Dulled Sense of Smell Might Predict Alzheimer's

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"The idea is attractive, since the smell area of the brain is involved in the course of the disease," Gandy said.

And yet, "reports that problems with a person's sense of smell may be an early indicator of memory and thinking problems have appeared in the scientific literature at several occasions over the past 20 years," he pointed out. Still, "no observation has been particularly strong nor have they been replicated by other scientists," Gandy said.

More detailed studies are needed to assess the possibility of a connection between smelling ability and changes in mental function, he said.

"These tests should be tested on one group of people and then subjected to double-blind assessment in a second or third population before scientists begin to make claims that a particular smell test is associated with or predictive of imminent or incident cognitive dysfunction," he said.

But Richard L. Doty, director of the Smell and Taste Center of the University of Pennsylvania Medical Center in Philadelphia -- who developed the smell test used in the Wilson study -- said the test has already been used on a limited basis in clinical practice.

"It was given to relatives of persons with both Parkinson's disease and Alzheimer's disease who were normal," Doty said. "It showed that there was a loss of the ability to distinguish odors in those who eventually converted to the disease. Some neurologists have been using it in differential diagnosis."

The test used in the Rush study can be administered (or taken by the person being tested) in about five minutes, Wilson said. "But I'm not recommending that everyone run out and have this test administered," he said.

Diagnosis using smell testing or other methods would do a patient no real good, Wilson reasoned, because there's still no effective treatment to halt the progression of Alzheimer's disease. However, "the field is expecting that that will change in the next few years," he said.

Medications that target the accumulation of amyloid deposits in the brain, which many believe to be involved with the development of Alzheimers disease, are showing promise, Wilson said. "If these agents are effective in combating the accumulation of amyloid in the brain, they could alter the course of the disease," he said.