Long COVID is a collection of health problems caused by COVID-19 that remain or appear following the initial infection. It is implausible that face masks cause long COVID, contrary to claims made online. Mask use can temporarily cause discomfort, but physiological effects are not biologically meaningful.
Update, May 19: The Frontiers in Public Health paper that served as the basis for claims that face masks could cause long COVID was retracted by the journal on May 12.
The retraction notice states: “Following publication, concerns were raised regarding the scientific validity of the article. An investigation was conducted in accordance with Frontiers’ policies. It was found that the complaints were valid and that the article does not meet the standards of editorial and scientific soundness for Frontiers in Public Health; therefore, the article has been retracted.”
Long COVID symptoms are varied, and researchers are still learning exactly how COVID-19 can lead to different symptoms that remain or appear after the initial illness. But there is no evidence, nor is it biologically plausible, that face mask use explains long COVID.
Citing a flawed paper published in Frontiers in Public Health, multiple social media posts baselessly suggest that people with long COVID symptoms may in fact be suffering from mask-induced exhaustion-syndrome, a bogus term previously coined by authors of the paper.
“Absolutely stunning: long Covid is really mask-induced exhaustion-syndrome (MIES),” tweeted Jeffrey A. Tucker, sharing a link to the study. Tucker is the founder and president of the Brownstone Institute, a group opposed to mandates and certain public health restrictions.
Many other posts shared an unsubstantiated article — “‘Long Covid’ Is Caused by Masks, New Study Finds” — from a website with a history of sharing inaccurate information on masks and vaccines. Posts about the new paper also bring up more general claims that masks can negatively affect the respiratory system and harm health.
But while there is evidence that COVID-19 can have a lasting impact on some people, there is no evidence that face masks, when used as recommended, have a negative impact on the respiratory system that could lead to any serious health problems.
The new Frontiers in Public Health paper endeavors to be a systematic review and meta-analysis, meaning that it rounds up studies on a topic that meet particular criteria and combines their data to draw larger conclusions. The study looked at past papers evaluating effects of mask use on physiological measurements and self-reported symptoms, without providing any data on masks and long COVID.
Instead, it contains statements speculating about a connection between long COVID and masks based on an overlap between various self-reported symptoms such as shortness of breath and headache.
“So far, several mask related symptoms may have been misinterpreted as long COVID-19 symptoms,” the researchers write. They do not provide any evidence that masks and long COVID are linked.
The paper also claims it shows that “masks interfered with O2-uptake and CO2-release and compromised respiratory compensation.” However, experts have pointed out multiple flaws and errors in the paper.
People do report feelings of discomfort, such shortness of breath, when they engage in physical activity while using face masks. But unlike long COVID symptoms, these feelings dissipate when they take off the masks. When researchers have measured physiological changes related to wearing masks, such as the concentration of oxygen or carbon dioxide in the blood, the effects have been minimal.
Dr. Susan Hopkins, a sports medicine physician and pulmonary and exercise physiology researcher at the University of California, San Diego, told us that the paper includes studies “that never should have been included because the data collection methods are flawed.” It also makes “a big deal of things that may be statistically significant but are biologically unimportant,” she said.
This is not the first time a Frontiers in Public Health paper has drawn criticism. The journal previously published and later retracted a paper presenting various debunked arguments that HIV does not cause AIDS. In 2016, it also preliminarily accepted a paper supporting the debunked idea that vaccines are linked to autism; the paper was rejected after significant concerns were raised.
Nor is it the first time the authors of the review have claimed face masks could have harmful effects. Several of the authors speculated in a review published in March that masks might have caused stillbirths and other health issues. But this was an extrapolation based on studies exposing animals to carbon dioxide — and ignored the fact that masks don’t increase levels of the gas in humans in any clinically meaningful way. The Daily Mail nevertheless covered the paper in a story with an alarming headline, screenshots of which have been widely shared on social media.
We reached out to a corresponding author for both papers — a surgeon in private practice in Germany — but did not get a response.
Study Relies on Faulty Data, Makes Serious Errors
The Frontiers in Public Health paper relies on data from past studies of masks. But Hopkins said the authors included studies with “faulty data.” For example, she said, they included a study with incorrect data on the volume of air subjects were breathing and the amount of oxygen they were consuming. She and her colleagues wrote a letter explaining that these data on breathing were biologically impossible based on other measurements taken at the same time in the same people.
