Prognosis of persons with type 1 diabetes on intensified insulin therapy in relation to nephropathy

Objective. To study the prognosis of persons with type 1 diabetes in relation to the degree of nephropathy at initiation of intensified insulin therapy. Design. Ten years follow-up of a cohort of 3674 patients who had participated in a 5-day group treatment and teaching programme for intensification of insulin therapy between September 1978 and December 1994. Setting. Ten diabetes centres in Germany. Subjects. A total of 3674 patients (insulin treatment before age 31), age at baseline 27 +/- 10 years, with a diabetes duration of 11 +/- 9 years. Patients were divided into three groups according to baseline renal parameters (group I, normal proteinuria, n = 1829; group II, microproteinuria, n = 1257; group III, at least macroproteinuria, n = 367). Main outcome measures. End-stage diabetic complications (blindness, amputations, renal replacement therapy), standardized mortality ratios (SMR) and causes of death. Results. Outcome measures were documented for 97% of patients; 251 (7%) had died. During follow-up, 1% of patients in group I, 4% in group II, and 47% in group III had at least one end-stage diabetic complication. SMR for men: nephropathy group I, 2.2 (95% CI = 1.5-3); group II, 3.2 (2.3-4.3); group III, 11.5 (8.8-14.7). SMR for women: group I, 2.5 (1.5-3.8); group II, 3.5 (2.2-5.3), group III, 27 (19.8-35.9). Causes of death for men and women combined: group I (total 58 deaths) - cardiovascular, 21 (36%); hypoglycaemia, 1; ketoacidosis, 3; violent deaths, 17 (29%); others, 16; group II (66 deaths) - cardiovascular, 25 (38%); hypoglycaemia, 2; ketoacidosis, 2; violent deaths, 14 (21%); others, 23; group III (114 deaths) - cardiovascular, 68 (60%); hypoglycaemia, 2; ketoacidosis, 5; infections, 15 (13%); violent deaths, 5 (4%); others, 19. Conclusions. Patients with microproteinuria have only a slightly worse prognosis than patients with normal proteinuria during the first 10 years after initiation of intensified insulin therapy. Excess mortality amongst patients who started intensified insulin therapy is mainly due to those with manifest clinical nephropathy.