Plasma cytokine levels in a population-based study: Relation to age and ethnicity

Background. Aging is one factor believed to contribute to processes that underlie chronic low-grade inflammation in older adults. Moreover, more recent studies have suggested that cytokine levels are influenced by ethnicity. Methods In this study, we determined plasma cytokine profiles in a population-based sample (n = 1,411; aged 25-91 years) to determine the relationship between circulating cytokine levels, aging, and ethnicity. We measured interleukin-1 receptor antagonist (IL-1ra), interleukin (IL)-6,-10, C-reactive protein (CRP), and tumor necrosis factor-receptor 1 (TNF-r1). Results IL-6 and TNF-r1 significantly increased with age, whereas IL-1ra, IL-10, and CRP did not significantly increase with age. After adjusting for age, non-Hispanic whites had significantly higher levels of IL-1ra than Mexican Americans, whereas non-Hispanic blacks had significantly higher levels of IL-6 and CRP than Mexican Americans as well as non-Hispanic whites. CRP levels in non-Hispanic blacks were no longer significantly higher after adjusting for body mass index (BMI), indicating that BMI is an important predictor of this inflammatory marker. Conclusions These Results demonstrate that cytokine levels are influenced by both age and ethnicity. Furthermore, these Results show that inflammatory profiles for Mexican Americans are lower than non-Hispanic whites and non-Hispanic blacks.