Abstract P171: Hemoglobin A1c and Incident Albuminuria Among Individuals Without Diabetes: The Coronary Artery Risk Development in Young Adults (CARDIA) Study

Abstract

Background: Higher hemoglobin A1c (HbA1c) has been associated with an increased risk of reduced estimated glomerular filtration rate <60 mls/min/1.73m2 among individuals without diabetes. However, it is unclear whether higher HbA1c in the non-diabetic glycemic range also is associated with an increased risk of albuminuria. This study investigated the association of HbA1c with incident albuminuria in a biracial cohort of middle-aged men and women without a history of diabetes in the Coronary Artery Risk Development in Young Adults (CARDIA) Study. Methods: The CARDIA Study is a prospective cohort study of 5,115 African-American and white adults, age 18-30 years at baseline (1985-86), from four field centers in the United States: Birmingham, AL; Chicago, IL; Minneapolis, MN; and Oakland, CA. Participants with prevalent diabetes (defined as fasting glucose ≥126 mg/dL, 2-hour post-challenge glucose ≥ 200 mg/dL, HbA1c ≥ 6.5%, or used diabetes medications) or albuminuria (defined as a race- and sex-adjusted urine albumin-to-creatinine ratio ≥ 25 mg/g) at the year 20 examination (2005-06; baseline for this analysis) were excluded. This study included 2174 participants who had HbA1c measured at the year 20 examination and had urine albumin and creatinine measured at the year 25 examination (2010-11). Poisson regression with robust error variances was used to obtain risk ratios (RR) and 95% confidence intervals (CI) for the association of HbA1c, both as a continuous variable and dichotomous variable using its prediabetes cut-point, with albuminuria in unadjusted models and models adjusted for socio-demographics and cardiovascular risk factors. Results: During the follow-up period, 103 (4.7%) participants developed incident albuminuria. In unadjusted analyses, each 1% increase in HbA1c was associated with incident albuminuria (RR=2.55, 95% CI=1.48, 4.39). This association was attenuated and not statistically significant after adjustment for age, race, sex, and education (RR=1.68, 95% CI=0.98, 2.88) and further adjustment for cardiovascular risk factors (RR=1.42, 95% CI=0.81, 2.50). Additionally, individuals with HbA1c in the prediabetes range (5.7%-6.4%) had an increased risk of albuminuria (RR=1.59, 95% CI=1.04, 2.43) compared with those with HbA1c in the normal glycemic range (<5.7%) in the unadjusted model. However, this association was attenuated after adjustment for socio-demographics (RR=1.11, 95% CI=0.71, 1.72) and cardiovascular risk factors (RR=0.98, 95% CI=0.61, 1.55). Conclusions: After taking into account socio-demographics and traditional cardiovascular risk factors, HbA1c was not associated with incident albuminuria among individuals without diabetes.