Scientists say that a sudden loss of smell, a common sign of Covid, could also be an early sign of a memory-robbing disorder, dementia.
Prior studies had already linked the memory-losing disorder to a slow loss of the ability to smell.
However, recent research shows that a rapid decline can be a better predictor of the condition.
Over 500 senior citizens were under the observation of US experts for over 20 years.
When compared to those who lost their sense of smell over decades, individuals who suffered anosmia over a few years had a nearly twofold increased risk of developing Alzheimer’s.
It “provides another clue,” according to senior research author Professor Jayant Pinto of the University of Chicago, about the link between smell and dementia.
He said that older people should get smell tests as often as they get hearing and vision tests to check for the disease.
Despite being often seen as being less significant than sight and hearing, the sense of smell gives the brain essential information.
Researchers have long recognized a connection between sense and cognitive decline, and memory plays a crucial role in one’s ability to recognize smells.
According to studies, the olfactory and memory-related regions of the brain are often the first to experience the ‘tangles’ of protein amyloid that are a telltale indicator of dementia.
But it’s still not clear if this damage is really what makes a person’s sense of smell get worse.
Professor Pinto and his team wanted to find out if these changes had anything to do with how people lose their sense of smell and brain function as they age.
“Our idea was that people with a rapidly declining sense of smell over time would be in worse shape — and more likely to have brain problems and even Alzheimer’s itself — than people who were slowly declining or maintaining a normal sense of smell,” explains lead author and university researcher Rachel Pacyna.
Twenty years were spent observing 515 individuals in their seventies who did not originally have dementia or cognitive difficulties.
All of the volunteers lived in retirement homes and were tested every year to see how well they could recognize smells and signs of dementia. Some also had MRI scans.
The scores they got on the olfactory tests, which were then put on a graph, showed how much their sense of smell was getting worse. The slope’s downhill tendency was described as “severe,” “decreased,” “unchanged,” or “improved.”
About 100 people in the group later received a dementia or cognitive impairment diagnosis.
Those who lost their sense of smell quickly but didn’t have any typical Alzheimer’s symptoms were 89% more likely to get the memory-robbing disease than those who lost their sense of smell slowly.
People who lost their sense of smell quickly were also more likely to have less grey matter in parts of the brain that control smell and memory, compared to people whose sense of smell went away more slowly.
The changes were most clear in the amygdala and entorhinal cortex, which are parts of the brain that help us smell.
Their risk was the same as that of people with the APOE-e4 gene, which is known to make people more likely to get Alzheimer’s.
People with this gene are three times more likely to get Alzheimer’s than people without it.
The researchers hope to add to their findings by doing autopsies on the volunteers in the future. Autopsies are the gold standard for figuring out if a person has Alzheimer’s.
And they want to try out smell tests in clinics for older people, like eye and hearing tests, to look for early signs of dementia and keep track of them. GOOD
They said that smelling a number of sticks that resembled felt-tip pens was simple, quick, and inexpensive.
Each stick has a unique smell that contestants must choose out of four options.
“If we could identify people in their 40s, 50s and 60s who are at higher risk early on,” adds Ms. Pacyna, “we could potentially have enough information to enroll them into clinical trials and develop better medications.”
The researchers highlighted that just a fifth of patients got MRI scans, and those who did had only one, thus they lacked information on the timing of the onset of structural alterations in the brain.
And most of the volunteers were white, so more research is needed to see if other groups are also affected in the same way.
One of the three main signs of Covid that health officials first noticed when the virus spread around the world last year was a loss or change in the ability to smell or taste.
But as the virus has changed and new strains have spread, many people who have it no longer say that their senses have changed.
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