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Canadian study finds loss of smell could be dementia sign

 
  • An inability to identify aromas signal the build-up of toxic proteins in the brain
  • High levels of such clumps in the brain are a hallmark of the devastating disease
  • The groundbreaking study could lead to a smell test for early signs of dementia 

Stephen Matthews For Mailonline

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Struggling to differentiate between the smell of bubble gum and petrol could be a sign of dementia, if new research is to be believed.

Changes in the ability to identify aromas signal the build-up of toxic proteins in the brain – a hallmark of the devastating disease.

The groundbreaking findings could lead to a smell test for early signs of dementia, an idea which has long been touted by researchers.

Currently the disease can go unnoticed for up to 20 years, with no accurate ways to spot the irreversible damage in existence yet – despite years of research. 

Canadian researchers said testing for the deterioration of smell, known to occur in the early stages of dementia, could delay the onset of memory loss.

Changes in the ability to identify aromas, such as petrol, signal the build-up of toxic proteins in the brain - a hallmark of the devastating disease, scientists claim

Changes in the ability to identify aromas, such as petrol, signal the build-up of toxic proteins in the brain - a hallmark of the devastating disease, scientists claim

Changes in the ability to identify aromas, such as petrol, signal the build-up of toxic proteins in the brain – a hallmark of the devastating disease, scientists claim

McGill University researchers claim the first sign of damage could be to the olfactory neurons, which help to distinguish between different odours.

Other ideas touted include the build-up of toxic proteins in the brain affect memory – explaining why people are unable to recognise certain smells. 

How was the study carried out? 

The new findings, published in the journal Neurology, were based on nearly 300 people at risk of developing Alzheimer’s disease – the most common form of dementia.

Participants were asked to take scratch-and-sniff tests to identify scents. The odours were bubble gum, gasoline and lemon.  

One hundred of them also volunteered to have regular lumbar punctures to measure the quantities of various dementia-related proteins in their cerebrospinal fluid.

The researchers found those with the most difficulty in identifying odours were those whose biological indicators of Alzheimer’s were most evident.

DEMENTIA ‘SMELL TEST’

A test for people who lose their sense of smell in the early stages of Alzheimer’s could diagnose the condition before it strikes, it was reported in January.

Massachusetts General Hospital and Harvard Medical School scientists developed a simple scan which may be able to pinpoint dementia before memory loss even begins.

The key is in someone’s sense of smell, which starts to deteriorate in many neurological conditions, from Down’s syndrome and schizophrenia to Alzheimer’s and Parkinson’s disease.

It is why there is a so-called ‘peanut butter test’ for people with Alzheimer’s who are less able to sniff out the spread from a distance.

However simple smell tests offer an incomplete picture, monitoring the sense of smell only after it is detected by the brain.

The researchers developed a PET scan, called Neuroflux, which avoids the need for a painful biopsy, and picks up the early signs of Alzheimer’s in the nose. 

The first study of its kind 

Lead author Marie-Elyse Lafaille-Magnan said: ‘This is the first time that anyone has been able to show clearly that the loss of the ability to identify smells is correlated with biological markers indicating the advance of the disease.

‘For more than 30 years, scientists have been exploring the connection between memory loss and the difficulty that patients may have in identifying different odours. 

‘This makes sense because it’s known that the olfactory bulb (involved with the sense of smell) and the entorhinal cortex (involved with memory and naming of odours) are among the first brain structures first to be affected by the disease.

‘This means that a simple smell test may potentially be able to give us information about the progression of the disease that is similar to the much more invasive and expensive tests of the cerebrospinal fluid that are currently being used.’ 

More research is needed 

But the researchers cautioned more work is needed to understand why a diminishing sense of smell is linked to dementia.

They hinted problems identifying smells can be an indicator of other neurological conditions, including schizophrenia and Parkinson’s.

For the time being, smell tests are one more avenue to explore as they continue their quest to find ways of identifying the disease early.

An estimated 850,000 people in the UK are thought to be living with dementia, with figures expected to rise to one million by 2025, and two million by 2050.

Statistics in the US estimate 5.5 million Americans of all ages to be plagued with Alzheimer’s disease.

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