Nephropathy is delayed by intensified insulin treatment in patients with insulin-dependent diabetes mellitus and retinopathy.

Patients with insulin-dependent diabetes mellitus (IDDM) and non-proliferative retinopathy were randomized to intensified conventional insulin treatment (ICT, n = 44) or regular treatment (RT, n = 51). During a 3-year period the glycosylated haemoglobin (HbA1c) levels were reduced to a greater extent (P = 0.00001) in the ICT group (from 9.5 +/- 0.2 to 7.4%, P = 0.0001) than in the RT group (9.4 +/- 0.2 to 9.0 +/- 0.2, P = 0.004). The urinary albumin excretion rate (UAER) increased significantly (P = 0.033) in the RT group but not in the ICT group, and the UAER differed significantly (P = 0.031) between the groups after 3 years. The mean HbA1c values during the study period independently influenced the deterioration of UAER levels (P = 0.029). Initial diastolic blood pressure (P = 0.112), the HbA1c value at entry (P = 0.480) and the smoking habits (P = 0.959) were not related to change of UAER levels. Manifest nephropathy after 3 years was seen almost exclusively in patients with HbA1c levels above 9%. Improved blood glucose control, without 'near normoglycaemia', delayed the progression of nephropathy in patients with IDDM and retinopathy.