Poor sense of smell could be indicator of Alzheimer’s disease, finds new study

There are currently 850,000 people with dementia in the UK

Sarah Young
Monday 21 August 2017 11:47 BST
(Getty Images)

Scientists have highlighted a little-known symptom of Alzheimer’s disease which could help supply earlier diagnosis in patients.

While it is thought that initial damage to the brain from dementia occurs up to 20 years before any symptoms appear, there are currently no tests to confirm whether or not this is happening.

But now, scientists at McGill University in Quebec believe they have found a possible link that connects loss of smell to early indication of the disease.

Testing the theory on 300 participants who were at high risk of developing Alzheimer’s disease because they had a parent who suffered from it, each person was asked to take a multiple choice scratch-and-sniff test.

While all were asked to identity strong scents such as bubblegum, petrol and lemon, 100 of them also volunteered to have regular lumbar punctures to measure proteins related to the disease in their spinal fluid.

The researchers found that those who had the most difficulty identifying odours were also those who had the most biological indications of Alzheimer’s disease.

“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,” said Marie-Elyse Lafaille-Magnan, first author of the study, in a statement.

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

“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.”

Although there are currently no treatments for Alzheimer’s disease, experts say that this smell test could be used to track the disease before other symptoms appear and even reduce the symptoms one they begin.

“If we can delay the onset of symptoms by just five years, we should be able to reduce the prevalence and severity of these symptoms by more than 50 percent,” Dr. John Breitner, the director of the Centre for Studies on Prevention of Alzheimer's Disease at McGill University, said.

While the researchers are hopeful, they recognise that more tests need to be performed and that, for now, smell alone should not be used to diagnose the disease.

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