Researchers at the University of Florida discovered that an altered sense of smell in the left nostril may be a warning sign of early-stage Alzheimer's.
Researchers at the University of Florida discovered that an altered sense of smell in the left nostril may be a warning sign of early-stage Alzheimer’s.

Researchers at the University of Florida discovered that an altered sense of smell in the left nostril may be a warning sign of early-stage Alzheimer’s. A study was conducted on over 90 participants who were asked to smell a spoonful of peanut butter from a short distance. As per the studies, those with probable Alzheimer’s disease had issues smelling the peanut butter with their left nostril. These researchers had to move the peanut butter container around 10 cm closer to the left nostril than the right nostril for the affected individuals to appreciate the smell.

Some participants of this study had confirmed early-stage Alzheimer’s disease, some were diagnosed with dementia, and others had no current cognitive or neurological problems.

The researchers have reported that only those with a confirmed diagnosis of early-stage Alzheimer’s had trouble smelling the peanut butter. The difference in smell acuity between the left and right nostrils is unique in this disease.

Some brain research studies showed that the shrinking seen in the brain afflicted with Alzheimer’s starts on the left side of the brain. However, this study needs more evidence.

Research indicates that the peanut butter test might single out those with probable Alzheimer’s. Sense of smell is often the first sense to decline in cognitive decline, even before memory loss. However, a similar study conducted by the University of Pennsylvania could not replicate these results.

How is the test performed?

During this test:

  • The clinician will ask the person to close their eyes, mouth, and block one of the nostrils with a thumb over the nares.
  • A ruler will be kept next to the open nostril as the person breathes normally.
  • Then peanut butter will be placed in a small plastic cup up the ruler and will be moved at a time until the person can detect the smell.
  • The distance will be recorded.
  • The same test will be repeated for the other nostril.

Is the study reliable?

The study needs to replicate the results using larger sample sizes to confirm the accuracy of the peanut butter test. Also, with smell impairments being much greater in some other forms of dementia, the test may give variable results and would make the diagnosis difficult. The test, unfortunately, cannot differentiate between different types of dementia.

Other most accurate early-stage diagnostic tests for Alzheimer’s are checking for an amyloid deposit on the positron emission tomography (PET) scan. However, these are more expensive, uncomfortable, and not easily available or accessible everywhere, making the diagnosis and research difficult.

The peanut smell test fulfills the need for inexpensive, accurate, and accessible testing in the early stages of Alzheimer’s to prevent treatment delay and future memory loss, so it helps with selective screening.

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How are the sense of smell and Alzheimer’s interconnected?

There are numerous studies conducted on strengthening the connection between a failing sense of smell and an early warning of Alzheimer’s.

A group of studies conducted in Minnesota discovered that seniors who had the worst smell test score were 2.2 times more likely to show signs of mild cognitive decline. Additionally, the participants were already exhibiting memory problems and obtained low smell test scores. These people are more likely to progress to Alzheimer’s.

Over 1,400 healthy seniors with an average age of 79 years have been studied for three and a half years. Around 250 people developed mild memory programs and 64 people developed dementia.

Six food items and six non-food items were tested on these senior groups. Through the study, researchers noted that as the sense of smell declined, the likelihood of memory problems and Alzheimer’s increased.

The study findings suggest that this peanut butter smell test may help identify the elderly who is likely to develop memory problems. Furthermore, if they already have these problems, it will help understand if the problems will progress to Alzheimer’s or dementia. There could be a problem linked to neurodegenerative disease in Alzheimer’s, but it is too early to use a smell test as a diagnostic tool for Alzheimer’s or dementia.

Alzheimer’s cases are on the rise and currently, there is no cure for this disease. However, large studies are being conducted to identify who may be susceptible to it and the possible treatments and prevention strategies for the progression of the disease.

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Medically Reviewed on 4/16/2021
References
Cleveland Clinic. How a Peanut Butter Test May Detect Alzheimer’s. https://health.clevelandclinic.org/peanut-butter-test-may-detect-alzheimers/

Sauer A. Can’t Smell Peanut Butter? Alzheimer’s May Be the Culprit. Alzheimer’s.Net. January 20, 2016. https://www.alzheimers.net/2014-09-19-peanut-butter-test-predicts-alzheimers