Jennifer Stamps, a graduate student at the University of Florida McKnight Brain Institute Center for Smell and Taste, had noticed during research that patients were being not tested for their sense of smell. The ability to smell is associated with the first cranial nerve and is usually one of the first things to be affected in cognitive decline — a key component of Alzheimer’s disease.
Stamps chose peanut butter because, she said, it is a “pure odorant” that is only detected by the olfactory nerve and is easy to acquire.
During the study, participants were asked to close their eyes, mouth, and block one nostril. The clinician then opened the peanut butter jar and held the ruler next to the open nostril as the participant breathed normally.
The clinician then moved the peanut butter up the ruler one centimeter at a time until the participant could detect an odor. The distance was recorded and the method was repeated on the other nostril after 90 seconds had passed.
The clinicians who conducted the test were not aware of the patients’ diagnoses, which were not usually confirmed until weeks after the first clinical test.
The scientists found that patients in the early stages of Alzheimer’s disease had a dramatic difference in their ability to detect smells between the left and right nostril—the left nostril was dysfunctional and did not detect the smell until it was an average of 10 centimeters closer to the nose than the right nostril.
In patients with other kinds of dementia, this was not the case; instead, these patients had either no differences in odor detection between nostrils or the right nostril was worse at detecting odor than the left nostril.
Of the 24 patients tested who had mild cognitive impairment, about 10 showed a left nostril impairment and 14 patients did not. The researchers said more studies must be conducted to fully understand what this means.
“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.”
The researchers add that this test could be used by clinics that are unable to conduct other more elaborate tests required for a specific diagnosis. At UF Health, the peanut butter test will be one more tool to add to a full suite of clinical tests for neurological function in patients with memory dysfunction.
In people with Alzheimer’s, one of the first places in the brain to break down is the front part of the temporal lobe that evolved from the smell system, and this region of the brain is involved in forming new memories.
“We see people with all kinds of memory disorders,” said UF neurologist Kenneth Heilman, M.D. 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.”
Source: University of Florida