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People with higher body mass index (BMI) and older age are more likely to spread SARS-CoV-2 because they exhale more respiratory droplets, but a “nasal hygiene” product can reduce those, researchers say.
The study about age and BMI was published online February 9 in Proceedings of the National Academy of Sciences. It was conducted by David A. Edwards, Ph.D., founder and chief scientific officer of Sensory Cloud, Boston, Massachusetts, and formerly professor of bioengineering at Harvard University, Boston, and colleagues.
The results “raise the question, ‘What is causing some people to exhale many more respiratory droplets than other people?’ ” Edwards told Medscape Medical News. “This work shows that there are a few factors at least ― age, BMI, and particularly strong correlations with age times BMI and respiratory infection itself,” he noted.
Edwards’ company makes a product called FEND (“fast emergency nasal defence”) that is designed to suppress airway droplets in the nasal passages. It consists of a misting device and a calcium-enriched saline aerosol that is inhaled and lasts up to 6 hours.
He claims it may help to reduce the spread of COVID-19 and other respiratory infections, although other experts are not entirely convinced.
Does Age Multiplied by BMI Signify a Greater Risk of Spreading Virus?
In the new study, Edwards and colleagues measured exhaled respiratory particles in a total of 194 healthy persons at two different US sites and in eight nonhuman primates that had been experimentally infected with SARS-CoV-2.
Among the humans, those in the top 18% for the metric of BMI multiplied by age accounted for 80% of exhaled bioaerosols. In the animals, higher viral loads correlated with greater particle exhalation.
The study is the first to attribute COVID-19 “superspreader” capabilities to individual human characteristics, as opposed to events involving crowds or unmasked behaviors.
“We have done a number of other studies over the last 9 months, and we always see this. The signature of superspreading of airborne infectious disease may be quite directly related to this phenotypical variation in exhaled respiratory droplets between individuals,” Edwards said.
The finding of significant variation in the generation of respiratory droplets or in exhalation seems to reflect airway mucus barrier function, he explained.
“Part of your immune system is your mucus. So, when you lose that barrier function, there’s a weakening of the immune system. We think with all these factors ― [increasing] BMI, age, infection ― there’s a correlation between weakened immunity and more respiratory droplets.”
Asked to comment, Judith A. O’Donnell, MD, chief, Division of Infectious Diseases, Penn Presbyterian Medical Center, Philadelphia, Pennsylvania, told Medscape Medical News, “I think you have to take the data at face value ― as you get older and have a higher BMI, these are two potential risk factors for being someone who can spread respiratory aerosols more efficiently.”
However, O’Donnell adds that the findings might be stigmatizing to the populations in question, ie, older and heavier people. “It gives me a lot of pause. It does feel like it could be fairly easily misinterpreted.”
Masking “Still Important,” and BMI x Age Is a “Bit of a Dirty Metric”
O’Donnell notes that the article doesn’t mention the importance of masking for everyone, regardless of age or BMI.
“The mask is the equalizer here in terms of preventing spread. I think that’s a really important takeaway. Yes, this finding is interesting, and it can definitely give us some useful information, but masks are the way to mitigate this…. I would not treat people of a certain size or age differently.”
Also asked to comment, C. W. David Chang, MD, associate professor of facial plastic and reconstructive surgery, Department of Otolaryngology–Head and Neck Surgery, the University of Missouri, Columbia, Missouri, questioned the use of BMI multiplied by age as a study metric.
“Typically, if we were doing it scientifically in most papers, [we] would look at BMI and age on a multiregression analysis to see if they’re independent factors,” he said.
“They created a whole new metric ― BMI times age ― and it seemed to have some correlation when they looked at superspreader level…. It’s an interesting finding but a bit of a dirty metric…. BMI and age are probably proxies for something else,” Chang said.
“New Hygienic Practice?” Add to Masks, Hand Washing, and Distancing
The “nasal hygiene” product, FEND, is sold as a cosmetic cleanser, so the company wasn’t required to show efficacy in preventing transmission of any particular infectious disease, including COVID-19, in order to market it. The mist is sprayed in front of the face, not into the nose. The instructions call for two deep inhalations every 6 hours. The aim is to reduce the number of small exhaled particles that are below the size effectively filtered by masks.
The mister device costs $59.95, and the solution costs $10 per bottle. Each bottle contains enough solution for about 125 multiplied by “two inspiration uses.”
The combination of calcium and sodium salts strengthens airway mucus and exerts antimicrobial properties, Edwards said. “It’s helping your mucus do what it’s supposed to do. So, when pathogen comes in, it keeps it in your mucus so your body can clear it.”
Edwards began studying the use of inhaled salts over a decade ago, during the anthrax scare. After concern about anthrax faded, he was left without financial support for the work.
In July 2020, after the COVID-19 pandemic hit, his team wrote an article summarizing their previously unpublished animal data ― which involved their using various formulations of nebulized calcium chloride and sodium chloride against a variety of viral and bacterial pathogens ― as well as a small amount of human data.
“FEND is a first example of a new class [of] ‘airway hygiene’ [products] coming out in the context of the pandemic,” Edwards said. He noted that it fills a gap left by the “three pillars of hygiene,” masks, social distancing, and hand washing.
“Masks other than N95s don’t stop the smallest particles. Droplets less than a micron in size travel farther than 2 meters and can carry virus. Airway hygiene is removing those droplets from the air, so it’s a complement to masks and social distancing. It’s a new form of hygiene,” Edwards said.
But O’Donnell and Chang aren’t convinced.
“It’s not regulated. It makes me nervous,” O’Donnell said. She noted that it could potentially become contaminated if used improperly.
“There are a lot of unknowns there for me which would make me pause about making any recommendations on it. I’d really want to see a real scientific study that shows that it does anything and that it doesn’t harm…. I put it in the same category as unregulated dietary supplements,” she observed.
Chang said, “I find it difficult to believe. There’s nothing analogous in current medicine. We use saline irrigation into nasal passages to help with cleansing, but we don’t think of it as reducing respiratory droplets…. [A nasal hygiene mist] is not something we typically think of from an [ear, nose, and throat] perspective.”
Chang added that although it’s possible that FEND could reduce the spread of COVID-19, more data are needed to prove it. “They’ve developed an interesting product that shows some interesting capabilities, but then the next step is to really show that it makes a difference clinically,” he said.
Edwards is founder and CEO of Sensory Cloud. O’Donnell and Chang have disclosed no relevant financial relationships.
Proc Natl Acad Sci. Published online February 9, 2021. Full text
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