Gender, race/ethnicity, personality, and interleukin-6 in urban primary care patients

Abstract

Gender, race/ethnicity, and personality are markers of significant psychosocial and biological variability. Each may have implications for allostatic load and resulting inflammatory processes, yet findings have been largely mixed. We investigated whether women, minorities, and those higher in Neuroticism and lower in Extraversion were at risk for elevated circulating levels of the pro-inflammatory cytokine interleukin (IL)-6 in a sample of 103 middle aged and older urban primary care patients. Regression analyses controlling for age, education, current depression levels, and chronic medical conditions revealed that women, minorities, and individuals lower in Extraversion had higher circulating levels of IL-6. Analyses of more specific personality traits revealed that the sociability and positive emotions components of Extraversion were unassociated with IL-6, but the activity facet-reflecting dispositional vigor and energy-was robustly associated with IL-6. The difference between high (+1 Standard Deviation (SD)) and low (-1 SD) trait activity was sufficient to shift IL-6 levels beyond a previously established high risk cut-point in both white and minority women. These findings suggest that while broad group differences between genders and races/ethnicities exist, personality represents an important source of individual differences in inflammation within groups. Future work should examine to what extent IL-6 levels are linked to temperament or genetic activity levels vs. physical activity itself, and whether IL-6 levels may be reduced by boosting regular activity levels in demographic segments such as women and minorities who appear susceptible to greater inflammation.

Figure 1. Associations of Difference Extraversion Subcomponents With IL-6

Note. Adjusted for age, gender, education, illness burden, current depressive symptoms, and Neuroticism

Figure 2. Incremental Variance Explained in IL-6 by Race/Ethnicity, Gender, and Trait Activity

Note: Increments to R² and Adjusted R² from adding denoted variables in hierarchical regression.

Figure 3. Model 6 Predicted IL-6 Means for Combinations of Gender, Race/Ethnicity, and Trait Activity

Note. Model 6 predicted values for different configurations of gender, race/ethnicity, and activity level, holding other covariates at mean values. Horizontal line marks IL-6 level of 3.19 pg/ml identified in prior epidemiologic work (Harris et al., 1999) as threshold doubling mortality risk.