A simple smell test could detect Alzheimer’s years before symptoms emerge

CHICAGO — Rapidly losing the sense of smell could help doctors detect Alzheimer’s disease years before symptoms emerge, a new study says. Scientists from the University of Chicago say losing the olfactory sense — a condition called anosmia — appears to be one of the first symptoms of the disease.

It predicts changes in brain regions important in dementia, opening the door to a cheap and non-invasive screening program. Such a test would be as routine as going to the doctor to check out your vision or hearing. Clinical trials on this connection are now in the planning phase.

“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,” says senior author and professor of surgery Jayant Pinto in a university release.

Early diagnosis of dementia is vital. So far, drug trials have failed because doctors end up prescribing these medications too late and only after the memory-robbing condition becomes visible. Memory plays a critical role in our ability to recognize odors. Scientists have long known of a link between sense of smell and dementia.

Scientists believe Alzheimer’s develops when plaques and tangles of rogue proteins gather around and disrupt neurons. The team analyzed data on 515 older people in Chicago, taking part in a memory and aging project since 1997. They demonstrated that it was possible to identify alterations in the brain that correlated with an individual’s loss of smell and cognitive function over time.

“Our idea was that people with a rapidly declining sense of smell over time would be in worse shape – and more likely to have brain problems and even Alzheimer’s itself – than people who were slowly declining or maintaining a normal sense of smell,” says Rachel Pacyna, a fourth-year medical student at the University of Chicago Pritzker School of Medicine.

Smell loss as big of a warning sign as Alzheimer’s genes

Researchers tested participants annually for cognitive function, signs of dementia, and their ability to identify certain smells. Some also received an MRI brain scan. A rapid decline in olfactory skills during a period of normal cognition predicted multiple features of Alzheimer’s disease. They included less grey matter in areas related to smell and memory, worse cognition, and higher risk of dementia onset.

In fact, the risk of smell loss was similar to carrying the APOE-e4 mutation — a known genetic risk factor for Alzheimer’s. The changes were most noticeable in primary olfactory regions called the amygdala and entorhinal cortex. They also have a link to the hippocampus – the brain’s memory control center which Alzheimer’s severely impacts.

“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,” Pinto says.

Finding Alzheimer’s in 40-year-olds?

An autopsy is the gold standard for confirming Alzheimer’s disease. Researchers hope to eventually extend the findings by examining patient brain tissue. The team is planning to conduct smell tests in clinics.

Older adults would be screened and tracked for early-onset dementia. The results could lead to the development of new treatments. Smell tests are generally inexpensive and easy-to-use. The tool, described in Alzheimer’s & Dementia, consists of a series of smelling sticks that are similar in appearance to felt-tip pens. Scientists infuse each of them with a distinct scent that individuals must identify from a set of four choices.

“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,” Pacyna adds.

Bigger studies taking more MRI brain scans may help pinpoint when structural changes in the brains begin or how quickly a patient’s brain shrinks.

“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,” Pinto continues. “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 aging.”

South West News Service writer Mark Waghorn contributed to this report.

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