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.