A new smell test has been conducted to identify people at higher risk of dementia, a collection of diseases that commonly affects older people. A nationally representative sample of participants was called back for a follow-up test after 5 years and those who hadn’t been able to identify at least 4 out of 5 odors were twice as likely to be diagnosed with dementia.

Since the olfactory nerve connects the cells that sense smell in the nose to the olfactory bulb located at the brain’s base, loss of odor detection can be an early indicator of the brain’s lack of ability to self-repair. The researchers developed a smell test as an attempt to confirm this theory for a study called Olfactory Dysfunction Predicts Subsequent Dementia in Older US Adults.

Participants were asked to identify odors like orange and leather. Image credit: Best Alzheimer's Products.
Participants were asked to identify odors like orange and leather. Image credit: Best Alzheimer’s Products.

Published in the Journal of the American Geriatrics Society, the research involved 2,906 men and women aged 57 to 85 who were interviewed and asked to complete a simple smell test. They had to identify fish, leather, orange, peppermint, and rose. As opposed to peppermint, leather was the hardest to identify from all five odors.

The participants had to detect them one at a time by sniffing a device like a felt-tip pen. They had to choose one correct option from a pool of four. About 80 percent of the people had the ability to correctly identify at least 4 out of 5 smells. Of those who couldn’t, 18.7 percent detected 2 or 3 of the scents, 2.2 percent identified just one, and 1 percent weren’t able to detect any of them.

The same team of researchers led by Jayant M. Pinto, a professor of surgery at the University of Chicago in Illinois, interviewed the participants again after 5 years to find out whether they had been diagnosed with any kind of dementia.

Loss of smell: an early sign of dementia

After analyzing the results of the smell test against the follow-up interviews, they found that the participants who had been able to identify less than 4 odors were more than twice as likely to be among those who had been diagnosed with dementia within the 5 years following the smell test. The chances of developing dementia were higher among the participants who had correctly detected a lower number of smells.

“We need to understand the underlying mechanisms so we can understand neurodegenerative disease and hopefully develop new treatments and preventative interventions,” said Pinto, as quoted by Mirror UK.

Rosa Sancho, research director at Alzheimer’s Research UK, considers that this study is an addition to the existing evidence that smell distortion could be an early warning that something is wrong in the brain. She said healthy people have the ability to distinguish as much as a trillion different scents, according to Mirror UK.

The condition is affecting more people each decade

The number of new dementia cases is increasing across the world. There are 47 million patients diagnosed with dementia worldwide and experts estimate the number will reach 75 million by 2030 and 132 million after two decades, according to a report by Medical News Today.

More than 93,000 people die each year from dementia-related causes in the U.S., according to the CDC. Image credit: Nursing Times
More than 93,000 people die each year from dementia-related causes in the U.S., according to the CDC. Image credit: Nursing Times

A progressive brain disorder, dementia disrupts cognitive function and patients lose their ability to remember, hold conversations, reason, and solve simple problems. The more advanced the collection of diseases is, the lower the chances to keep one’s personality and independence.

Although dementia cases are much more common in older people, it is not a normal part of aging. It appears when a person experiences impairment in two or more core mental functions. That leads patients to develop several diseases that affect their brain, which may include Alzheimer, frontotemporal disorders, Lewy body dementia, or vascular dementia. Sometimes people develop more than one type of these. Dementia has no cure and no treatments have been developed to diminish its effects on the brain.

However, recent conducted clinical trials might have a positive impact. Early diagnosis is key to find ways to improve the quality of life of patients and their loved ones can help if the collection of diseases is detected on time. Alzheimer’s disease, for instance, can start to produce brain damage ten years before a patient experiences symptoms.

The five-item smell test can help people at higher risk for dementia to prevent it in the early stages, as Dr. Stephen Thielke from the Psychiatry and Behavioral Sciences Faculty at the University of Washington in Seattle said in a linked editorial. The test could allow health workers to easily detect an early decline in brain functions and individuals who fail to identify at least 4 out of 5 odors can be put forward for trials of treatments.

Nevertheless, Dr. Thielke noted that smell testing alone is not enough to predict dementia. Similarly, Prof. Pinto admits that the test developed by his team simply detects people who should be closely monitored and that further research is needed so the test can become a useful tool in clinical practice.

Source: Mirror UK