A scratch-and-sniff Alzheimer’s test?

Richard Doty says people often don't appreciate their sense of smell until they'

Richard Doty says people often don't appreciate their sense of smell until they've lost it.

Richard Doty considers the sense of smell just as important to the human experience as sight or hearing.

But he says most other people—even doctors—don’t.

“It’s still ignored,” says Doty, director of the Smell and Taste Center in Penn’s School of Medicine. “I don’t think people view it as being very important.”

Doty does. As one of the world’s leaders in smell and taste research, Doty in the 1980s helped develop a test, called the University of Pennsylvania Smell Identification Test, now considered the international standard for measuring olfactory ability. He has also worked to find the link between the sense of smell and various diseases.

Most recently, Doty and researchers at Columbia garnered international attention when their research proved a person’s ability—or inability— to identify 10 specific odors could be used as a test to predict likelihood of Alzheimer’s disease, which affects about 4.5 million Americans.

The 10 odors are smoke, menthol, leather, lilac, pineapple, soap, strawberry, natural gas, lemon and clove, and the test Doty developed based on those odors has proven to be just as effective at predicting Alzheimer’s as a memory test—and more effective than a brain scan.

“The bottom line of the research is that there’s a subset of 10 odors that are particularly good at making the differentiation between someone who goes from mild cognitive decline to getting Alzheimer’s,” Doty says. That’s because the area of the brain responsible for smell is near the area most directly attacked by Alzheimer’s.

For the research, Doty and his colleagues asked 150 patients with mild cognitive dysfunction and 63 subjects with no memory problems to identify odors from “scratch-and-sniff” style cards.

While the healthy subjects scored between 35 and 40 on the smell test, those with mild memory problems scored in the 20s, researchers found. They also found the test subjects who were unable to identify more than two of the 10 selected smells were nearly five times more likely to develop full-blown Alzheimer’s than those that scored better.

The research, presented in December at a meeting of the American College of Neuropharmacology in San Juan, PR, was picked up by the media in the U.S. and overseas.

Doty note that although mounting evidence has linked smell dysfunction to such brain conditions as Alzheimer’s and Parkinson’s , not all people with smelling problems should worry about Alzheimer’s.

“If you have a smelling problem, it doesn’t mean you have Alzheimer’s. ... or anything like that,”Doty said. “Smell loss can also be a sign of very many other things.”

Exposure to certain chemicals, a respiratory infection or head trauma can also cause smell loss, he said.

Originally published on February 10, 2005