According to the results of four research trials presented at the Alzheimer’s Association International Conference (AAIC) in Copenhagen, a decreased ability to identify odors might indicate the development of Alzheimer’s disease, while examinations of the eye could indicate the build-up of beta-amyloid, a protein associated with Alzheimer’s.
In two of the studies, the decreased ability to identify odors was significantly associated with loss of brain cell function and progression to Alzheimer’s disease. In two other studies, the level of beta-amyloid detected in the eye (a) was significantly correlated with the burden of beta-amyloid in the brain and (b) allowed researchers to accurately identify the people with Alzheimer’s in the studies.
Beta-amyloid protein is the primary material found in the sticky brain “plaques” characteristic of Alzheimer’s disease. It is known to build up in the brain many years before typical Alzheimer’s symptoms of memory loss and other cognitive problems.
Clinically, at this time it is only possible to detect Alzheimer’s late in its development, when significant brain damage has already occurred. Biological markers of Alzheimer’s disease may be able to detect it at an earlier stage. For example, using brain PET imaging in conjunction with a specialized chemical that binds to beta-amyloid protein, the buildup of the protein as plaques in the brain can be revealed years before symptoms appear. These scans can be expensive and are not available everywhere. Amyloid can also be detected in cerebrospinal fluid through a lumbar puncture where a needle is inserted between two bones (vertebrae) in your lower back to remove a sample of the fluid that surrounds your brain and spinal cord.
There is growing evidence that the decreased ability to correctly identify odors is a predictor of cognitive impairment and an early clinical feature of Alzheimer’s. As the disease begins to kill brain cells, this often includes cells that are important to the sense of smell.
Matthew E. Growdon, B.A., M.D./M.P.H. candidate at Harvard Medical School and Harvard School of Public Health, and colleagues investigated the associations between sense of smell, memory performance, biomarkers of loss of brain cell function, and amyloid deposition in 215 clinically normal elderly individuals enrolled in the Harvard Aging Brain Study at the Massachusetts General Hospital. Growdon reported at AAIC that in a subgroup of study participants with elevated levels of amyloid in their brain, greater brain cell death, as indicated by a thinner entorhinal cortex, was significantly associated with worse olfactory function — after adjusting for variables including age, gender, and an estimate of cognitive reserve.
Davangere Devanand, M.B.B.S., M.D., Professor of Psychiatry at Columbia University Medical Center reported that in 757 subjects followed, lower odor identification scores on UPSIT were significantly associated with the transition to dementia and Alzheimer’s disease.
“There is a critical need for a fast, dependable, low-cost and readily available test for the early diagnosis and management of Alzheimer’s disease,” said Pierre N. Tariot, M.D., Director of the Banner Alzheimer’s Institute in Phoenix. “These results show promise as a technique for early detection and monitoring of the disease.”