Odor test may help predict Alzheimer’s disease

A simple odor identification test might help doctors more accurately predict which individuals with mild cognitive impairment will go on to develop Alzheimer’s disease, according to new research published in the September issue of the American Journal of Psychiatry.

In the study, D.P. Devanand, M.D., and colleagues at Columbia Presbyterian Medical Center in New York asked 90 men and women who had minor memory problems and other mild cognitive impairments to participate in a 15 to 20 minute “scratch and sniff” test.

The participants, whose mean age was 67, were exposed to 40 distinct smells such as menthol, peanuts and soap. Each odor was embedded in a microcapsule on a separate page. After scratching open the capsule and smelling its contents, each participant was asked to identify the odor from four alternatives listed for each capsule.

None of the 30 individuals who scored well on the test developed Alzheimer’s disease during the follow-up period, which averaged 20 months. But the researchers found 19 of 47 people with mild cognitive impairment who had difficulty identifying these smells or odors went on to develop Alzheimer’s disease during the follow-up period. Of those 19, 16 reported that they had a good sense of smell at the time of the test, yet scored poorly on it.

This finding suggests that the inability to recognize smells, when combined with a lack of awareness that olfactory senses are impaired, might be used as a predictor of impending Alzheimer’s disease. Thirteen of the 90 participants in this study had not completed follow-up at the time of publication.

If these findings are independently replicated in larger patient samples, odor identification potentially may be used to estimate who is at risk to develop Alzheimer’s disease, according to Elisabeth Koss, Ph.D., assistant director of the Alzheimer’s Disease Center Program at the National Institute on Aging.

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