Association between life-course socioeconomic position and inflammatory biomarkers in older age: a nationally representative cohort study in Taiwan

BACKGROUND Evidence of an association between low socioeconomic position (SEP) and inflammatory markers is scant. This study aimed to examine how life-course SEP predicted C-reactive protein (CRP) and interleukin (IL-6) in older age from a national cohort. METHODS We collected data from 1036 participants in the Social Environment and Biomarkers of Aging Study in Taiwan. Four SEP time points, childhood, young adulthood, active professional life, and older age were measured retrospectively. A group-based trajectory analysis method was used to identify the distinct trajectories of life-course SEP, and trajectory group membership was used as the predictor of CRP and IL-6 levels in older age. RESULTS Three trajectories of life-course SEP were identified within the total sample: Low-Low (36.5%), Low-High (26.8%), and High-High (36.7%). Participants in the High-High group had the lowest levels of CRP and IL-6. Compared with those in the Low-Low group, the participants in the Low-High group had a similar adjusted CRP [-0.032 ln mg/L; 95% confidence interval (CI) - 0.193, 0.128] and IL-6 (0.017 ln pg/mL; 95% CI -0.093, 0.128); the participants in the High-High group had a significantly lower level of adjusted CRP concentration (-0.279 ln mg/L; 95% CI: -0.434, -0.125) and similarly lower IL-6 concentration (-0.129 ln pg/mL; 95% CI -0.236, -0.023) . CONCLUSIONS Life-course SEP is related to the level of CRP and IL-6 in older age. Our data support the notion that life-course SEP predicts inflammatory markers in older age. Low SEP in childhood is related to elevated inflammatory markers in older age. Even after the transition from low SEP in childhood to high SEP in older age, the risk remains. Further study on SEP and inflammation-related disease is warranted.