you smell the roses? Lilacs in spring rain? The alarming odors of
things burning or rotting? The answer may be more important than you
think. Scientists are discovering that an impaired sense of smell is one
of the earliest signs of Alzheimer's and Parkinson's and other
Quality Standards Subcommittee of the American Academy of Neurology has
endorsed smell testing as an aid to the diagnoses of these diseases,
writes Richard L. Doty, though such testing is still not routinely performed in neurology clinics. In an article in The Scientist, Doty, director of the Smell and Taste Center
at the University of Pennsylvania's Perelman School of Medicine,
describes recent research that shows difficulty smelling - a condition
called hyposmia - is often an important early warning signal. He cites a pioneering study
by Amy Bornstein Graves and colleagues at the University of South
Florida who administered smell tests to 1,604 senior citizens who had no
symptoms of dementia. Overall, people who had no sense of smell
and one genetic risk factor for dementia were five times more likely to
develop cognitive decline in the next two years than people whose sense
of smell was not impaired. Further, Doty notes, the smell test was more
predictive than cognitive test scores.
who has developed smell and taste tests, writes that olfactory test
results can help doctors with diagnosis and treatment. Alzheimer's and
Parkinson's diseases (AD and PD) are often misdiagnosed in patients
suffering from other afflictions, including severe depression or supranuclear palsy,
which are not accompanied by loss of smell and are not helped by drugs
used to treat AD and PD. In some patients with mild AD, he adds, smell
tests can indicate responsiveness to a drug that does improve cognitive
function in some patients.
olfactory dysfunction the result of damage that comes with
neurodegenerative diseases, or does loss of smell precede the damage?
Can damage to the olfactory system induce disease in those disposed to
neurodegenerative disorders? Doty says further research is needed to
answer those questions, and further an understanding of the relationship
between smell and health. Watch Doty's slide presentation on the sense of smell. He begins it with a picture of a Lady and the Unicorn tapestry showing the lady weaving a garland of carnations to illustrate the sense of smell. Five of the fifteenth century tapestries depict the five senses and a sixth is believe to represent love or understanding.
Doty's article is one of several in The Scientist issue devoted to examining our sense of smell. Another by Ron Yu discusses pheromones.
These elusive molecules, and the scents associated with them, are known
to influence mating and other behavior in insects and some mammals.
When it comes to human behavior, there's disagreement. If pheromones do
exist in humans, the molecular machinery that would make them work is
not clear. There is also evidence that smells can leave afterimages in the brain, even after the stimulus is no longer present, that influence memory. Marcel Proust, remembering the madeleines of his childhood, wrote that tastes and smells of the past "remain poised a long time, like souls, ..."
"Smell is a potent wizard that transports you across thousands of miles and all the years you have lived." Helen Keller