Milenko Kindl

CHICAGO - Difficulty identifying common smells such as lemon, banana
and cinnamon may be the first sign of Alzheimer's disease, according
to a study that could lead to scratch-and-sniff tests to determine a
person's risk for the progressive brain disorder.
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Such tests could be important if scientists find ways to slow or stop
Alzheimer's and the severe memory loss associated with it. For now,
there's no cure for the more than 5 million Americans with the
disease.

Researchers have long known that microscopic lesions considered the
hallmarks of Alzheimer's first appear in a brain region important to
the sense of smell.

"Strictly on the basis of anatomy, yeah, this makes sense," said
Robert Franks, an expert on odor perception and the brain at the
University of Cincinnati. Franks was not involved in the new study,
appearing in Monday's Archives of General Psychiatry.

Other studies have linked loss of smell to Alzheimer's, Franks said,
but this is the first to measure healthy people's olfactory powers and
follow them for five years, testing along the way for signs of mental
decline.

In the study, 600 people between the ages of 54 and 100 were asked to
identify a dozen familiar smells: onion, lemon, cinnamon, black
pepper, chocolate, rose, banana, pineapple, soap, paint thinner,
gasoline and smoke.

For each mystery scent, they heard and saw a choice of four answers.
For cinnamon, they were asked aloud: "Fruit? Cinnamon? Woody? Or
coconut?" while also seeing the choices in text.

A quarter of the people correctly identified all the odors or missed
only one. Half of them knew at least nine of the 12. The lowest-
scoring quarter of the people correctly identified eight or fewer of
the odors.

The subjects took 21 cognitive tests annually over the next five
years. About one-third of the people developed at least mild trouble
with memory and thinking.

The people who made at least four errors on the odor test were 50
percent more likely to develop problems than people who made no more
than one error. Difficulty identifying odors also was associated with
a higher risk of progressing from mild cognitive impairment to
Alzheimer's.

The researchers took into account age, gender, education and a history
of strokes or smoking, and still found lower scores predicted higher
risk of cognitive decline.

Lead author Robert Wilson of Chicago's Rush University Medical Center
said a diminishing sense of smell isn't cause for panic.

"Not all low scorers went on to have cognitive problems," Wilson said.

Older people should report a loss in smell to their doctors, said
Claire Murphy, an Alzheimer's researcher at San Diego State University
who was not involved in the new study. The problem could be caused by
a polyp in the nose or infected sinuses, she said.

"If a person is old and has a very good sense of smell, that's a very
good sign," Murphy said.

The study was funded by the National Institute on Aging and the
Illinois Department of Public Health.