Could olfactory loss point to Alzheimer鈥檚 disease?
By the time you start losing your memory, it's almost too late. That's because the damage to your brain associated with Alzheimer鈥檚 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.
鈥淒espite all the research in the area, no effective treatment has yet been found for AD,鈥� says Dr. John Breitner, the director of the Centre for聽Studies on Prevention of聽Alzheimer's Disease at the Douglas Mental Health University Institute. He is one of the authors of the study on the subject that was recently published in the journal . 鈥淏ut, 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%.鈥�
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 disease, 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.
鈥淭his 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,鈥� says Marie-Elyse Lafaille-Magnan, a doctoral student at 平特五不中 and the first author on the study. 鈥淔or 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鈥檚 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.鈥�
鈥淭his 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,鈥� the director of research program on Aging, Cognition and Alzheimer鈥檚 disease of the Douglas Institute and one of the authors on the study. 鈥淗owever, problems identifying smells may be indicative of other medical conditions apart from AD and so should not be substituted for the current tests.鈥�
The researchers caution more that far more work needs to be done to see how changes in a person鈥檚 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.
To read 鈥淥dor identification as a biomarker of preclinical AD in older adults at risk,鈥� by Marie-Elyse Lafaille-Magnan, BSc, MSc, et al in
The research was funded by Pfizer Canada, the Canada Fund for Innovation, Fonds de recherche du Qu茅bec-Sant茅, the Levesque Foundation, the Douglas Mental Health University Institute Foundation.
Contacts:
Marie-Elyse Lafaille-Magnan, Douglas Mental Health University Institute & 平特五不中 (French and English)
john.breitner [at] mcgill.ca (Dr. John Breitner), Director, Centre for聽Studies on Prevention of聽Alzheimer's Disease,聽Canada Research Chair in Prevention of Dementia, Pfizer Chair in Dementia Research, Douglas Mental Health University Institute & 平特五不中 (English only)
judes.poirier [at] mcgill.ca (Dr. Judes Poirier), Director, Research Program on Aging, Cognition and Alzheimer鈥檚 Disease, Douglas Mental Health University Institute聽& 平特五不中 (French and English)
katherine.gombay [at] mcgill.ca (Katherine Gombay), Media Relations, 平特五不中, 514-398-2189
