Optimum HbA1c level yet to be determined…
HbA1c is strongly related to the development of diabetes complications, but it is still controversial as to which HbA1c level to strive for in the treatment of type 1 diabetes. Swedish researchers evaluated HbA1c, followed from diagnosis, as a predictor of severe microvascular complications and to formulate HbA1c target levels for treatment.
The researchers used a longitudinal observation study following an unselected population of 451 patients diagnosed with type 1 diabetes during 1983–1987 before the age of 35 years in a region of Southeast Sweden. Retinopathy was evaluated by fundus photography and nephropathy data collected from medical records. HbA1c was measured starting from diagnosis and during the whole follow-up period of 20–24 years. Long-term weighted mean HbA1c was then calculated. Complications were analyzed in relation to HbA1c levels.
The incidence of proliferative retinopathy and persistent macroalbuminuria increased sharply and occurred earlier with increasing long-term mean HbA1c. None of the 451 patients developed proliferative retinopathy or persistent macroalbuminuria below long-term weighted mean HbA1c 7.6% (60 mmol/mol); 51% of the patients with long-term mean HbA1c above 9.5% (80 mmol/mol) developed proliferative retinopathy and 23% persistent macroalbuminuria.
The researchers concluded, “Long-term weighted mean HbA1c, measured from diagnosis, is closely associated with the development of severe complications in type 1 diabetes. Keeping HbA1c below 7.6% (60 mmol/mol) as a treatment target seems to prevent proliferative retinopathy and persistent macroalbuminuria for up to 20 years.”
- HbA1C should be < 7.6% to minimize microvascular complications.
- More studies are necessary to provide stronger evidence of this study result.
Nordwall M, Abrahamsson M, Dhir M, et al. Impact of HbA1C, Followed From Onset of Type 1 Diabetes, on the Development of Severe Retinopathy and Nephropathy: The VISS Study (Vascular Diabetic Complications in Southeast Sweden). Diabetes Care. 2015; 38:308-315