Study says loss of smell may help sniff out Alzheimer’s disease

A small pilot study of patients displaying signs of cognitive decline found that peanut butter can help identify those with Alzheimer’s disease, which is often accompanied by a loss of smell.

The results indicate that loss in sense of smell may help in diagnosing Alzheimer’s. Loss of smell can be detected long before classic clinical symptoms, and it may not only be an early warning sign of Alzheimer’s, but it is also an indicator for Parkinson’s disease and some other neurological disorders, writes Richard Doty of the Smell and Taste Center at the University of Pennsylvania’s Perelman School of Medicine.

Alzheimer’s is an irreversible, progressive brain disease that slowly destroys memory and thinking skills, but early diagnosis is usually beneficial. It can tell people whether their symptoms are from Alzheimer’s or another cause, such as stroke, tumor, Parkinson’s or other conditions that may be treatable. In most people with Alzheimer’s, symptoms first appear after age 60, and estimates suggest that as many as 5.1 million Americans may have it, says the National Institute on Aging.

The study of 96 patients was conducted by the McKnight Brain Institute Center for Smell and Taste at the University of Florida. Eighteen of the patients had probable Alzheimer’s, 24 had a mild cognitive impairment, 26 had some form of dementia, and the other 26 patients were used as a control group.

The researchers measured the distance from the nose at which patients, whose eyes were closed, could smell a tablespoon of peanut butter one nostril at a time. Early-stage Alzheimer’s patients had different smell sensitivity between the right and left nostrils, with the left regularly being more severely impaired. The other patients displayed no such difference in smell sensitivity, says the study, published in the Journal of Neurological Sciences.

“This non-invasive and inexpensive left–right nostril odor detection test appears to be a sensitive and specific test for probable Alzheimer’s disease,” graduate student Jennifer Stamp, one of the researchers, told Jef Akst of The Scientist magazine. More research is needed to validate the approach, she added: “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.”

Click here to read Doty’s “Smell and the Degenerating Brain” for a deeper look at the link between smell and neurodegeneration. Click here for more information about Alzheimer’s disease.