People Born Without a Sense of Smell Have Different Breathing Patterns, Study Finds

Anosmia—the absence of the sense of smell—can feel like a significant loss during a stuffy, congested cold. Much of the time, however, we may take that sense for granted. For most people, sniffing is a natural, everyday act that flows with the cadence of inhales and exhales. But for those born without this sense, breathing takes on a different rhythm.

In a new study published in the journal Nature Communications on Tuesday, researchers found breathing differences among people with anosmia, which they suggest might account for the negative health issues associated with the condition. The altered patterns of respiration might impact health and emotion, according to the paper, though more research will be needed to prove it.

“There’s this notion that this sense is completely unimportant,” says Noam Sobel, a neuroscientist at the Weizmann Institute of Science in Israel, to the Guardian’s Nicola Davis. “And yet if you lose it, then a lot of bad things happen. So it seems like a paradox.”

To study anosmia and respiration, Sobel and his team examined 21 participants born with anosmia and 31 people who self-reported having a normal sense of smell. They measured respiration by using a wearable device that tracked the air flowing in and out of their nostrils over a period of 24 hours.

The researchers observed how breathing differed between the people who could smell and those who couldn’t. They found that those with a typical sense of smell conducted “exploratory sniffs” that created more inhalation peaks across the same number of breaths. The group with anosmia didn’t have these sniffs, which suggests they’re used for smell detection.

“What we think is: There is some sort of ongoing olfactory investigation of the world,” Sobel says to Scientific American’s Hannah Docter-Loeb. “You’re constantly asking, ‘Is there an odor here?’”

In fact, those with a normal sense of smell had about 240 more inhalation peaks per hour than the people with anosmia did. But when participants were in a room without strong smells, those exploratory sniffs largely did not occur, and the breathing patterns of both smelling and non-smelling people looked very similar.

The sense of smell “is the most primitive” one, Simone Gane, an ENT surgeon at the University College London Hospital who wasn’t involved in the study, tells Popular Science’s Lauren Leffer. “It’s hooked into a lot of the basic parts of our animal selves.”

The new study demonstrates that breathing, an essential function, goes hand-in-hand with the sense of smell, he adds, showing how important it is.

However, the study has some limitations. One of those is that it used only a small sample of people who were born without a sense of smell. And Zara Patel, an otolaryngologist at Stanford University who was not involved in the study, adds to Scientific American that these people have a typical sense of taste. So, they might still breathe normally through their mouths, for instance. “Perhaps they are ‘sampling their environment’ via the oral cavity as opposed to the nasal cavity,” she says.

According to the study, people born with anosmia represent only 4 percent of those with the condition. Most people without a sense of smell lose it through infection with a virus—for example, as a symptom of Covid-19—or through traumatic brain injury or neurodegenerative diseases, such as Alzheimer’s or Parkinson’s.

As a result, some scientists would like to see the same test performed on people who have acquired anosmia. Rachel Herz, a neuroscientist at Brown University, tells Popular Science that a lifelong inability to smell does not come with the same range of challenges that accompany a temporary loss of smell.

The researchers suggested the differences in breathing may be connected to reduced quality of life and higher mortality rates among people with anosmia, but “there is no literature suggesting that people with congenital anosmia are at higher risk” for these than those who acquire anosmia, Herz adds to Popular Science.

Notably, the study can’t definitively draw a link between breathing patterns and these negative health issues. “That would take a lot of work to prove,” says Eric Holbrook, a rhinologist at Massachusetts Eye and Ear who was not involved in the study, to Scientific American.

Until more research can be done, the paper offers a new look into a scientific field that is often under the radar. And it has opened up the possibility for more research, as Sobel and his team will now be able to experiment more with the wearable device they developed, reports Scientific American.

“It goes to show,” Gane tells Popular Science, “that we need to take olfaction a bit more seriously.”

Alexa Robles-Gil | | READ MORE

Alexa Robles-Gil is a bilingual science journalist based in New York City. Her work has appeared in the Guardian, Undark, Inside Climate News and more.