds BMJ study

Sweden: Researchers from Sweden have identified a window of HbA_1c levels that can control complications in people with type 1 diabetes.

According to the study, maintaining HbA_1c levels between 48 and 52 mmol/mol (6.5% and 6.9%) reduce the risk of diabetes complications in people with type 1 diabetes, according to a recent study.

The study, published in the BMJ journal, found that risk of nephropathy and retinopathy did not differ at HbA_1c levels <6.5% but increased for severe hypoglycemia (low blood sugar) compared with HbA_1c levels 6.5-6.9%.

The risk for severe complications mainly occurred at HbA_1c levels >8.6%, but for milder complications was increased at HbA_1c levels >7.0%.

According to Mayo Clinic, type 1 diabetes, once known as juvenile diabetes or insulin-dependent diabetes, is a chronic condition in which the pancreas produces little or no insulin. Insulin is a hormone needed to allow sugar (glucose) to enter cells to produce energy.

Multiple studies have confirmed that a higher HbA_1c level is an independent risk factor for diabetes complications. But still, there exists no concrete evidence for the association between the two in type 1 diabetes patients.

Marcus Lind, University of Gothenburg, Gothenburg, Sweden, and colleagues evaluated if the lowest target level for glycated haemoglobin (HbA_1c) of <6.5% is associated with a lower risk for retinopathy and nephropathy than less tight control in children and adults with type 1 diabetes.

For the purpose, the researchers used data from the Swedish Diabetes Registry which included over 10,000 adults and children with type 1 diabetes. The researchers grouped the participants into five categories depending on their HbA1c levels.

The lowest HbA1c category was for participants with HbA1c levels of below 48 mmol/mol (6.5%). The highest HbA1c category was for those with an HbA1c of greater than 71 mmol/mol (8.6%). The team reviewed risk of complications including retinopathy, nephropathy (kidney disease) and episodes of severe hypoglycemia.

Key findings of the study include:

• Retinopathy and nephropathy were more likely in people with an HbA1c of 53 mmol/mol (7%) and above.


• More severe forms of these complications, proliferative retinopathy and chronic kidney disease, were more likely in people with an HbA1c level above 71 mmol/mol (8.6%).


• People with an HbA1c of below 53 mmol/mol (6.5%) had an increased risk of experiencing severe hypoglycemia.

"We found no difference in risk of retinopathy and nephropathy at HbA_1c levels <6.5% (<48 mmol/mol) but an increased risk of severe hypoglycaemia compared with levels of 6.5-6.9% (48-52 mmol/mol). Severe complications mainly occurred at HbA_1c levels >8.6% (>70 mmol/mol), whereas the risk of milder complications increased at HbA_1c levels >7.0% (>53 mmol/mol). In people with HbA_1c levels <6.5% (<48 mmol/mol), clinicians should focus on avoidance of frequent hypoglycaemia and obtaining a good diabetes-related quality of life, or else increase the target level to 6.5-6.9% (48-52 mmol/mol)," wrote the authors.

"Other measures, including time in range, time in hypoglycaemia, and variation in glycaemia will be essential complementary measures to HbA_1c in clinical practice and future studies," they concluded.

More Information: "HbA_1c level as a risk factor for retinopathy and nephropathy in children and adults with type 1 diabetes: Swedish population-based cohort study" published in the BMJ journal.

DOI: https://doi.org/10.1136/bmj.l4894

Journal Information: British Medical Journal