Determine Early Stages Of Alzheimer's Disease Through Testing The Eyes And Nose Function

First Posted: Jul 27, 2016 06:26 AM EDT

There have been continuous efforts to detect Alzheimer's disease way before memory symptoms even begin to show. Researchers at the Alzheimer's Association International Conference in Toronto this week presented new data suggesting that a subtle shift in a person's sense of sight and smell may offer early signs of the disease.

Two studies suggested that older adults with a decreasing ability to identify odors may already started to have a decline in cognitive functions. According to CNN, other studies probed on different types of eye tests to help them determine the disease. These were all presented during the Alzheimer's Association International Conference 2016 Tuesday in Toronto.

As many may have already known, Alzheimer's is the most common type of dementia which causes a person to have problems with memory, thinking and behavior.

It looks like "the eyes and the nose are a window to the brain," observed CBS News medical contributor Dr. David Agus.

One of the studies revealed that the thinning of the retinal nerve fiber layer in the eye could happen to those who performed poorly in the testing of cognitive skills like memory, reasoning and reaction time.

Agus, who appeared on "CBS This Morning," said the finding makes sense. "If you look in the eye, the retinal nerve that comes out of the brain, if it gets narrower, that's an indicator of the onset of Alzheimer's."

Meanwhile, aside from MRI scan that measured the thickness of the brain area where Alzheimer's typically first develops, the entorhinal cortex, one of the studies used the smell test on 397 adults in Manhattan. These men were 80 years old, on average, and didn't have dementia. The study involved 40 scratch-and-sniff surfaces scented with a range of familiar scents including turpentine, lemon, licorice, bubble gum and even "eau de skunk."

It was found that fifty of these people (12.6 percent) had dementia four years after undergoing the initial smell test, while nearly 20 percent showed signs of cognitive decline.

Basically, Agus said that if a person can name 35 out of the 40 scents, then that person has a lower chance of developing Alzheimer's. However, if you got less than 35 scents correct, you may have already started the process of developing the disease condition, US News reported.

Researchers cleared out that it is not the sensitivity of the nose that diminishes; it is the cognitive impairment that's developing. The brain is not very capable of identifying what those smells are.

"Our research showed that odor identification impairment, and to a lesser degree, entorhinal cortical thickness, were predictors of the transition to dementia," study author Seonjoo Lee, assistant professor of clinical biostatistics (in psychiatry) at Columbia University Medical Center, said in a statement. "These findings support odor identification as an early predictor, and suggest that impairment in odor identification may precede thinning in the entorhinal cortex in the early clinical stage of Alzheimer's disease."

"Our study adds to the growing body of evidence demonstrating the potential value of odor identification testing in the detection of early-stage Alzheimer's disease," senior author of both studies D.P. Devan and, professor of psychiatry at Columbia University Medical Center, said in the same statement.

At present, Alzheimer's disease can only be clinically determined during the disease's later stage, after the brain has already been severely damaged. There are approximately 5.4 million Americans who are suffering from  Alzheimer's, according to the Alzheimer's Association.

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