Current Understanding: |
The tables below present a modest number of reports whose results, considered collectively, do not provide consistent support for an association between elevated peripheral blood levels of inflammatory markers (C-reactive protein [CRP], interleukin-6 [IL-6], alpha-1-antichymotrypsin [ACT], fibrinogen, lipoprotein-associated phospholipase A2 [Lp-PLA2], interleukin-1β [IL-1β] ) and risk for Alzheimer disease (AD). Associations between higher levels of these markers and total dementia risk are more suggestive, consistent with a reported link between vascular inflammation and vascular dementia. Individual markers were significantly associated with AD in some studies, but the evidence overall was inconsistent. The ability of peripheral inflammatory markers to represent inflammation in the central nervous system (CNS) is limited, and future studies may provide more clarity on the distinction between the roles of peripheral and CNS inflammation by identifying and measuring brain-specific markers of inflammation. In addition, it is possible that measurement of an overall inflammatory profile, particularly as it unfolds over time, may provide a much better test of the inflammatory hypothesis than individual markers measured on a single occasion. In the meantime, inflammatory responses might have an impact on disease progression, and could be the basis for developing and monitoring therapeutic treatments. For a review of the putative mechanisms by which inflammatory biomarkers may be related to AD risk and detailed commentary on interpreting the findings below in a broader context, please view the Discussion. A longer review and discussion of CRP and IL-6 can be found in the related earlier published review and meta-analysis, Koyama A, O’Brien J, Weuve J, Blacker D, Metti A, Yaffe K. The role of peripheral inflammatory markers in dementia and Alzheimer’s disease: A meta-analysis (J Gerontol A Biol Sci Med Sci 2013 April;68(4):433-440). |
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