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Alzheimer's disease: does the nose know?

An insidious disease, Alzheimer's can start to develop long before one can detect troublesome losses in cognitive function. However, people with this disease also lose some of their sense of smell. Researchers hope that monitoring changes in this sense will help them detect the disease earlier and aid in tracking its progression.

"The goal is to develop an early marker or something that could [change] along with the disease;' explains Jack Pearl of the National Institute on Deafness and Other Communication Disorders in Bethesda, Md. "An olfactory test is a relatively noninvasive way of testing."

Toward that end, several research groups have begun studying the ability of older people, with and without Alzheimer's, to detect and remember odors.

In a study conducted at the University of California, San Diego, Medical Center, 65 people with Alzheimer's disease and 82 healthy people of similar ages and backgrounds underwent vision, taste, and odor tests. The vision and taste components helped the scientists determine whether the participants were of sound enough mind for testing and whether deterioration had occurred in more than one sense.

One of the odor tests required participants to sniff alcohol from pairs of plastic squeeze bottles and pick out the one with the stronger scent. By supplying bottles with different concentrations of alcohol, the researchers could tell at what concentration the person first detected the odor. The same people also sipped sugar water samples with differing degrees of sweetness and were asked to spit out the sweeter one.

Participants with Alzheimer's needed much stronger odors than the healthy sniffers, say Claire Murphy and Steven Nordin, who led the study "The more demented [the person], the higher the threshold, but there was no such correlation for taste;' adds Nordin. "The research suggests there is a specific detection dysfunction to odors."

Furthermore, he notes, in the seven people with Alzheimer's disease who have now been tested for three years, the average yearly change in the odor-detection threshold has correlated with the progression of dementia.

A second experiment assessed the participants' ability to recognize odors they had smelled earlier. Each person looked at 10 faces of presidents and 10 engineering symbols and smelled 10 common household odors. They then examined a second set of faces, symbols, and odors, half of which came from the first set. Participants tended to score the same when rating familiar faces and symbols as when rating odors they had sniffed earlier. But Alzheimer's patients scored lower overall, indicating a general decline in memory, says Nordin.

At Duke University in Durham, N.C. psychologist Susan S. Schiffman and her colleagues track changes in healthy people who are at risk of developing Alzheimer's. So far, the study involves 22 such individuals and 22 people matched for age, gender, race, level of education, and handedness who are not considered at risk for the disease. Participants undergo several tests, including ones in which they pick the stronger of two flavors or odors and are asked to remember familiar ones.

The two groups differ only in their ability to remember odors, reports Brevick G. Graham of Duke.

"l wouldn't suggest that [odor testing] would ever replace any of the cognitive measures, but it might be used in addition to other things for early diagnosis of Alzheimer's," he says.
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Title Annotation:loss in sense of smell may detect Alzheimer's disease and track its progression
Author:Pennisi, Elizabeth
Publication:Science News
Article Type:Brief Article
Date:May 8, 1993
Previous Article:Foods that fool the body with low fat.
Next Article:There's no accounting for taste.

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