Peanut butter sniff test may detect Alzheimer's onset

A tablespoon of peanut butter and a ruler may help confirm a diagnosis of early-stage Alzheimer's disease, according to a study from researchers at the University of Florida.

Graduate students in Florida's McKnight Brain Institute Center for Smell and Taste reported the findings of a small pilot study this week.

Jennifer Stamps, one of the students, came up with the idea of using peanut butter to test for smell sensitivity while working under Dr. Kenneth Heilman, professor of neurology and health psychology.

Stamps noticed while shadowing in Heilman's clinic that patients were not tested for their sense of smell. Olfactory abilities are one of the first things to be affected in cognitive decline.

“Dr. Heilman said, ‘If you can come up with something quick and inexpensive, we can do it,’” Stamps said.

Stamps chose peanut butter, because it is a "pure odorant" that is easily accessible and only detected by the olfactory nerve.

The study had patients sit down with a clinician with about a tablespoon of peanut butter and a metric ruler. Then, the patient closed his or her eyes and mouth and blocked one nostril.

The clinician opened the peanut butter and held the ruler next to the open nostril while the patient breathed normally. The clinician then moved the peanut butter closer and closer to the nose, one centimeter at a time, until the person could detect the scent.

The distance was recorded, and then clinicians did the same on the other nostril. Those clinicians did not know the patients' diagnoses.

Scientists found that in the early stages of Alzheimer's disease, patients had a dramatic difference in detecting odor between the left and right nostril. The left nostril was impaired in patients that had Alzheimer's, and did not detect the smell until it was, on average, 10 centimeters closer to the nose than when testing the right nostril.

This was not the case when testing patients with other types of dementia.

“At the moment, we can use this test to confirm diagnosis,” Stamps said. “But we plan to study patients with mild cognitive impairment to see if this test might be used to predict which patients are going to get Alzheimer’s disease.”

More studies will have to be conducted to fully understand the implications, but should this test or something like it prove successful, it will provide access to the diagnosis in areas not equipped with new technology.

“We see people with all kinds of memory disorders,” Heilman said. Many tests to confirm a diagnosis of Alzheimer’s disease or other dementias can be time-consuming, costly or invasive. “This can become an important part of the evaluation process.”