Posted on Fri, Dec. 24, 2004




Your nose can predict Alzheimer's, study says

Penn research links risk to ability to detect smells.

By Stacey Burling

Inquirer Staff Writer

The inability to identify the smell of lemons, lilacs and eight other
common scents predicts who is most likely to get Alzheimer's disease,
according to new research.

People who failed to recognize these scents were at higher risk for
developing Alzheimer's disease than those with more discriminating
noses, the study found.

Researchers measured how well people with mild cognitive impairment -
memory problems that often precede Alzheimer's - could smell. Those
who misidentified more than two of the 10 scents were nearly five
times more likely to progress to Alzheimer's than those who did
better, said Richard Doty, director of the University of
Pennsylvania's Smell and Taste Center.

Doty developed a 40-item, multiple-choice scratch-and-sniff test that
New York researchers used in the study. Their goal was to see whether
a shorter exam could just as effectively weed out people likely to
develop more serious memory problems.

D.P. Devanand, a Columbia University psychiatrist who led the study,
said that the shorter smell test was comparable to memory tests and
outperformed MRI scans of brain volumes at predicting which patients
would progress to Alzheimer's.

In the future, when better treatments are available, this kind of test
could help patients combat the disease earlier in its course, Devanand
said.

Doctors have known for years that people with Alzheimer's disease have
impaired olfactory function, Doty said. That is probably because
Alzheimer's first attacks the part of the brain that controls ability
to smell.

The University of Pennsylvania test is in use in thousands of clinics
throughout the world, said Doty, who participated in the Columbia
study. He also owns Sensonics, a company that sells the test.

"It's sort of the eye chart of the nose," he said.

The test is meant to be fairly easy for people with a normal sense of
smell, Doty said. Test takers, for example, are asked if they are
smelling lemon or motor oil, lilac or whiskey.

Doty estimates that 25 scientific papers have been written on the
connection between performance on the olfactory exam and Alzheimer's.

In Devanand's research, presented this month at the American College
of Neuropsychopharmacology annual meeting, the other scents that best
predicted Alzheimer's were: strawberry, soap, smoke, menthol, clove,
pineapple, natural gas and leather. Another five were poor predictors
because people with Alzheimer's did as well normal people. They are:
cheddar cheese, lime, grass, orange and fruit punch.

Beverly J. Cowart, a psychologist who directs the Monell Chemical
Senses Center in Philadelphia, said doctors would probably always need
more than the scent test for diagnosis because the sense of smell is
also impaired in Parkinson's and Huntington's disease and in old age
in general. Viruses, sinus disease, and exposure to certain chemicals
also mess up the olfactory system.

"Smell testing may be a useful adjunct in diagnosis, but I don't think
it's ever going to be the bedrock of a diagnosis of Alzheimer's," she
said.

Impaired smelling ability may also predict who develops schizophrenia,
said Paul Moberg, a University of Pennsylvania psychologist who
studies smell and the severe psychiatric disease.

Even early in the course of schizophrenia, which usually becomes
noticeable in late adolescence or early adulthood, the ability to
detect and identify scents is diminished, he said. The problem worsens
over time.

An Australian researcher recently found that patients at risk for
schizophrenia were more likely to develop the disease if they had
trouble identifying scents.

The part of the brain responsible for smelling, the olfactory bulb, is
smaller in schizophrenics than in other people, Moberg said. Nasal
cavities are also smaller in people with the disease, he reported this
month in the American Journal of Psychiatry. Studying smell, he said,
may help scientists figure out when schizophrenia begins - most
researchers think it starts in the womb - and follow its progression.

While a good sense of smell isn't as important to humans as it is to
animals, it makes a big difference in how food tastes, Cowart said.
And, being able to smell something like natural gas - or,
specifically, the scent added to it, because natural gas is odorless -
can be a lifesaver.

"For human beings, it's to a large extent a quality-of-life issue,"
Cowart said. "I think humans sometimes don't appreciate how much they
use their sense of smell."