Burden and Excess Risk of Adverse Outcomes in Patients With Type 1 Diabetes Using KDIGO Classification: A National Cohort Study

OBJECTIVE The widely adopted Kidney Disease: Improving Global Outcomes (KDIGO) classification system has been underused in assessing the burden and risk of adverse outcomes in type 1 diabetes. This observational study aimed to clarify how each KDIGO category correlates with outcomes, including mortality, in this patient group. RESEARCH DESIGN AND METHODS In 40,199 individuals with type 1 diabetes from the Swedish National Diabetes Register, we examined the 1) prevalence of different KDIGO categories at baseline; 2) incidence of adverse kidney and cardiovascular (CV) outcomes, including mortality, within each category; and 3) association of baseline category with excess risk of five outcomes: 40% decline in estimated glomerular filtration rate (eGFR), kidney failure, major adverse kidney/CV events, and all-cause mortality. Cox regression analyses were conducted using three different reference categories: 1) the conventional low-risk “combined G1A1 + G2A1”; 2) “G1A1” alone to assess whether G2A1 had excess risk; and 3) “G1bA1” alone to evaluate whether eGFR ≥105 mL/min/1.73 m2 had increased risk. RESULTS Among 39,067 included patients, with a mean follow-up of 9.1 years, 18.5% presented with chronic kidney disease (CKD), defined as eGFR <60 mL/min/1.73 m2 and/or albuminuria. A progressive increase in the incidence and adjusted hazard ratio for all studied outcomes was found with advancing eGFR and albuminuria categories, including in G2A1 (non-CKD). A eGFR ≥105 mL/min/1.73 m2 without albuminuria was not associated with increased risk. CONCLUSIONS A progressively increasing burden of all studied adverse outcomes was observed with advancing KDIGO categories. Even individuals with preserved eGFR and normoalbuminuria (G2A1) conventionally perceived as non-CKD, had an excess risk for all outcomes.