A simple smell-test between the odours of bubble gum or gasoline could potentially be a telltale sign of Alzheimer’s disease progression.
Researchers from the McGill University recruited 274 participants who were considered to be ageing healthily at the beginning of the trial, but had a parental or multiple-sibling history of Alzheimer’s disease.
All participants were asked to undertake what was called ‘scratch-and-sniff tests’, used to identify scents such as bubble gum, gasoline or the smell of a lemon. The researchers also collected cerebrospinal fluid from 100 of the participants to assess quantities of various Alzheimer’s disease-related toxic proteins.
The results, published in the journal Neurology, found that reduced odour identification was associated with a lower cognitive score and older age, as well as increased ratios of a number of Alzheimer’s disease toxic proteins such as amyloid beta and Tau.
Marie-Elyse Lafaille-Magnan, a PhD student at McGill University who led the study, said this is the first time that anyone has been able to show clearly that loss of the ability to identify smells is correlated with toxic markers indicating advancement 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,” Ms Lafaille-Magnan said.
“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 the naming of odours) are among the first brain structures to be affected by the disease.”
Although this study is interesting, researchers do stress that far more research is now needed to see how changes in a person’s ability to identify smells over time relates to the progression of the disease itself.
They also note that a smell-test would only ever be indicative and do not believe it would ever replace other diagnostic means, but could be included as part of a battery assessment.
More research is now being undertaken in this area to further refine a smell-test as part of an Alzheimer’s disease assessment.
You can learn more about the research here