Peanut Butter: Diagnosing Alzheimer’s in a Jif?

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The news outlets have been buzzing with the results of a clinical test conducted at the University of Florida that has the potential of confirming a diagnosis of Alzheimer’s disease through smelling peanut butter. Is this a joke or is there evidence to support this claim?

The trial is based on the fact that Alzheimer’s disease initially affects the front temporal lobe of the brain. This area controls information processing, including sensory information. There have been a number of studies over the past 10 years that have confirmed that individuals with Alzheimer’s disease have a reduced ability to detect smells. One premise of this study is that the left side of the brain is more impaired by Alzheimer’s than the right side of the brain. There does not seem to be much research on whether the senses on the left side of the body are more impaired than those on the right side. However, if true,  people with Alzheimer’s disease might have more olfactory impairment in the left nostril than the right nostril.

The University of Florida designed a study to see if it could develop a simple test to confirm whether an individual with cognitive impairment has Alzheimer’s disease. The study involved 94 subjects, 18 with Alzheimer’s, 24 with mild cognitive impairment, 26 with dementia caused by other factors, and 26 matched controls. The subjects (other than the controls) were patients at a UF clinic and which tests for Alzheimer’s. At the time of the experiment, the investigators did not know the diagnoses for the subjects.

The graduate student conducting the experiment used a metric ruler and a tablespoon of peanut butter. She asked the subject to close one nostril and their eyes. She started off placing the peanut butter 30 cm away from the open nostril. Moving the peanut butter up by 1 cm increments, the investigator noted the distance at which the subject could smell the peanut butter. After a break of 90 seconds, the experiment was repeated on the other nostril.

The results showed that those diagnosed with Alzheimer’s disease could smell the peanut butter with their right nostril 10 cm further away than with their left nostril. The data indicates that the outcomes were statistically significant. Does this mean that we should all whip out our jars of Jif, grab a ruler, and make a self-diagnosis?

Probably not.  First, the sample size in this trial was very small. It is not clear how the investigator controlled for things like random air currents, conditioning of the subject once they knew they were supposed to be smelling peanut butter, and pre-existing conditions, such as colds and sinus problems.

On the other hand, if the experiment can be repeated with larger populations and controlled for confounders, it might be an effective sensory screen for people who are at the early stages of the disease.

Jennifer Stamps, the graduate student who conducted the test, is quoted as saying that if clinicians can make a diagnosis early “we can start treatment more aggressively at the early stage and you can possibly prevent a lot of progression”. As the Alzheimer’s Association and numerous researchers have repeatedly stated, there is currently no effective treatment for Alzheimer’s disease, and therefore this test, like the PET scans, even if found to be accurate, does not currently lead to better outcomes. However, should treatments be found that effectively delay or slow the progression of this disease, peanut butter may have a role to play in improving outcomes.

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