Alzheimer's Potentially Detected with Smell, Eye Tests

Alzheimer's disease, the most common form of dementia among older adults, can possibly be detected early on with simple smell and eye tests, according to four new research trials presented at the Alzheimer's Association International Conference over the weekend.

The decreased ability to identify odors might indicate the development of cognitive impairment and Alzheimer's disease, two of the studies suggest, while the build-up of beta-amyloid, a protein associated with Alzheimer's, in the brain, is also a sign, another study showed. Simple smell and eyes exams administered to patients could possibly detect Alzheimer's before other, more obvious symptoms present themselves.

"In the face of the growing worldwide Alzheimer's disease epidemic, there is a pressing need for simple, less invasive diagnostic tests that will identify the risk of Alzheimer's much earlier in the disease process," Heather Snyder, Ph.D., Alzheimer's Association director of Medical and Scientific Operations, said in a statement. "This is especially true as Alzheimer's researchers move treatment and prevention trials earlier in the course of the disease."

According to the US Centers of Disease Control and Prevention, up to five million Americans suffer from Alzheimer's, usually starting at age 60. Scientists do not yet fully understand what causes this debilitating disease, and currently it's only possible to identify it late in its development, when significant brain damage has already occurred.

One example of too-little too-late technology are brain PET scans, designed to detect the beta-amyloid protein - the primary material found in the sticky brain "plaques" characteristic of Alzheimer's disease. It's known it build up in the brain years before typical Alzheimer's symptoms are noticed, like memory loss and other cognitive problems. Unfortunately, these scans are expensive and not available everywhere, so a routine eye exam meant to detect plaques in the retina may be a more affordable solution.

In one of the studies, such a test was given to participants, and was found to differentiate between Alzheimer's and non-Alzheimer's patients with 100 percent sensitivity.

There is also growing evidence that failure to correctly identify smells is a mark of Alzheimer's. As the disease begins to kill brain cells, this often includes cells that are important to the sense of smell.

Researchers administered the University of Pennsylvania Smell Identification Test (UPSIT) test, as well as several cognitive tests, to investigate the relationship between sense of smell and memory performance. After also measuring the size of certain brain structures, they found that a smaller hippocampus and a thinner entorhinal cortex were associated with worse smell identification and worse memory in participants.

"Our research suggests that there may be a role for smell identification testing in clinically normal, older individuals who are at risk for Alzheimer's disease," said Matthew E. Growdon, leader of one of the studies.

Both the smell and eye tests could possibly revolutionize the way scientists detect people with Alzheimer's disease. Just two years ago, the United States created its first National Plan to Address Alzheimer's Disease - with the support of the Alzheimer's Association - aimed to prevent and effectively treat Alzheimer's by 2025.