Income and Markers of Immunological Cellular Aging

Abstract

Objective: Socioeconomic disadvantage may contribute to poor health through immune-related biological mechanisms. We examined the associations between socioeconomic status, as measured by annual household income, and T-cell markers of aging, including the ratios of CD4 and CD8 effector cells to naïve cells (E/N ratio) and the CD4/CD8 T-cell ratio. We hypothesized that participants with a lower income would have higher E/N ratios and lower CD4/CD8 ratios compared with participants with a higher income, and that these associations would be partially mediated by elevated cytomegalovirus (CMV) IgG antibody levels, a virus implicated in aging and clonal expansion of T cells.

Methods: Data were from 79 individuals who participated in the population-based Detroit Neighborhood Health Study. We used linear regression to quantify the association between a $10,000 decrease in income and each ratio outcome.

Results: After adjustment for age, sex, race, smoking, medication use, and lifetime history of mental health conditions, lower income was associated with a 0.41 (95% confidence interval = 0.09-0.72) log-unit increase in the CD4 E/N ratio and a 0.20 (95% confidence interval = 0.02-0.39) log-unit increase in the CD8 E/N ratio. CMV immunoglobulin G antibody level partially mediated these associations.

Conclusions: Our study suggests that low socioeconomic status is associated with immunological aging as measured by the E/N ratio and that impaired immune control of CMV may partially mediate these associations.

Figure 1. Associations between each $10K decrease in annual household income and the distribution of T cell phenotypes among 79 participants in the Detroit Neighborhood Health Study

Abbreviations: CMV, cytomegalovirus; E:N ratio, ratio of end-stage non-proliferative effector cells (E; CCR7−CD45RA+CD27−CD28− or TEMRA) to naïve T-cells (N; CCR7+CD45RA+CD27+CD28+) Triangles and corresponding bars indicate the β and 95% confidence intervals for a log unit increase in each outcome associated with a $10,000 decrease in annual household income. *p value <0.10 **p value <0.05 Model 1: adjusted for age, sex and race. Model 2: adjusted for age, sex, race, smoking status, medication use, and lifetime history of mental health conditions.

Figure 2. Estimation of the direct and indirect effects of each $10,000 decrease in annual family income on the distribution of T-cell phenotypes among 79 participants in the Detroit Neighborhood Health Study

Abbreviations: CMV, cytomegalovirus; E:N ratio, ratio of end-stage non-proliferative effector cells (E; CCR7−CD45RA+CD27−CD28− or TEMRA) to naïve T-cells (N; CCR7+CD45RA+CD27+CD28+) *p value <0.10 **p value <0.05