If You Can't Smell This, It Could Be an Early Sign of Dementia, Study Says
This surprising symptom could help you sniff out a dementia diagnosis.
When most people think of the early signs of dementia, they think of those first instances of recognizable memory loss: missing a medical appointment, forgetting someone's name, misplacing the car keys—or even the car itself. Yet dementia has early symptoms that have nothing to do with memory, which could tip you off to a problem.
According to neuropsychiatrists at Amen Clinics, there are many subtle behavioral and medical changes you may notice before your short term memory starts to suffer, including experiencing certain food cravings, forming compulsive habits, engaging in risky behaviors without inhibition, and falling more frequently. On top of these, you may have a sudden difficulty smelling and distinguishing between certain scents. Read on to learn the simple, at-home test that could pinpoint a problem, and to find out which scents may signal a dementia diagnosis.
According to a 2018 study published in the journal Biosensors, roughly 50 million people suffer from Alzheimer's disease (AD), and instances of the condition are "rising exponentially due to increasing global life expectancy." However, "there is currently no definite diagnosis of AD until after death, thus an early biomarker for AD is urgently required in order to administer timelier and more effective interventions," the study states.
Several studies have found that losing your sense of smell—a phenomenon known as anosmia—is one of the earliest symptoms of Alzheimer's disease. Researchers believe that anosmia occurs in AD patients because "the brain is losing its ability to self-repair."
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One 2017 study published in the Journal of the American Geriatrics Society determined that there is, in fact, a strong link between olfactory decline and dementia. The study's researchers assembled a "nationally representative sample" of 2,906 men and women between the ages of 57 and 85, who completed a short interview and underwent a five-item smell test. Subjects were tasked with identifying five scents—peppermint, fish, orange, rose, and leather—by sniffing "a device similar to a felt-tip pen." They were then provided four possible answers and asked to identify which one they were smelling.
Five years later, the research team conducted a follow-up interview. They found that those who were unable to identify at least 4 out of the 5 odors were more than twice as likely to have developed dementia during that time.
"These results show that the sense of smell is closely connected with brain function and health," said Jayant M. Pinto, MD, a professor of surgery at the University of Chicago in Illinois and senior author of the study. "We think a decline in the ability to smell, specifically, but also sensory function more broadly, may be an important early sign, marking people at greater risk for dementia," he told Medical News Today.
A 2013 experiment published in the Journal of Neurological Science also found that anosmia is linked to dementia. That team assembled 68 patients who had been diagnosed with probable Alzheimer's disease and screened them to determine that they had "no confounding variables for olfactory dysfunction." With a sample of peanut butter placed at a precise distance from their nostrils, participants closed their eyes, mouths, and blocked off one nostril at a time, and attempted to identity the scent.
The researchers found that not only did Alzheimer's patients have a difficult time identifying the scent, they specifically had an olfactory deficit in the left nostril compared with the right. "The AD group demonstrated significantly more asymmetry of odor detection between nostrils than all other groups due to a left nostril impairment," the team explained. "A left nostril impairment of odor detection was present in all the patients with probable AD."
The researchers believe this suggests an impairment in the olfactory cortex in the left hemisphere of the brain, an area responsible for functions like language and calculation.
While anosmia can add a crucial piece to the puzzle of an Alzheimer's diagnosis, there are other possible causes for your impaired sense—especially in the absence of other cognitive symptoms.
Sinus infections, nasal polyps, COVID-19, Parkinson's Disease, allergies, side effects from certain medications, and environmental factors are all known to cause anosmia. If you notice a change in your ability to smell, contacting a doctor is always your safest bet.