Low blood levels of beta-amyloid 42, a protein-like substance, were associated with the risk of significant cognitive decline within nine years in a group of elders, in a study led by Kristine Yaffe, MD, chief of geriatric psychiatry at the San Francisco VA Medical Center.
Beta-amyloid 42 has long been known to collect in the brain of patients with Alzheimer's disease.
The study also showed that, among the elders with low beta-amyloid 42,cognitive decline was less pronounced in those who had higher literacy, or more education, or who lacked the APOE e4 gene known to be associated with a greater risk of dementia. The researchers describe this set of conditions as "cognitive reserve."
The study appears in the January 19, 2011 issue of the Journal of the American Medical Association.
"We show that a blood test for beta-amyloid 42 might be a good way to predict those at risk for cognitive decline," said Yaffe. "Also, for the first time, we show that cognitive reserve - a general level of resiliency in the brain - might modify that risk in the elderly."
Yaffe, who is also associate chair for clinical and translational research in psychiatry and professor of psychiatry, neurology, and epidemiology and biostatistics at the University of California, San Francisco, described the findings as "potentially of great importance for clinical care of Alzheimer's disease and dementia."