The Frontiers paper claimed to find differences in the carbon dioxide concentration in the blood between people wearing and not wearing masks, but it based this conclusion on some studies that didn’t measure carbon dioxide in the blood. Instead, the the authors of these studies placed carbon dioxide sensors right outside of people’s mouths and tried to measure the amount of carbon dioxide they exhaled, Hopkins said.
That’s problematic, she explained, because it’s challenging to correctly place the sensor to “get an apples to apples comparison.” It’s also difficult to get a sensor that responds rapidly enough to detect the rises and falls in carbon dioxide as someone breathes in and out. Direct measurements of carbon dioxide in the arteries are trustworthy, she said. Well done studies have shown biologically insignificant impact from masks on carbon dioxide.
Other differences the paper purported to find between people with or without masks, such as oxygen saturation in the blood, are so small that they are “biologically unimportant,” Hopkins said, making an analogy to height: “If I told you I was 5-7, and you said ‘no, wait a minute, you’re not 5-7, you’re 5-6 and 15/16,’ I’d be like, ‘OK, sure, whatever.’”
Doctors and scientists also raised concerns online about the paper. On Twitter, Columbia University internal medicine physician Dr. Eric Burnett pointed out, among other issues, that one of the included studies says it used MRI to measure oxygen in the brain. “There is no way to do that using just an MRI so they made up a scoring system which isn’t tested or validated,” he wrote.
He and Gideon Meyerowitz-Katz, who is getting his doctorate at the University of Wollongong, also agreed that some differences in the paper between people wearing and not wearing masks are not “clinically significant” or “from a clinical perspective, not very meaningful.”
Meyerowitz-Katz also wrote in a Medium post that the Frontiers in Public Health paper itself “is absolutely filled with basic errors.” For example, he wrote, the authors incorrectly transcribed some numbers and sometimes just chose one group of people wearing masks to analyze when a paper had multiple masked groups.
Masks Do Not Cause Meaningful Physiological Changes
It’s no secret that many people find masks uncomfortable. “Masks make your face hot. They make your face sweaty. No question. Nobody disputes that. They make some people more aware of their breathing,” Hopkins said. But none of that means masks harm a person’s respiratory system.
There are a couple of theoretical ways a mask could impact the respiratory system, Hopkins said. Masks slightly increase something called dead space, equal to the volume of air that doesn’t make it out of a person’s airway when they breathe out. When a person breathes in again, the first air they take is a little more than a cup of old air from this dead space. Masks very slightly increase the amount of this old air people take in. To overcome this, a person just has to take a very slightly bigger breath.
As a person breathes, masks also increase resistance to air flow, which could at some point in theory make the lungs work harder to take in air.
However, the impacts from typical masks worn in everyday life, such as N95s, surgical masks or cloth masks, are very small. It is “not biologically plausible” that masks are “doing this big physiologic hit to your system,” Hopkins said.
Exercise physiologists know this in part because, starting before the pandemic, they have spent time trying to add resistance to breathing, in an attempt to better understand the human body and how the respiratory system can limit performance. This means that a person in a laboratory is hooked up to a device that can make it more difficult to suck in air and make the muscles work harder to breathe. Researchers then measure things like blood flow, heart rate, blood pressure, and oxygen and carbon dioxide concentrations in blood.
“We know that even when we try really hard to put huge loads on the respiratory system that it hardly does anything,” Hopkins said. “We’re talking two, three, four, five, six times the amount that a mask could possibly do.”
The available data on face masks worn outside of laboratory studies — like N95s or surgical masks — also does not show biologically important changes in measurements associated with breathing. A 2021 review published in Annals of the American Thoracic Society, co-authored by Hopkins, looked at studies of mask use during physical activity, concluding that “the effects on work of breathing, blood gases, and other physiological parameters imposed by face masks during physical activity are small, often too small to be detected, even during very heavy exercise.” Studies do suggest masks may temporarily increase a perception of shortness of breath, the researchers said.
A systematic review and meta-analysis by a different group of researchers, published in 2021 in Applied Physiology, Nutrition, and Metabolism, found that surgical or N95 masks did make people feel like they were exerting themselves more and were more short of breath, but this didn’t translate to a change in performance while exercising. They only slightly increased heart rate and carbon dioxide released at the end of a breath, although Hopkins again said that this type of carbon dioxide measurement is problematic. Regardless, the authors called the changes to these physiological measurements “minimal.”
