Socioeconomic Differentials in Immune Response

Background: Lower socioeconomic status (SES) is strongly linked to health outcomes, though the mechanisms are poorly understood. Little is known about the role of the immune system in creating and sustaining health disparities. Here we test whether SES is related to cell-mediated immunity, as measured by the host's ability to keep persistent cytomegalovirus (CMV) antibody levels in a quiescent state. Methods: Censored regression models were used to test the cross-sectional relationship of education, income, and race/ethnicity with antibody response to CMV, using a nationally representative sample of 9721 respondents aged 25 years and older in the Third National Health and Nutrition Examination Survey (NHANES III, 1988-1994). Results: Among CMV-seropositive respondents, those with less education, lower income, and nonwhite race/ethnicity had higher levels of CMV antibodies at all ages. On average, each additional year of age was associated with CMV antibody levels that were 0.03 units higher (95% confidence interval = 0.03 to 0.04), whereas each additional year of education was associated with antibody levels that were 0.05 units lower (0.02 to 0.09). A doubling of family income was associated with antibody levels that were 0.25 units lower (0.11 to 0.39), the equivalent of 8 fewer years of age-related CMV antibody response. These relationships remained strong after controlling for baseline health conditions, smoking status, and BMI. Conclusions: SES is associated with an indirect marker of cell-mediated immunity in a nationally representative sample. SES differences in immune control over CMV may have fundamental implications for health disparities over the life course.