Loss of Sense of Smell May Help Identify Alzheimer’s

New research suggests odor identification tests may help scientists track the evolution of Alzheimer’s disease in persons at risk.

“Despite all the research in the area, no effective treatment has yet been found for AD,” said 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.

Brietner is one of the authors of a new study on the subject that appears in the journal Neurology.

Loss of memory usually means that the damage to your brain associated with Alzheimer’s disease (AD) may already have been going on for as long as 20 years. Early detection of AD can have profound advantages.

“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,” Brietner said.

Researchers assessed 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 disease. Participants were presented 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 odors 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,” said 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 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 odors) are among the first brain structures first to be affected by the disease.”

The new approach offers a cheaper way to track progression of Alzheimer’s 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.”

“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.

Source: McGill University