Incident Type 2 Diabetes Among Individuals With CKD: Findings From the Chronic Renal Insufficiency Cohort (CRIC) Study

Rationale & Objective: Few studies have examined incident type 2 diabetes mellitus (T2DM) in chronic kidney disease (CKD). Our objective was to examine rates of and risk factors for T2DM in CKD, using several alternative measures of glycemic control. Study Design: Prospective cohort study. Setting & Participants: 1,713 participants with reduced glomerular filtration rates and without diabetes at baseline, enrolled in the Chronic Renal Insufficiency Cohort (CRIC) Study. Predictors: Measures of kidney function and damage, fasting blood glucose, hemoglobin A_1c (HbA_1c), HOMA-IR (homeostatic model assessment of insulin resistance), demographics, family history of diabetes mellitus (DM), smoking status, medication use, systolic blood pressure, triglyceride level, high-density lipoprotein cholesterol level, body mass index, and physical activity. Outcome: Incident T2DM (defined as fasting blood glucose ≥ 126 mg/dL or prescription of insulin or oral hypoglycemic agents). Analytical Approach: Concordance between fasting blood glucose and HbA_1c levels was assessed using κ. Cause-specific hazards modeling, treating death and end-stage kidney disease as competing events, was used to predict incident T2DM. Results: Overall T2DM incidence rate was 17.81 cases/1,000 person-years. Concordance between fasting blood glucose and HbA_1c levels was low (κ for categorical versions of fasting blood glucose and HbA_1c = 13%). Unadjusted associations of measures of kidney function and damage with incident T2DM were nonsignificant (P ≥ 0.4). In multivariable models, T2DM was significantly associated with fasting blood glucose level (P = 0.002) and family history of DM (P = 0.03). The adjusted association of HOMA-IR with T2DM was comparable to that of fasting blood glucose level; the association of HbA_1c level was nonsignificant (P ≥ 0.1). Harrell's C for the models ranged from 0.62 to 0.68. Limitations: Limited number of outcome events; predictors limited to measures taken at baseline. Conclusions: The T2DM incidence rate among individuals with CKD is markedly higher than in the general population, supporting the need for greater vigilance in this population. Measures of glycemic control and family history of DM were independently associated with incident T2DM.