Markers of inflammation and cognitive decline in an African‐Caribbean population

Background Inflammatory processes may play an important role in cognitive decline and dementia. We investigated the prospective association between levels of three markers of inflammation, plasma interleukin-6 (IL-6), serum C-reactive protein (CRP), serum amyloid A (SAA), and cognitive decline in an African-Caribbean community population. Methods Of 290 participants aged 55–75 years at baseline sampled from Primary Care registration lists in south London, 216 (75%) were re-interviewed after 3 years. Baseline plasma concentrations of IL-6, CRP and SAA were ascertained through immunoassays. A battery of psychometric tests was administered on both occasions and decline in both individual tests and a composite outcome was analysed. Results After adjustment for potential confounding factors, raised levels of IL-6 (>3.1 pg/ml) were associated with cognitive decline in the total sample (odds ratio 2.9, 95% CI 1.1–7.5), but no associations were found for CRP or SAA. Raised IL-6 was most strongly associated with decline in orientation and immediate verbal recall tasks, with weaker associations for delayed recall and psychomotor speed. Conclusions Raised IL-6 but not CRP predicted cognitive decline in this population Inflammatory changes associated with cognitive decline may be specific to particular causal pathways. Copyright © 2007 John Wiley & Sons, Ltd.