If you’re worried about getting Alzheimer’s disease, a simple DIY test could help confirm or quell your fears. 

Scientists at the University of Florida (UF) emphasize that a reduced ability to smell can serve as an early indicator of Alzheimer’s disease. This is because damage to brain areas associated with scent detection can happen before common cognitive symptoms such as memory problems or disorientation become evident.

With this in mind, they developed a test that anyone can perform at home using a dollop of peanut butter and a ruler.

Jennifer Stamps, who was a graduate student at the UF McKnight Brain Institute Center for Smell and Taste during the research, noted that peanut butter was used due to its nature as a ‘pure odorant.’

A ‘pure odorant’ is a term for a substance that solely triggers the sense of smell without stimulating the trigeminal nerve, which is linked to experiences of touch, pain, and heat.

Other examples of pure odorants include anise, banana, mint and pine.

This UF study, initially conducted in 2013 but recently brought back into focus, involved patients visiting the clinic for tests. They participated alongside a clinician, equipped with a jar of peanut butter and a metric ruler.

The patient closed his or her eyes and mouth and blocked one nostril. 

Experts at the University of Florida (UF) argue that a diminished sense of smell serves as an early indication of Alzheimer’s, given that brain regions tied to scent recognition may suffer damage before other cognitive symptoms emerge (stock image).

The clinician positioned the peanut butter at a measured distance from the patient’s open nostril, marking with the ruler the exact point at which the patient reported detecting the scent.

The distance was recorded and the procedure was repeated on the other nostril after a 90-second delay.

The clinicians running the test did not know the patients’ diagnoses, which were not usually confirmed until weeks after the initial clinical testing.

The scientists found that patients in the early stages of Alzheimer’s disease had a dramatic difference between the left and right nostril in detecting odor. 

The left nostril in these patients did not detect the smell until it was an average of 10 centimeters closer to the nose compared to the right nostril.

This was not the case in patients with other kinds of dementia. Instead, these patients had either no differences in odor detection between nostrils, or the right nostril was worse at detecting odor than the left.

Of the 24 patients tested who had mild cognitive impairment, which can turn into Alzheimer’s disease, 10 showed a left nostril impairment. 

The researchers said more studies must be conducted to fully understand the implications.

The prevalence of Alzheimer’s disease shown in 50 US states and 3,142 counties in 2023

The above chart was created from data from Rajan et al. The percentages do not total 100 due to rounding

Dr. David Sinclair, a professor of genetics at Harvard Medical School who was not involved in the study, told the Daily Mail that he believes the peanut butter and ruler test is a ‘simple and inexpensive yet effective’ way of testing for early-stage Alzheimer’s disease.

Alzheimer’s progresses over time, with each stage lasting a different duration. It can take about two years for the early stage to progress into the middle stage, or at least eight to 10 years from diagnosis to the late stages of the disease. 

In the earliest stages, a poor sense of smell is often one of the first signs.

‘Alzheimer’s disease often affects brain hemispheres unequally and possibly the olfactory bulbs (the first structures in the brain to process smells) too,’ Dr. Sinclair explained.

‘In turn, this can mean that one nostril can become less sensitive to smell than the other.’

The use of peanut butter might prove problematic for patients with nut allergies, but Dr. Sinclair noted that a different substance can be used.

‘In the future, there might be standardized Alzheimer’s tests that mimic this one, using a specific quantity of a stable, non-allergenic odorant,’ he explained. 

Dr. Gayatri Devi, a clinical professor of neurology at the Zucker School of Medicine at Hofstra/Northwell in New York who was not involved with the study, told the Daily Mail that alternatives to could include banana, chocolate, cinnamon, lemon and onion.

This year, researchers from Mass General Brigham in Boston developed olfactory tests in which participants sniff odor labels that have been placed on a card to assess their ability to discriminate, identify and remember odors. 

They found that participants could successfully take the test at home and that older adults with cognitive impairment scored lower on the test than cognitively normal adults. 

The UF researchers said these types of tests could be used by clinics that don’t have access to the personnel or equipment to run more elaborate tests required for a specific diagnosis.

However, Dr. Devi said the scent tests should not be done at home and should be performed ‘within the proper context of a medical examination, as it was for the study.’

‘In this age, when everyone is concerned about brain health and about developing a dementia, we don’t want these people to get worried and stressed because they can’t smell,’ she said.

‘DIY tests to diagnose Alzheimer’s are not recommended given the gravity of such a diagnosis and should really only be done in proper context.’ 

Alzheimer’s disease is one of the most common forms of dementia and mostly affects adults over the age of 65.

It is believed to be caused by the development of toxic amyloid and beta proteins in the brain, which can accumulate and damage cells responsible for memory.

Amyloid protein molecules stick together in brain cells, forming clumps called plaques, while tau proteins twist together in fiber-like strands called tangles. 

The plaques and tangles block the ability of the brain’s neurons to send electrical and chemical signals back and forth. 

Over time, this disruption causes permanent damage in the brain that leads to Alzheimer’s disease and dementia, causing patients to lose their ability to speak, care for themselves or even respond to the world around them.

About 7million people in the US 65 and older live with the condition, and over 100,000 die from it annually. 

The Alzheimer’s Association estimates that by 2050, nearly 13 million Americans will be living with the disease.