Aims: 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.
Methods: 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.
Results: 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%.
Conclusion/interpretation: 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.