Are there any glycemic thresholds for the serious microvascular diabetic complications?

Abstract

We randomized 102 patients with insulin-dependent diabetes to intensified treatment (n = 48 at baseline, n = 42 after 7.5 years) or standard treatment (n = 54 at baseline, n = 47 after 7.5 years). As has previously been reported, intensified treatment resulted in a retardation of retinopathy, nephropathy, and neuropathy. For the purpose of the present study, all patients were analyzed, and the complications related to the mean glycosylated hemoglobin (HbA1c) level. Patients with mild retinopathy at onset did not develop serious retinopathy, visual deterioration, or manifest nephropathy if their mean HbA1c during 7.5 years was below 7% (normal range, 3.9%-5.7%). Neuropathy only rarely developed in patients with HbA1c below 7%. Visual acuity in the patient group with more advanced retinopathy at baseline was also better preserved if the patient had lower HbA1c; also whereas these patients needed photocoagulation treatment just as often as the patients with higher HbA1c because of proliferative retinopathy or sight-threatening macular edema. The risk for the development of serious and disabling microvascular complications seems to be small in patients with insulin-dependent diabetes mellitus if they start intensified treatment when they have mild retinopathy, and achieve mean HbA1c levels below 7% (1.2 times the upper normal limit).