Self-rated health and interleukin-6: Longitudinal relationships in older adults.

BACKGROUND: Both self-rated health (SRH) and inflammation are implicated in chronic diseases and premature mortality. Better SRH is associated with lower proinflammatory cytokines, but there is little evidence about whether this relationship is more stable or dynamic. OBJECTIVE: To study the between- and within-person associations between SRH and IL-6. METHODS: Older adults (N=131; Mage=75 years) rated their health and provided blood samples for analysis of IL-6 at separate occasions every 6 months over a period up to 5 years. Age, sex, BMI, neuroticism, and statin use were examined as covariates in multilevel models. RESULTS: In bivariate models, better SRH, lower BMI, younger age, and female sex correlated with lower IL-6. In multilevel models, stable SRH (between-person differences; p<.001) but not dynamic SRH (within-person changes; p=.93) correlated with IL-6. The stable relationship persisted with demographic and health covariates in the model. CONCLUSIONS: Better stable SRH but not dynamic SRH was robustly associated with lower IL-6 among older adults, lending support to previous cross-sectional findings on the relation between inflammatory markers and SRH. The findings suggest that trait-like mechanisms, rather than changes over a time scale of 6-month waves, govern this association. To further investigate the mechanisms behind the SRH-IL-6 association, studies with different measurement frequencies, higher within-person variability, and experimental approaches are warranted.