"Plasma levels of amyloid-β (Aβ) peptides have been a principal focus of the growing literature on blood-based biomarkers, but studies to date have varied in design, assay methods, and sample size, making it difficult to readily interpret the overall data," the authors write as background in the study.
Alain Koyama, S.M., then of Harvard School of Public Health and Brigham and Women's Hospital, Boston, now with the University of California, San Francisco, and colleagues conducted a meta-analysis of 13 previously published studies to examine the association between plasma amyloid-β and development of dementia, Alzheimer disease (AD) and cognitive decline.
The 13 studies included in the analysis had a total of 10,303 participants, and were published between 1995 and 2011. The studies also included measurement of at least one relevant plasma amyloid-β species (Aβ40, Aβ42, or Aβ42: Aβ40 ratio) and reported an effect estimate for dementia, AD or cognitive decline.
The authors found that lower Aβ42: Aβ40 ratios were significantly associated with development of Alzheimer disease and dementia, with most studies in the analysis reporting similar findings. Plasma levels of Aβ40 and Aβ42 alone, however, were not significantly associated with either outcome.
"In conclusion, despite the limitations of existing research and heterogeneity across the studies considered, this systematic review and meta-analysis suggests that the ratio of plasma Aβ42: Aβ40 may have value in predicting the risk for later development of dementia or AD and merits further investigation."
(Arch Neurol. Published online March 26, 2012. doi:10.1001/archneurol.2011.1841. Available pre-embargo to the media at www.jamamedia.org.)
Editor's Note: This study was funded by a grant from the National Institutes of Health. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.
For more information, contact JAMA/Archives Media Relations at 312-464-JAMA (5262) or email mediarelations@jama-archives.org.
Media Advisory: To contact Alain Koyama, S.M., call Lori Shanks at 617-534-1604 or email ljshanks@partners.org.
Journal
Archives of Neurology