Rapid loss of odor predicts brain changes in dementia

Studies show that as the sense of smell declines over time, cognitive loss is predicted, and structural changes in areas of the brain that are important in Alzheimer’s disease and dementia are predicted.

Results of a survey based on a longitudinal study of 515 elderly people published in Alzheimer’s Disease and Dementia: Journal of the Alzheimer’s Disease AssociationMay lead to the development of sensory test screening for early detection of cognitive impairment in patients.

“This study provides another clue to the rapid decline of sensation. odor It’s a great indicator of what happens structurally in a particular area of ​​the brain, “said a senior professor of surgery at the University of Chicago and an otolaryngologist who studies olfactory and sinus disorders. Author Jayant M. Focus states.

Alzheimer’s disease and dementia

It is estimated that more than 6 million Americans have Alzheimer’s disease. Alzheimer’s disease is characterized by other symptoms such as memory loss, mood swings and difficulty performing daily tasks. There is no cure for Alzheimer’s disease, but some medications can temporarily delay the condition.

Memory plays an important role in our ability to recognize odors, and researchers say that it is the sense of smell. dementia.. Plaques and tangles that characterize tissues affected by Alzheimer’s disease often appear in areas related to the sense of smell and memory before they develop in other parts of the brain. It is still unclear whether this damage actually causes a decrease in the human sense of smell.

Focus and his team wanted to see if they could identify changes in the brain that correlate with loss of human sense of smell and cognitive function over time.

“Our idea is that people who lose their sense of smell rapidly over time either slowly decline or feel worse than those who maintain a normal sense of smell, and have brain problems and even Alzheimer’s disease themselves. It was more likely, “Rachel says. She is a medical student at the University of Chicago Pritzker Medical College and the lead author of the study, Pasina.

The team used patient data anonymized from the Memory and Aging Project (MAP) of Rush University, a research group started in 1997 to study chronic aging and neurodegenerative diseases such as Alzheimer’s disease. did. MAP participants are seniors living in retirement or senior housing communities in northern Illinois and are tested annually for health parameters such as their ability to identify specific odors, cognitive function, and signs of dementia. Some participants also had an MRI scan.

Scientists say that a rapid decline in a person’s sense of smell during normal cognitive periods, a decrease in the amount of gray material in areas of the brain associated with odor and memory, cognitive deterioration, and dementia in these elderly people. In fact, the risk of loss of smell was similar to having the APOE-e4 gene, a known genetic risk factor for developing Alzheimer’s disease.

This change was most pronounced in the primary sensory region, including the entorhinal cortex, which is the main input to the amygdala and hippocampus, an important site of Alzheimer’s disease.

“The amount and shape of gray matter in the olfactory and memory-related areas of the brain of people with rapidly declining sense of smell could be shown to be smaller than in people with less severe sensation of smell.” Says Pinto.

Next step

Autopsy is the gold standard for determining if someone has Alzheimer’s disease, and Focus hopes to ultimately extend these findings by examining brain tissue for markers of Alzheimer’s disease. is. The team also studied the effectiveness of using the sense of smell in the clinic as a means of screening and tracking older people for signs of early dementia, similar to how they use visual and hearing tests. I want to develop a cure.

The Smell Test is an inexpensive and easy-to-use tool consisting of a series of sticks that look similar to a felt-tip pen. Each stick is infused with a distinct scent that an individual must identify from a set of four choices.

“Early identification of people in their 40s, 50s, and 60s at high risk may provide enough information to enroll in clinical trials and develop better medicines,” said Pacyna. increase.

The study was limited in that participants received only one MRI scan. That is, the team lacked data to identify when structural changes in the brain began or how quickly brain regions shrank.

“We need to study in relation to all the risk factors we know about Alzheimer’s disease, such as the effects of diet and exercise,” says Pinto. “Smell and odor changes must be one important factor in the context of a range of factors that we believe affect the brain in health and aging.

Also, most MAP participants were Caucasian, so additional research is needed to determine if the undervalued population is similarly affected. The team’s previous work showed significant racial disparities, and African Americans faced the most serious impairments of their sense of smell.

A previous study of focus examined the sense of smell as an important marker for reducing the health of the elderly. His 2014 paper found that older people who have no sense of smell are three times more likely to die within five years. It is a better predictor of death than a diagnosis of lung disease, heart failure, or cancer.

Additional researchers contributed from the University of Chicago and the University of Southern California.

Source: University of Chicago