Glycemic Control, Renal Complications, and Current Smoking in Relation to Excess Risk of Mortality in Persons With Type 1 Diabetes

BACKGROUND: A substantial excess risk of mortality still exists in persons with type 1 diabetes. The aim of this study was to evaluate the excess risk of mortality in persons with type 1 diabetes without renal complications who target goals for glycemic control and are nonsmokers. Furthermore, we evaluated risk factors of death due to hypoglycemia or ketoacidosis in young adults with type 1 diabetes. METHODS: We evaluated a cohort based on 33 915 persons with type 1 diabetes and 169 249 randomly selected controls from the general population matched on age, sex, and county followed over a mean of 8.0 and 8.3 years, respectively. Hazard ratios (HRs) for all-cause and cardiovascular disease (CVD) mortality for persons with type 1 diabetes versus controls were estimated. RESULTS: The adjusted HRs for all-cause and CVD mortality for persons with type 1 diabetes without renal complications (normoalbuminuria and eGFR ≥ 60 ml/min) and HbA1c ≤ 6.9% (52 mmol/mol) compared to controls were 1.22 (95% CI 0.98-1.52) and 1.03 (95% CI 0.66-1.60), respectively. The HRs increased with higher updated mean HbA1c. For nonsmokers in this group, the HRs for all-cause and CVD mortality were somewhat lower: 1.11 (95% CI 0.87-1.42) and 0.89 (95% CI 0.53-1.48) at updated mean HbA1c ≤ 6.9% (52 mmol/mol). HRs for significant predictors for deaths due to hypoglycemia or ketoacidosis in persons < 50 years were male sex 2.40 (95% CI 1.27-4.52), smoking 2.86 (95% CI 1.57-5.22), lower educational level 3.01 (95% CI 1.26-7.22), albuminuria or advanced kidney disease 2.83 (95% CI 1.63-4.93), earlier hospital diagnosis of hypoglycemia or ketoacidosis 2.30 (95% CI 1.20-4.42), and earlier diagnosis of intoxication 2.53 (95% CI 1.06-6.04). CONCLUSIONS: If currently recommended HbA1c targets can be reached, renal complications and smoking avoided in persons with type 1 diabetes, the excess risk of mortality will likely converge substantially to that of the general population.