Ethnicity, CVD Risk Factor Clustering and the Progression of Microvascular Disease: The Insulin Resistance and Atherosclerosis Study
Ethnic disparities in cardiovascular disease (CVD) and end-stage renal disease exist in the US, with African Americans (AAs) and Hispanic Americans (HAs) being at greater risk compared to non-Hispanic whites (NHWs). This maybe related to variations in individual and/or clusters of CVD risk factors across ethnic groups. We have previously shown ethnic differences in cross-sectional analyses from the Insulin Resistance and Atherosclerosis Study (IRAS) data in the effect of CVD risk factor clustering, with AAs being more greatly affected for nephropathy risk, and NHWs being more affected for CVD. We examined the effect of CVD risk factor clustering on the 5-year progression of albuminuria, which itself is a known CVD risk factor. Data were analyzed from the IRAS study, a multi-center epidemiologic cohort study that included roughly similar numbers of persons with normal and impaired glucose tolerance and type 2 diabetes, at baseline and 5-year follow-up. Comparisons were made forAAs and NHWs (Oakland/LAclinics), and for HAs and NHWs (San Antonio/San Luis Valley clinics). Data were available on 1256 IRAS subjects on nephropathy progression status, of which about 10% progressed from normal, defined as albumin/creatinine ratio less than 30 mg/g, to microalbuminuria (ACR of ≥30 and < 300) or macroalbuminuria (ACR ≥300) or from microalbuminuria to macroalbuminuria. CVD risk factors (dyslipidemia, BMI, waist-hip ratio, PAI-1, hypertension, diabetes status) at baseline were dichotomized, and subjects were classified as having high (≥ risk factors) or low (< 3 risk factors) risk. Overall 30.9% of the sample were classified as high risk. After adjusting for age, gender, and baseline nephropathy status, risk factor clustering predicted nephropathy progression in both ethnic comparisons (OR 2.24, p< 0.001 in AAs/NHWs group; OR 2.81, p< 0.001 in the HAs/NHWs group). With risk status in the model, HAs were at no greater risk for progression compared to NHWs, but risk was about 80% greater for AAs compared to NHWs (p < 0.05). These data indicate a risk of nephropathy among AAs that extends beyond the traditional CVD risk factor clusters.