HbA1c less than 7% recommended in type 1 diabetes to avoid retinopathy, nephropathy
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Study results published in Diabetes Care highlight the importance of maintaining HbA1c lower than 7% to avoid proliferative diabetic retinopathy and macroalbuminuria for people with type 1 diabetes.
“Our study determines accurately the levels of long-term sugar that can avoid complications,” Hans J. Arnqvist, MD, PhD, professor in the department of endocrinology and the department of biomedical and clinical sciences at Linköping University, Sweden, said in a related press release. “This knowledge can increase a person’s motivation to keep their blood sugar level under control.”
The Vascular Diabetic Complications in Southeast Sweden study, a population-based observational study, included 447 people with type 1 diabetes younger than 35 years who were diagnosed from 1983 to 1987 in southeast Sweden. Participants were followed from type 1 diabetes diagnosis until January 2019. Researchers estimated long-term weighted mean HbA1c and categorized complications related to HbA1c.
At 32 years of follow-up, 64% of participants had nonproliferative diabetic retinopathy, 27% had proliferative diabetic retinopathy, 9% had no retinopathy, 83% had microalbuminuria, 9% had microalbuminuria and 8% had macroalbuminuria. Those with near normal HbA1c did not have retinopathy or macroalbuminuria.
The lowest HbA1c level that was associated with proliferative diabetic retinopathy was 7.3%. The lowest HbA1c associated with macroalbuminuria was 8.1%. Proliferative diabetic retinopathy and macroalbuminuria prevalence increased as HbA1c increased, and 74% of those with proliferative diabetic retinopathy and 44% with macroalbuminuria had a weighted HbA1c of more than 9.5%.
Prevalence of both complications increased at 32 years of follow-up and occurred at lower weighted HbA1c levels compared with an analysis of data from the study at 20 to 24 years of follow-up. Retinopathy prevalence increased from 14% in the earlier analysis to 27% and nephropathy prevalence increased from 4% to 8%.
“The results of our study show that people with type 1 diabetes for at least 32 years should keep their mean long-term sugar level below 53 mmol/mol (7%), if they are to completely avoid serious damage. The risk of eye and kidney complications increases as the level increases,” Arnqvist said in the release. “Our conclusions relate to avoiding complications arising from blood vessel damage. But if a patient has problems with low blood sugar, hypoglycemia, it’s not possible to control the blood sugar level so strictly.”
Reference:
- Recommended blood sugar levels to avoid diabetes-related damage. Published Sept. 12, 2022. Accessed Sept. 19, 2022.
Perspective
Back to TopArnqvist and colleagues address what they describe as uncertainty regarding "how tight" glycemic control should be to prevent or reduce diabetic microangiopathy, citing variable HbA1c guidelines "among diabetes organizations." In fact, there is remarkable agreement among diabetes organizations regarding the consensus HbA1c goals of therapy, including the three organizations cited by the authors with the International Society for Pediatric and Adolescent Diabetes and the American Diabetes Association recommending a goal of less than 7% and the National Institute for Health and Care Excellence a goal of up to 6.5%.
The authors analyzed the 32-year follow-up results of an inception cohort (n = 447) which has been followed since diabetes onset between 1983 and 1987 in the VISS study. By way of comparison, more than 1,000 of the original 1,441 participants with type 1 diabetes in the DCCT (1983-93), the clinical trial that originally established the less than 7% HbA1c target (the UKPDS established the same HbA1c goal for type 2 diabetes), have been followed since 1993 in the observational EDIC follow-up study. The original DCCT cohort had to have diabetes for at least 1 year and had a mean duration of diabetes of 2.6 years in the primary prevention cohort and 8.7 years in the secondary intervention cohort at the time of enrollment. The less than 7% goal recommended by the DCCT was predicated on the level of glycemia achieved in the intensive treatment group that substantially reduced microvascular complications and was balanced by a relatively low risk of severe hypoglycemia compared with even lower HbA1c values. Subsequent observational follow-up during EDIC established the longer-term benefits of intensive therapy and lower HbA1c on advanced complications and cardiovascular complications.
The VISS study, using HbA1c levels and diabetes complications collected clinically, has now confirmed the desirability of keeping HbA1c levels below 7%, demonstrating the lowest long-term risk for complications. The treatment goal stated by the DCCT remains compelling: to maintain "glycemic status as close to the normal range as safely possible." The ability to achieve HbA1c levels even lower than about 7%, with substantially lower risk of hypoglycemia using current day technolog, should further lower the residual risks of developing long-term complications.
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