Racial/Ethnic Differences in Microalbuminuria Among Adults With Prehypertension and Hypertension: National Health and Nutrition Examination Survey (NHANES), 1999-2006

BACKGROUND: Microalbuminuria, a biomarker of endothelial dysfunction, is associated with increased cardiovascular, renal, and cerebrovascular morbidity and mortality, especially among ethnic minorities. METHODS: A total of 16,567 adults in the National Health and Nutrition Examination Survey (NHANES) from 1999 through 2006 were categorized according to JNC 7 blood pressure (BP) definitions. Microalbuminuria was defined as spot urinary albumin/creatinine ratio (ACR) of 30-299 mg/g. Logistic regression estimated the odds of having microalbuminuria among BP categories compared with normal BP after adjusting for age, race/ethnicity, sex, education level, smoking status, body mass index (BMI), systolic BP, and diabetes. RESULTS: Prevalence of microalbuminuria was 4.5% for normal BP, 6.3% for prehypertension, 12.4% for stage 1 hypertension, 25.3% for stage 2 hypertension, and 11.3% among those with treated, controlled hypertension. Compared with participants with normal BP, the adjusted odds ratios and 95% confidence intervals (CIs) for microalbuminuria were 1.3 (1.0-1.7, P = 0.03) for those with prehypertension, 2.3 (1.8-3.0, P < 0.01) with stage 1 hypertension, 4.8 (3.7-6.3 P < 0.01) with stage 2 hypertension, and 1.6 (1.3-2.1, P < 0.01) with treated, controlled hypertension. The treated controlled hypertension group exhibited the strongest race-ethnicity gradient. CONCLUSIONS: Participants with hypertension and prehypertension had a higher likelihood of microalbuminuria than those with normal BP, especially ethnic minorities, suggesting greater target organ damage. Our observations suggest that further research is necessary to determine whether microalbuminuria can be used as a screening tool in adults with prehypertension, to identify adults at highest risk for cardiovascular disease or decline in renal function.