Long-Term Mortality and Incidence of Renal Dialysis and Transplantation in Type 1 Diabetes Mellitus

Abstract

We investigated long-term mortality and requirement of renal replacement therapy (RRT) in type 1 diabetes mellitus (T1DM) to study risk factors and late complication incidence of T1DM in a prospective cohort study at Lainz Hospital, Vienna, Austria. In 1983-1984, T1DM patients [n = 648; 47% females, 53% males; age, 30 +/- 11 yr; T1DM duration, 15 +/- 9 yr; body mass index, 24 +/- 4 kg/m(2); glycated hemoglobin (HbA1c), 7.6 +/- 1.6%] were stratified into HbA1c quartiles [1st, 5.9 +/- 0.5% (range, 4.2-6.5%); 2nd, 6.9 +/- 0.3% (6.6-7.4%); 3rd, 7.9 +/- 0.3% (7.5-8.4%); and 4th, 9.6 +/- 1.3% (8.5-14.8%)]. Twenty years later, both endpoints (death and RRT) were investigated by record linkage with national registries. At baseline, creatinine clearance, blood pressure, and body mass index were comparable among the HbA1c quartiles, whereas albuminuria was more frequent in the 4th quartile (+15%; P < 0.03). After the 20-yr follow-up, 13.0% of the patients had died [rate, 708 per 100,000 person-years (95% confidence interval, 557-859)], and 5.6% had received RRT [311 per 100,000 person-years (95% confidence interval, 210-412)]. Patients with the highest HbA1c values (4th quartile) had a higher mortality rate and a greater incidence of RRT (P < 0.04). In the Cox proportional hazards analysis, age, male gender, increased HbA1c, albuminuria, and reduced creatinine clearance were predictors of mortality (P < 0.05). Predictors of RRT were albuminuria (P < 0.001), reduced creatinine clearance (P < 0.001), and belonging to the 4th HbA1c quartile (P = 0.06). In Kaplan-Meier analysis, mortality was linearly associated with poor glycemia, whereas RRT incidence appeared to rise at a HbA1c threshold of approximately 8.5%. In the Lainz T1DM cohort, 13.0% mortality and 5.6% RRT were directly associated with and more frequently found in poor glycemia, showing that good glycemic control is essential for the longevity and quality of life in T1DM.