As researchers strive to discover ways to detect the signs of cognitive decline earlier and earlier, some scientists are looking harder at what the nose knows.
A McGill University study published in Neurology journal used scratch-and-sniff tests to gauge people’s ability to identify strong scents such as lemon, gasoline and bubblegum. Nearly 275 people, average age of 63, took part in the study. Of the participants, 101 also volunteered to provide regular spinal cord fluid samples to track the amount of proteins related to the development of Alzheimer’s disease.
The participants who had increased proteins and other biological indicators of Alzheimer’s also had the most trouble identifying smells accurately.
“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 McGill doctoral student and the first author on the study, in a university release. “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 scents) are among the first brain structures first to be affected by the disease.”
The University of Pennsylvania Smell Identification Test, which was used in the McGill study, has been used in other research to gauge the severity level of Alzheimer’s and to diagnose Parkinson’s disease.
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