Could olfactory loss point to Alzheimer's disease?

August 16, 2017
Credit: McGill University

By the time you start losing your memory, it's almost too late. That's because the damage to your brain associated with Alzheimer's disease (AD) may already have been going on for as long as twenty years. Which is why there is so much scientific interest in finding ways to detect the presence of the disease early on. Scientists now believe that simple odour identification tests may help track the progression of the disease before symptoms actually appear, particularly among those at risk.

"Despite all the research in the area, no effective treatment has yet been found for AD," says Dr. John Breitner, the director of the Centre for Studies on Prevention of Alzheimer's Disease at the Douglas Mental Health Research Centre of McGill University. He is one of the authors of the study on the subject that was recently published in the journal Neurology. "But, 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%."

Bubble gum or gasoline?

Close to 300 people with an average age of 63 who are at risk of developing AD because they had a parent who had suffered from the , were asked to take multiple choice scratch-and-sniff tests to identify scents as varied as bubble gum, gasoline or the smell of a lemon. One hundred of them also volunteered to have regular lumbar punctures to measure the quantities of various AD-related proteins whose presence in the cerebrospinal fluid (CSF).

The researchers found that those with the most difficulty in identifying odours were those in whom other, purely biological indicators of AD, were most evident.

"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," says Marie-Elyse Lafaille-Magnan, a doctoral student at McGill and the first author on the study. "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 that are currently being used," the director of research program on Aging, Cognition and Alzheimer's disease of the Douglas Institute and one of the authors on the study. "However, problems identifying smells may be indicative of other medical conditions apart from AD and so should not be substituted for the current tests."

The researchers caution more that far more work needs to be done to see how changes in a person's ability to identify smells over time relates to the progression of the disease itself. For the time being, smell tests are simply one more avenue to explore as researchers look for ways to identify the disease before the symptoms actually begin to appear.

"Odor identification as a biomarker of preclinical AD in older adults at risk," was published in Neurology.

Explore further: Detecting Alzheimer's disease before symptoms emerge

More information: Odor identification as a biomarker of preclinical AD in older adults at risk. Neurology. July 25, 2017 doi: dx.doi.org/10.1212/WNL.0000000000004159

Related Stories

Detecting Alzheimer's disease before symptoms emerge

May 31, 2017
Long before symptoms of Alzheimer's disease become apparent to patients and their families, biological changes are occurring within the brain. Amyloid plaques, which are clusters of protein fragments, along with tangles of ...

Sleep problems may be early sign of Alzheimer's

July 5, 2017
Poor sleep may be a sign that people who are otherwise healthy may be more at risk of developing Alzheimer's disease later in life than people who do not have sleep problems, according to a study published in the July 5, ...

Failing sense of smell might be Alzheimer's warning

November 16, 2015
(HealthDay)—Losing your sense of smell may mark the start of memory problems and possibly Alzheimer's disease, a new study suggests.

Study confirms 'sniff test' may be useful in diagnosing early Alzheimer's disease

December 20, 2016
Tests that measure the sense of smell may soon become common in neurologists' offices. Scientists have been finding increasing evidence that the sense of smell declines sharply in the early stages of Alzheimer's, and now ...

Ability to recognize and recall odors may identify those at risk for Alzheimer's disease

November 14, 2016
A non-invasive protocol testing the ability to recognize, remember and distinguish between odors was able to identify older individuals who - according to genetic, imaging and more detailed memory tests - were at increased ...

Poor odor identification may be early warning for dementia

February 3, 2017
Poor performance on a simple odor identification test was associated with a significantly increased risk of developing dementia years later, in a study of more than 2,400 older black and white adults led by Kristine Yaffe, ...

Recommended for you

Personality changes don't precede clinical onset of Alzheimer's, study shows

September 21, 2017
For years, scientists and physicians have been debating whether personality and behavior changes might appear prior to the onset of Alzheimer's disease and related dementias.

Newly ID'd role of major Alzheimer's gene suggests possible therapeutic target

September 20, 2017
Nearly a quarter century ago, a genetic variant known as ApoE4 was identified as a major risk factor for Alzheimer's disease—one that increases a person's chances of developing the neurodegenerative disease by up to 12 ...

Is the Alzheimer's gene the ring leader or the sidekick?

September 15, 2017
The notorious genetic marker of Alzheimer's disease and other forms of dementia, ApoE4, may not be a lone wolf.

Potential noninvasive test for Alzheimer's disease

September 6, 2017
In the largest and most conclusive study of its kind, researchers have analysed blood samples to create a novel and non-invasive way of helping to diagnose Alzheimer's disease and distinguishing between different types of ...

Researchers unlock the molecular origins of Alzheimer's disease

September 6, 2017
A "twist of fate" that is minuscule even on the molecular level may cause the development of Alzheimer's disease, VCU researchers have found.

Is dementia declining among older Americans?

September 5, 2017
(HealthDay)—Here's some good news for America's seniors: The rates of Alzheimer's and other forms of dementia have dropped significantly over the last decade or so, a new study shows.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.