It turns out that the Alzheimer's disease could be already "at work" in the brain while the actual symptoms appear years later.
Indiana University investigators showed that the best-known genetic variant linked to Alzheimer's disease may be promoting deposits of plaque in the brain long before any symptoms of the disease can be measured on tests.
The study focused on people with "significant memory concerns," defined as older adults who complained that they had mentally slipped in recent months or years, but when given standard cognition and memory tests they fell within normal ranges. People in this category have also been called the "subjective cognitive decline" group by Alzheimer's researchers.
The paper's authors, led by Shannon L. Risacher, Ph.D., and Andrew J. Saykin, Psy.D., looked at data from nearly 600 ADNI participants, the researchers compared those with the gene in question, APOE e4, variant to those with other forms of the gene. In the "significant memory concerns" group the researchers found evidence of Alzheimer's-like pathologies from several biomarkers among the APOE e4 carriers including:
Increased levels of amyloid plaque, the clumps of protein fragments commonly found in the brain tissue of Alzheimer's patients.
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In the cerebrospinal fluid, decreased levels of the protein precursor to the plaques, suggesting that the protein was being recruited to the brain as part of the plaque creation process.
In the cerebrospinal fluid, increased levels of tau, another protein associated with Alzheimer's disease.
However, the analysis did not find evidence of reduced levels of glucose metabolism nor atrophy of brain structures that are associated later stages of Alzheimer's progression.
The study provides the foundation for further focused research among patients at risk of Alzheimer's earlier than in much other research, Dr. Risacher said.
The research is published in the journal Alzheimer's and Dementia.
