Loss of Smell May Predict Alzheimer Disease and Dementia 

The loss of sense of smell is known to be associated with cognitive decline but has also been shown to predict brain atrophy associated with Alzheimer disease (AD) and dementia. New findings published in Alzheimer’s & Dementia suggests that smell-test screening could be developed to predict cognitive impairment.

“This study provides another clue to how a rapid decline in the sense of smell is a really good indicator of what's going to end up structurally occurring in specific regions of the brain,” said senior author Jayant M. Pinto, MD, a professor of surgery at the University of Chicago and ENT specialist who studies olfactory and sinus disease.
 
The decline of sense of smell was an indicator of multiple aspects of AD such gray matter atrophy in brain regions related to smell and memory, worse cognition, and higher risk of dementia in these participants. Brain atrophy was most noticeable in the primary olfactory regions, including the amygdala and entorhinal cortex.
 
“We were able to show that the volume and shape of grey matter in olfactory and memory-associated areas of the brains of people with rapid decline in their sense of smell were smaller compared to people who had less severe olfactory decline,” said Pinto.
 
Data for this study came from the Rush University’s Memory and Aging Project (MAP) in which participants (n=515) had their ability to identify certain smells, cognitive function, signs of dementia, and other health parameters tested annually. Participants were in their 70s and living in retirement or senior housing communities in Northern Illinois, but only some received MRI scans.

“If we could identify people in their 40s, 50s and 60s who are at higher risk early on, we could potentially have enough information to enroll them into clinical trials and develop better medications,” said Pacyna.

“We have to take our study in the context of all of the risk factors that we know about Alzheimer's, including the effects of diet and exercise,” said Pinto. “Sense of smell and change in the sense of smell should be one important component in the context of an array of factors that we believe affect the brain in health and ageing.
 
Differences in smell seen in prior studies have been correlated with racialized identities, making the low participation of Black, Hispanic, and Asian individuals an important limitation of this study.