The decline in a person’s sense of smell over time can not only predict loss of cognitive function, but its rapid decline can also predict structural changes in brain regions that are important for Alzheimer’s disease and dementia in general.
That’s the main finding of research by the University of Chicago Medicine that offers “another clue” to how a rapid decline in smell is a “really good” indicator of what will eventually happen. structurally occur in specific regions of the brain, brain, summarizes Jayant M. Pinto, one of its authors.
Based on a follow-up study of 515 older adults, it is published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.
Memory plays a fundamental role in the human ability to recognize smells, and the scientific community has long known of the relationship between smell and dementia, recalls a press release from the University of Chicago.
The plaques and tangles – of proteins – that characterize the tissues affected by Alzheimer’s disease generally appear in the olfactory areas of the brain and those associated with memory before developing in other parts of this organ. However, it is still unclear whether this damage is the cause of a person’s diminished sense of smell.
Pinto and his team wanted to see if it was possible to identify brain alterations correlated with a person’s loss of sense of smell and cognitive function over time.
“Our idea was that people whose sense of smell declines rapidly over time would be in poorer condition — and more likely to have brain problems and even Alzheimer’s disease itself — than those whose sense of smell declines. slowly or is maintained. A normal smell”, details Rachel Pacina.
The team used anonymous patient data from Rush University’s Aging and Memory Project, launched in 1997 to investigate chronic conditions of aging and neurodegenerative diseases, such as Alzheimer’s disease.
Patients undergo annual tests to check their ability to identify certain smells, their cognitive function or signs of dementia; some also had an MRI.
In their observations, the scientists found that a rapid decline in a person’s sense of smell during a period of normal cognition predicts multiple features of Alzheimer’s disease, including decreased gray matter volume in areas of the brain related to smell and memory, lower cognition and an increased risk of dementia.
In fact, the risk of losing your sense of smell was similar to that of carrying the APOE-e4 gene, a known genetic risk factor for developing Alzheimer’s disease.
The changes were most notable in primary olfactory regions, including the amygdala and the entorhinal cortex, which is an important input for the hippocampus, a critical site in Alzheimer’s disease.
“We were able to show that the volume and shape of gray matter in olfactory and memory-associated areas in people with rapid decline in smell was lower compared to those with less severe olfactory decline,” summarizes Pinto.
According to the researcher, this study “must be taken in the context of all known risk factors for Alzheimer’s disease, including the effects of diet and exercise”.
“The sense of smell and its changes should be an important element in the context of a number of factors that we believe affect the brain in health and aging.”
For Pacyna, if people in their 40s, 50s and 60s who are most at risk could be identified early, they might have enough information to enroll them in clinical trials and develop better drugs.
However, the scientists admit some limitations of the study, such as the fact that the participants only had an MRI scan, therefore lacking data to determine when structural changes in the brain began or how quickly the brain regions have shrunk.