Inflammatory markers and cognition in well-functioning African-American and white elders

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Abstract
Background: Several lines of evidence suggest that inflammatory mechanisms contribute to AD. Objective: To examine whether several markers of inflammation are associated with cognitive decline in African-American and white well-functioning elders. Methods: The authors studied 3,031 African-American and white men and women (mean age 74 years) enrolled in the Health, Aging, and Body Composition Study. Serum levels of interleukin-6 (IL-6) and C-reactive protein (CRP) and plasma levels of tumor necrosis factor-α (TNFα) were measured at baseline; cognition was assessed with the Modified Mini-Mental State Examination (3MS) at baseline and at follow-up. Cognitive decline was defined as a decline of >5 points. Results: In age-adjusted analyses, participants in the highest tertile of IL-6 or CRP performed nearly 2 points lower (worse) on baseline and follow-up 3MS (p < 0.001 for all) and declined by almost 1 point over the >2 years (p = 0.01 for IL-6 and p = 0.04 for CRP) compared with those in the lowest tertile. After multivariate adjustment, 3MS scores among participants in the highest tertile of IL-6 and CRP were similar at baseline but remained significantly lower at follow-up (p ≤ 0.05 for both). Those in the highest inflammatory marker tertile were also more likely to have cognitive decline compared with the lowest tertile for IL-6 (26 vs 20%; age-adjusted odds ratio [OR] = 1.34; 95% CI 1.06 to 1.69) and for CRP (24 vs 19%; OR = 1.41; 95% CI 1.10 to 1.79) but not for TNFα (23 vs 21%; OR = 1.12; 95% CI 0.88 to 1.43). There was no significant interaction between race and inflammatory marker or between nonsteroidal anti-inflammatory drug use and inflammatory marker on cognition. Conclusions: Serum markers of inflammation, especially IL-6 and CRP, are prospectively associated with cognitive decline in well-functioning elders. These findings support the hypothesis that inflammation contributes to cognitive decline in the elderly.