Anosmia, or loss of smell, has become a more popular term in recent years, thanks to the prevalence of this condition during the COVID pandemic. Researchers have studied anosmia for centuries, and have shown that it reduces quality of life and can be associated with it. depressionpremature mortality and other serious health outcomes. Now new research makes another distinction between those who can smell and those who can’t.
Humans with so-called congenital anosmia, who are born without a sense of smell, may breathe differently than people with the ability. These breathing differences may lead to different negative health outcomes associated with anosmia, researchers found in a study was published on Tuesday Nature Communications.
The idea that breathing and smell are connected is not entirely new. Zara Patel, an otolaryngologist at Stanford University who was not involved in the study, says humans are constantly probing the environment for smells. We take these signals and act on them to determine our behavior towards our environment and other people. Previous studies have also looked at the relationship between smell and breathing, but many of them have only been done in animals or in people who lost their sense of smell due to viral infections or other more common causes of anosmia. (According to the new show, congenital anosmia alone accounts for only about 4 percent of cases of the disease).
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“(This research) traces a mechanistic pathway that was previously unclear in humans,” says Valentina Parma, assistant director of the Monell Chemical Senses Center, who was not involved in the research.
The new study by Israeli researchers recruited 21 participants with isolated congenital anosmia and 31 people with normal sense of smell. Researchers developed a wearable device that measured nasal airflow.
“Being able to continuously monitor your breathing for 24 hours is a game-changer,” says Lior Gorodisky, a graduate student at the Weizmann Institute of Science in Rehovot, Israel, and first author of the study.. “After a few minutes, the participant is so used to that device that they behave as normal, which is very different from sitting in a lab, fully aware of the situation.”
The researchers then analyzed the 24-hour data to see how breathing differed between the two groups of people. While both groups breathed at the same general rate, breathing patterns were “profoundly altered” in the group with anosmia, the researchers wrote in the study. Those with a normal sense of smell had small respiratory peaks with each breath. These microsniffs did not occur when the participants spent time in an odorless room, suggesting that their goal was only to detect the odor.
“It’s what we think: it’s doing a kind of olfactory survey of the world,” says Noam Sobel, a neurobiologist at the Weizmann Institute of Science and one of the study’s authors. “You keep asking, ‘Is there a smell in here?'”
The study also found that there was a subtle but statistically significant difference in the participants’ overall breathing waveforms.
“This was significant, based on those differences alone, with 83 percent accuracy of who is anosmic and who isn’t,” says Sobel, “I don’t think there’s any other example of how you can tell who is or isn’t anosmic without using an odor for your test.” .
Despite the novelty of the research, it has some limitations. First, it has a small sample size. And it doesn’t track people throughout their lives, which is important because olfactory ability can change over time. The authors also acknowledge that for the control group they only asked people verbally about smell. Although all responded that their sense of smell was intact, it would have been more valuable to administer one. smell test.
Furthermore, the study is about people with congenital anosmia, that is, the population not so widely studied as do those with other types of smell loss. But anosmia is more often acquired through a viral infection like COVID, a traumatic brain injury, or neurodegenerative diseases like Parkinson’s or Alzheimer’s.
The researchers “used a population of patients who had never lost their sense of smell, so it would be nice to see if that holds up in patients who lost their sense of smell years ago,” says Eric Holbrook, director of the division of rhinology. Massachusetts Eye and Ear, which was not involved in the study.
Patel also points out that people with congenital anosmia tend to have a typical sense of taste, meaning they have developed some sort of compensatory mechanism where they can still taste and enjoy food. “Maybe they’re ‘sampling their environment’ through the oral cavity as opposed to the nasal cavity,” he says. This raises the question of whether the breathing patterns of people with congenital anosmia actually change. nasal only breathing patterns change, considering that only nasal breathing was measured in this study.’
The researchers also linked the results to negative health outcomes of anosmia, such as reduced quality of life and higher mortality rates, which Holbrook disputes. “They’re trying to link that to the reason why people associate increased mortality with increased cognitive dysfunction with loss of smell,” he says. “That would take a lot of work to prove.”
Parma has also stated that while there research showing that the rhythm of one’s breathing can activate the prefrontal cortex and help regulate emotions, more needs to be done before assuming it can cause emotional problems. “Additional validation needs to occur before we can assume causality between depressive symptoms or emotional dysregulation and this airway mechanism,” he says. “Further research needs to be done to prove all the steps.”
It’s something Sobel and his team are well aware of, and they hope to explore more in the future as they continue to experiment with the wearable device the lab has developed. “There appear to be significant cognitive effects of the respiratory phase, but the respiratory effects we found here are speculative,” says Sobel, “and indeed material for further research.”
However, says Paule Joseph, a chemosensory researcher at the National Institute on Alcohol Abuse and Alcoholism, the study demonstrates that anosmia is not just a loss of the ability to smell.
“This study advances the field by reframing anosmia as a condition with both sensory and physiological dimensions,” says Joseph, who was not involved in the study. “This research lays the groundwork for future interdisciplinary collaboration to fully understand and address the wide-ranging effects of anosmia, particularly in diseases such as Alzheimer’s, where the intersection of anosmia and respiratory function can exacerbate cognitive decline.”
