Racial or ethnic and socioeconomic disparities in elevated C-reactive protein: identifying high risk groups and mediating factors

Purpose African Americans and Mexican Americans, as well as those with low socioeconomic status (SES), may be at risk for elevated C-reactive protein (CRP). To our knowledge, no research has looked at the interaction between race or ethnicity and SES on elevated CRP, or at factors that may place racial, ethnic, and SES groups at greater risk. We hypothesized that racial or ethnic minorities with low SES would have the greatest risk of elevated CRP, and that such associations would be due to factors known to be associated with elevated CRP. Methods Data from adult (age ≥ 20 years) women (n = 1990) and men (n = 1770) from the Fourth National Health and Nutrition Examination Survey (NHANES IV; 1999–2000) were used to estimate the odds of elevated CRP (>3 mg/L, as measured by high-sensitivity latex-enhanced turbidimetric assay) in the different racial or ethnic and SES (measured by educational attainment) groups. Body mass index (BMI), waist circumference, physical activity, smoking, alcohol consumption, fiber consumption, and hormone replacement therapy (in women only) were examined as potential effect modifying factors. Results Among women, Mexican Americans with low SES were the group at greatest risk for elevated CRP (odds ratio OR = 2.1, 95% confidence interval CI = 1.5–2.9). African American women tended to have a heightened risk of elevated CRP regardless of their SES, with the middle SES group having the highest risk (OR = 1.8, 1.1–3.0). White women with low SES (OR = 1.6, 1.1–2.6) were also at risk for elevated CRP. Among men, whites with low SES were the group most likely to have elevated CRP (OR = 1.6, 95% CI = 1.1–2.3). BMI and waist circumference accounted for some of the risk in Mexican American women and all of the risk in African American women. Smoking accounted for 50% of the SES association in white men and women. Conclusion Our hypothesis that low-SES minorities would be at the highest risk of elevated CRP was found to be partially true in women only, with low-SES Mexican American women at highest risk. Low-SES whites had the highest risk among men. Different mediating factors are responsible for elevated CRP in different race, ethnic, and SES groups.