Not having your sense of smell (or losing it) may be linked to changes in breathing that could lead to depression, social isolation or other mental and physical health problems, a new study suggests. It is further proof of how important this often neglected sense is.
A new analysis of respiratory data from 52 volunteers over a 24-hour period revealed that people with a normal sense of smell had small spikes, or “sniffs,” during each breath that were not seen in those with no sense of smell. according to the report published in the journal Nature Communications on Tuesday.
People can be born without a sense of smell, a condition called anosmia, or they can acquire it, as has been the case for many people who had a COVID infection.
Study volunteers without the ability to detect odors were born with that condition.
Nearly 1 in 4 people have anosmia, according to National Institutes of Health estimates. Experts say that figure is likely an undercount.
A 2023 report determined that more than 60% of people diagnosed with COVID developed anosmia. About 72% of them fully recovered their sense of smell, while about a quarter partially recovered it. Nearly 4% of people who were infected with COVID did not regain the ability to smell.
Even for those who belong to the 4%, there may still be hope, as some regain their sense of smell up to three years after infection, experts say. There are treatments that can help, such as smell training or a procedure known as a stellate ganglion block.
The main takeaway from the study is a better understanding of some of the mental problems experienced by some COVID patients who have lost their sense of smell, said the study’s lead author, Lior Gorodisky, a doctoral candidate in the department of brain sciences at the Weizmann Institute of Sciences in Rehovot, Israel.
The differences in breathing between those who can smell and those who cannot are quite significant. “We can now also identify lifelong anosmia based on breathing pattern alone,” Gorodisky explained in an email.
Small inhalations during a breath, known as the “sniff response,” are something most of us experience unconsciously every day, Gorodisky said. Those little sniffs tell our brain about good and bad smells. “When you go to a bakery or a flower field, once your brain smells the good smell of a cake or a flower, you immediately breathe deeper,” Gorodisky said.
To determine whether anosmia could affect breathing, the researchers gave the 52 volunteers nasal devices that monitored breathing as their days went by.
The authors noted that previous research has linked anosmia to a wide variety of negative outcomes, ranging from dulled emotions and depression to a shorter life expectancy.
Although people with anosmia in the study had had it their entire lives, the researchers believe their findings will apply to other people who developed the condition.
Loss of the ability to detect odors can lead to impaired memory for events linked to specific odors, Gorodisky said. Because of that, it can take the joy out of daily activities, like eating and socializing with friends and family.
As for the shorter life expectancy, that could be at least partly due to people not picking up odors that could signal danger, such as smoke, Gorodisky said.
A study published in August found that people who lost their sense of smell as a result of COVID-19 had behavioral, functional and structural changes in the brain.
The number of people with smell dysfunction is “vastly underestimated,” said Valentina Parma, associate director of the Monell Chemical Senses Center in Philadelphia.
The new study called it the “first step.”
“We’re gathering more reasons why we should pay more attention to the sense of smell,” said Parma, who was not involved in the new research.
The value of the sense of smell is often underestimated.
“For most of the world, smell is an afterthought,” Parma said. “COVID helped it become commonplace. It was a radical change.”
Currently, health care professionals don’t often ask or test for anosmia, Parma said. And that must change, since its development later in life has been linked to the onset of a number of serious disorders, such as Alzheimer’s and Parkinson’s, he added.
The findings underscore the importance of testing for anosmia and finding treatments, said otolaryngologist Dr. Jonathan Overdevest of Columbia University Irving Medical Center in New York City.
Researchers also need to determine the details of how the loss of the sense of smell can affect other aspects of health, Overdevest said. “One thing we do know is that a part of the brain initially affected by Alzheimer’s is responsible for the sense of smell,” he added.
Brain scanning studies have shown that the sense of smell connects with many aspects of thinking, said Benjamin tenOever, chair of the department of microbiology at New York University Langone Medical Center.
If there is a smell of noxious smoke, “neurons in the nose tell the brain that there is something dangerous to avoid,” tenOever said. “And when there is a pleasant smell, the brain tells the nose to increase the amount of air inhaled. It is not something that is done consciously, but rather the brain is programmed to do it.”