Masks Are Not a Plausible Cause of Long COVID
There are logical flaws in the idea that masks — which can reduce the risk of someone catching the coronavirus in the first place — are behind long COVID.
As we’ve mentioned, the paper presents no evidence that people with long COVID are suffering from mask-related ills. There is a superficial overlap with some symptoms of long COVID and the subjective problems people report with masks, such as shortness of breath and headache. But long COVID has many additional manifestations and symptoms.
Causes of these symptoms are likely varied, according to a review study recently published in Nature Reviews Microbiology. For instance, problems like shortness of breath and cough are common lingering problems after infection that often eventually resolve. COVID-19 is, of course, a respiratory disease that can damage the lungs, and some studies of people with long COVID have shown lung abnormalities. Other problems, including a nervous system problem called dysautonomia, have been recorded in the aftermath of other infections before the pandemic.
As we’ve said, researchers are still looking into how COVID-19 leads to long COVID symptoms. Proposed mechanisms include virus remaining in tissues, impacts on the immune system, changes to the makeup of microbes in a person’s body, blood clotting issues, and effects on the nervous system.
Multiple experts online pointed out that long COVID is an ongoing health problem, while sources of discomfort associated with masks improve once a person takes off the mask.
Dr. Jonathan Laxton, a Canadian internal medicine physician, tweeted, “I have a clinic full of long covid patients – you think we’d notice they got better when they took their masks off?”
“[I]t’s a HUGE stretch to blame persistent long COVID symptoms on a mask that someone isn’t wearing,” Burnett tweeted.
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“Long COVID or Post-COVID Conditions.” CDC website. Updated 16 Dec 2022.
Kisielinski, Kai et al. “Physio-Metabolic and Clinical Consequences of Wearing Face Masks—Systematic Review with Meta-Analysis and Comprehensive Evaluation.” Frontiers in Public Health. 5 Apr 2023.
Kisielinski, Kai et al. “Is a Mask That Covers the Mouth and Nose Free from Undesirable Side Effects in Everyday Use and Free of Potential Hazards?” International Journal of Environmental Research and Public Health. 20 Apr 2021.
Tucker, Jeffrey A (@jeffreyatucker). “Absolutely stunning: long Covid is really mask-induced exhaustion-syndrome (MIES).” Twitter. 11 Apr 2023.
Burnett, Eric (@Doctor_Eric_B). “Not surprising that @jeffreyatucker from @brownstoneinst is pushing this absolute nonsense blaming long COVID on mask wearing. I read the study, so let’s chat about how ridiculous this claim is: a [thread]” Twitter. 13 Apr 2023.
Davis, Hannah E. et al. “Long COVID: Major Findings, Mechanisms and Recommendations.” Nature Reviews Microbiology. 13 Jan 2023.
“Use and Care of Masks.” CDC website. Updated 9 Sep 2022.
Hopkins, Susan R. et al. “Face Masks and the Cardiorespiratory Response to Physical Activity in Health and Disease.” Annals of the American Thoracic Society. Mar 2021.
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Male, Viki (@VikiLovesFACS). “The actual article does a reasonably good job of discussing some of the ways in which this scoping review may not apply to humans, but frustratingly this is not reflected in the headline at all! 1/.” Twitter. 24 Apr 2023.
Hopkins, Susan R. et al. “Effects of Surgical and FFP2/N95 Face Masks on Cardiopulmonary Exercise Capacity: The Numbers Don’t add up.” Clinical Research in Cardiology. 9 Oct 2020.
Burnett, Eric (@Doctor_Eric_B). “This is how I know folks haven’t actually read the studies. One of them used an MRI to measure brain oxygenation in mask wearers. Except one caveat: there is no way to do that using just an MRI so they made up a scoring system which isn’t tested or validated.” Twitter. 13 Apr 2023.
Gideon M.-K; Health Nerd. “Face Masks Are Safe To Wear.” Medium. 17 Apr 2023.
McDonald, Jessica. “What the Cochrane Review Says About Masks For COVID-19 – and What It Doesn’t.” FactCheck.org, 16 Mar 2023.
Laxton, Jonathan (@dr_jon_l). “Need any further proof @kevinnbass is not a medical expert? No, Kevin. Did you even read the study this nonsense was based on? The SpO2 and PCO2s were nornal. I have a clinic full of long covid patients – you think we’d notice they got better when they took their masks off?” Twitter. 12 Apr 2023.