People Lacking a Sense of Smell Breathe Differently, Study Finds

The study identified how loss of smell changes breathing.

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People born without a sense of smell breathe differently than those with a normal sense of smell, according to a new study published Tuesday.

This discovery may help explain the broader health impacts associated with anosmia—the inability to perceive odors—which has been linked to depression and increased mortality rates.

Key Findings

Researchers found that compared to people with an intact sense of smell, those with anosmia had two significant differences in breathing patterns.

“People with an intact sense of smell have these small micro-inhalations, what we refer to as ’micro-sniffs’” that blend into their regular breathing patterns, lead study author Noam Sobel, head of the Department of Neurobiology at the Weizmann Institute of Science, told The Epoch Times. These micro-sniffs appear to be part of how people constantly explore their environment to detect odors.

“The second difference was that just the overall pattern of their respiratory trace was different,” he added, meaning that those born without a sense of smell had fundamentally different breathing patterns than those with normal olfactory function.

People with anosmia have distinctive breathing patterns.

When awake, anosmic individuals take more pauses while inhaling and fewer deep breaths and have weaker exhalations, possibly affecting oxygen exchange and energy levels.

During sleep, their breathing is more unstable. This irregular breathing may affect sleep quality and cognitive and emotional regulation. Regular breathing patterns are closely linked to brain activity and well-being.

The study, published in Nature Communications, used a wearable device to measure airflow through the nostrils for 24 hours. Researchers compared respiratory patterns between individuals with congenital anosmia and those with normal smell function (normosmics).

Relationship Between Breathing and Smelling

The nasal cavity serves as both an airway for breathing and the primary sensory pathway for smell. These functions are intricately connected; our response to odors can directly influence our breathing patterns, with research showing that both the pleasantness and intensity of smells can affect the depth and rate of inhalation.

A 2009 study found that exposing people to certain smells during sleep altered their breathing patterns and caused subtle changes in their breathing, reducing inhalation and increasing exhalation regardless of sleep stage or whether the scent was pleasant or unpleasant.

Reinforcing this connection, another study found that exposing people to a bad smell during a task reduced the amount of air people inhaled.

Breathing Reveals One’s Sense of Smell

Whether a person has an intact sense of smell may be identified through their breathing patterns, the researchers found.

While the overall breathing rate remained consistent between both groups in the new study, people with anosmia showed significantly fewer micro-sniffs, particularly during waking hours, suggesting normosmics sniff more to explore their environment.

While normosmic people sniff their environments more than anosmic people, inside an odor-free environment, the sniff rate of normosomic people decreases to match that of anosmic people. Normosomic people may even sniff less than anosmic people.

This shows that the additional micro-sniffs among normosmics arise from these people’s interactions with scents in the environment.

The researchers didn’t stop at analyzing micro-sniffs. Using a newly developed analytical tool, researchers identified four distinct breathing parameters that differed between groups. These differences were so pronounced that researchers could identify people with congenital anosmia with 83 percent accuracy based solely on their respiratory patterns.

Since the study focused exclusively on congenital anosmia, plans are underway to investigate whether similar breathing patterns exist in acquired anosmia.

Understanding Anosmia

Approximately 3 percent of Americans experience anosmia or hyposmia (reduced ability to smell). Anosmia can be acquired or congenital and temporary or permanent. Some of the common causes of anosmia include direct obstructions such as sinusitis or tumors, nerve and brain tissue damage from trauma, toxic agents, infections like COVID-19, and neurodegenerative diseases such as Alzheimer’s.

Impact on Quality of Life

Although often dismissed as a sense with a minor role in daily life, olfaction is far more critical. Losing the ability to smell affects more than just detecting scents.

“I have congenital anosmia,” David, a 41-year-old software engineer from San Jose, California, told The Epoch Times. “It’s genetic. My mom doesn’t have a sense of smell, nor did her dad. I had an MRI a few years ago and learned I don’t have olfactory bulbs, which is the reason I can’t smell.”

Not having a sense of smell causes some difficulties, David said. “Not being able to smell if there’s a gas leak is a concern at times. I can’t smell if food has gone bad, so I rely on ‘use by/sell by’ dates and end up tossing leftovers if they’re questionable,” he noted.

His sense of taste has been affected as well. “Mint, basil, spinach, and cilantro all taste the same; it’s the ‘green, leafy taste,’” he said.

Anosmia’s impact on taste may be tied to the close connection between smell and taste. In addition to smelling through the nose, we can also smell “backward,” wherein odors from the back of the throat travel to the nose, allowing us to perceive smells in reverse, further affecting taste perception.

Some who have lost their sense of smell report poorer quality of life, including feelings of isolation, insecurity, and inability to feel pleasure. It can also negatively affect social interactions, communication, and confidence in work and other social environments, resulting in discomfort in social gatherings and workplace settings.

While it has its downsides, being unable to smell things may have some benefits, too. “Our dog got skunked one time and I couldn’t smell it while I cleaned it off him. I did need someone else to check that I got it all, however,” David said.

Promising Role of Olfaction in Health and Well-Being

Aside from the impact of anosmia on breathing patterns, olfaction’s role in brain function and overall health and well-being in general is a promising area of study. Case in point, the link between respiratory patterns and brain activity is a hot topic in the human neuroscience field, according to Sobel.

“There’s lots and lots of work on this, where it’s clear that patterns of breathing, particularly nasal airflow, more than other types, influence these patterns of brain activity and are linked to cognitive and emotional processing,” he said. For instance, a study showed how breathing subtly modulates brain activity for functions like sensation, cognition, and emotions.

“We’ve been applying this device in several diseases now … and we’re seeing altered patterns of long-term respiration in several conditions,” Sobel said.

The researchers believe people’s breathing patterns may be used to help diagnose diseases in the future.

For instance, olfactory impairment is seen as an early functional marker for neurodegenerative diseases like Alzheimer’s disease because of how problems in identifying and recognizing smells precede cognitive changes in those with the disease. Additionally, it has been proposed as a novel marker for autism spectrum disorder (ASD).

“In many of these conditions, it’s indeed going to be our goal to try and develop respiratory patterns to reverse the effects [deleterious outcomes associated with conditions],” Sobel said. However, he emphasized that they are far from this stage.