Effects of Metabolic Factors, Race-Ethnicity, and Sex on the Development of Nephropathy in Adolescents and Young Adults With Type 2 Diabetes: Results From the TODAY Study

OBJECTIVE To describe the longitudinal effects of sex, race-ethnicity, and metabolic factors on the risk of developing diabetic kidney disease (DKD) in the Treatment Options for Type 2 Diabetes in Adolescents and Youth (TODAY) cohort. RESEARCH DESIGN AND METHODS Urine albumin-to-creatinine ratio (UACR) and estimated glomerular filtration rate (eGFR) by serum creatinine and cystatin C were assessed annually for up to 15 years after study entry. Markers of DKD included micro- and macroalbuminuria (UACR >= 30 mg/g and >= 300 mg/g, respectively), hyperfiltration (eGFR >= 135 min/1.73 m(2)), and rapid eGFR annual decline (>3 mL/min/1.73 m(2) and/or >= 3.3%). The relationships between risk factors and DKD were evaluated longitudinally using time-to-event models. RESULTS Data were available on 677 participants, average age at baseline 14 years, with a mean +/- SD follow-up of 10.2 +/- 4.5 years. Each 1% increment in HbA(1c) conferred higher risk of microalbuminuria (hazard ratio 1.24 [95% CI 1.18, 1.30]), macroalbuminuria (1.22, [1.11, 1.34]), hyperfiltration (1.11, [1.05, 1.17]), and rapid eGFR decline (1.12, [1.04, 1.20]). No sex or race-ethnicity differences were observed for the 14-year cumulative incidence of elevated albuminuria. Higher systolic blood pressure and baseline serum uric acid, and lower indices of beta-cell function (C-peptide index and oral disposition index [oDI]), increased the risk of microalbuminuria, while higher triglycerides increased risk of micro- and macroalbuminuria. Lower oDI levels, female sex, and Hispanic ethnicity were associated with higher risk of hyperfiltration. CONCLUSIONS Elevated HbA(1c) was a shared risk factor among all phenotypes of DKD in this longitudinal cohort of adolescents and young adults with youth-onset type 2 diabetes. Other risk factors included elevated blood pressure, triglycerides, serum uric acid, and beta-cell dysfunction.