Peripheral inflammatory biomarkers may play an important role in the cognitive decline of aging and incidence of Alzheimer's disease (AD); however, data from epidemiological studies present conflicting findings. The purpose of the current review was to systematically determine the current state of the science on the association between peripheral inflammatory biomarkers and cognitive decline. Articles published from January 1, 2006 to October 28, 2016 were searched using the Medline and Embase databases. Nine studies met inclusion criteria (two examined participants with AD dementia and seven examined participants without dementia). Although a wide range of peripheral inflammatory biomarkers was examined, C-reactive protein and interleukin 6 were the most studied. Findings show conflicting results for the association between peripheral inflammatory biomarkers and cognitive decline. Peripheral inflammation may harm and help the brain, and therefore, the challenge of modulating immunity will be to find ways of fine tuning inflammation to delay, prevent, or treat AD.
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