(HealthDay News) — For patients with type 1 diabetes, long-term weighted mean hemoglobin A1c (HbA1c) is associated with development of severe microvascular complications, according to a study published online Dec. 15 in Diabetes Care.

Maria Nordwall, M.D., Ph.D., from Linköping University in Norrköping, Sweden, and colleagues conduced a longitudinal observation study involving an unselected population of 451 patients diagnosed with type 1 diabetes during 1983 to 1987, before age 35. The authors measured HbA1c from diagnosis through 20 to 24 years of follow-up, and calculated long-term weighted mean HbA1c. Complications in relation to HbA1c levels were examined.

The researchers found that increasing long-term mean HbA1c correlated with sharply increased and earlier incidence of proliferative retinopathy and persistent macroalbuminuria. Among patients with long-term weighted mean HbA1c below 7.6 percent, none developed proliferative retinopathy or persistent macroalbuminuria. Among those with long-term mean HbA1c above 9.5 percent, 51 percent developed proliferative retinopathy and 23 percent developed persistent macroalbuminuria.

“Keeping HbA1c below 7.6 percent (60 mmol/mol) as a treatment target seems to prevent proliferative retinopathy and persistent macroalbuminuria for up to 20 years,” the authors write.


  1. Nordwall, M, et al. Diabetes Care, 2014; doi:10.2337/dc14-1203