The Fögen Effect Masks a Big Methodological Issue


Have you heard of the Fögen effect, alternatively spelled “Foegen?” It is the idea, or so goes the claim, that wearing a mask could make COVID-19 more severe. And you might be tempted to take it seriously because it has a very scientific-sounding name. Surely, if this mechanism of action has been baptized in the scientific literature—with a German name to boot!—it must be genuine.

Fearmongering about mask wearing is nothing new, and this putative effect is simply the latest salvo in this campaign. It comes from a paper entitled “The Foegen effect: A mechanism by which facemasks contribute to the COVID-19 case fatality rate,” published earlier this year.

And it is deeply flawed.

Who makes the claim?

Before delving into the data and its analysis, I believe it’s important to submit this paper to that most important of all scientific analyses, the sniff test. Most people are not equipped to evaluate the calculations made in this paper, but everyone has a nose, and that nose can be trained to pick up on questionable smells.

Where does the name “Fögen effect” come from? Why, it comes from Dr. Zacharias Fögen, the sole author on this paper. On his website, Dr. Fögen describes himself as “a doctor from Kassel, Germany.” He has a page on ResearchGate, where researchers list their scientific publications, and his sole contribution is the present paper (accompanied by three preprints that are versions of this paper). A search on PubMed of his name only returns the current paper. Said paper declares that every aspect of this study, from its conceptualization to its writing, reviewing and editing, was done solely by Dr. Fögen. And he named the effect after himself.

It is highly unusual for a scientist in the present day to detect something new and decide to name it after themselves. Researchers might instead resort to funny names, like calling a gene Sonic hedgehog after the videogame character, or to a purely descriptive (and some might say boring) name. If they are lucky, the scientific community may retrospectively give the names of researchers to the phenomenon they discovered. But for a solo doctor to name what he has allegedly discovered after himself and to front-load this absence of humility in the title of his paper? It should raise a few olfactory flags.

On his website, Dr. Fögen refers to the public health measures against COVID-19 as “immoral” and “illegal,” and he has published a layman’s version of his paper on the website of the Brownstone Institute, an offshoot of the Great Barrington Declaration which frequently opposes COVID-19 mitigation measures.

For the record, this is not an ad hominem. There is a contingent of people online—sometimes referred to as “logic bros”—who misappropriate the language of critical thinking to defend unscientific views, and they often refer to the above as an ad hominem attack, meaning that I’m attacking the person making the argument and not the argument itself.

A classic ad hominem would go something like this. Let’s say that Charles Manson claims the Earth does not go around the Sun. Charles Manson committed murder, which is horrific, reeks of mental instability, and signals untrustworthiness. I reject the claim that the Earth does not go around the Sun because Charles Manson said it and he is a vile human being. I happen to be right in the process, but I am right for the wrong reason: I am dismissing what he says because of who he is instead of evaluating the claim itself.

But who a person is should not always be ignored. If Andrew Wakefield, disgraced physician turned anti-vaxxer, makes a vaccine documentary that you don’t have time to watch, you can dismiss the movie as wrongheaded and are likely to be right in that assessment.

Again, most people will not be able to make sense of the calculations Dr. Fögen presents, but they can see that this is a doctor who has seemingly never published research before, who has named his discovery after himself, who has opposed public health measures against COVID on his blog, and who has published a version of his paper on the website of an organization known for taking a stand against masking and vaccines.

This is not an ad hominem. This is learning that birds of a feather flock together. Not enough to dismiss the entire claim, but informative nonetheless.

However, let’s put all of that aside and look at the paper itself. Are face masks really killing people by causing more severe COVID-19 infections, as Dr. Fögen claims?

An ecological problem

What Dr. Fögen did was to use data from another study about people who live in the state of Kansas.

For the period of August 1st to October 15th, 2020, he looked at which counties in Kansas had a mask mandate and which did not. After making a number of corrections to this analysis (more on that later), he declared that counties with a mask mandate, in which one might expect fewer deaths from COVID-19, actually had more people diagnosed with COVID dying from it than counties without a mask mandate.

I put this paper to Dr. Christopher Labos, a cardiologist with a Master’s degree in epidemiology who is affiliated with our Office. What stood out to him was the fact that Fögen’s analysis falls prey to the ecological fallacy, a well-known problem in epidemiology.

Perhaps the most famous example of the ecological fallacy was the 2012 note published in The New England Journal of Medicine comparing country-wide chocolate consumption and the number of Nobel laureates that emerged from those countries. The graph, widely reported in the media, showed a straight line. The more chocolate was consumed in a country, the more Nobel prize laureates it had. The author, a physician in New York named Franz Messerli, hypothesized that flavanols seem to be effective in slowing down brain performance in aging, and chocolate has those in spades, so maybe those amazing scientists benefited from their brain-boosting effect. Messerli later admitted the whole thing, while based on real data, was a joke showing “the fallibility of science,” though the media certainly weren’t in on it.

The ecological fallacy is when information about a population is used to make assumptions about individuals within that population. It’s mistaking the forest for the trees.

The fact that the people of Switzerland, for example, consume a lot of chocolate does not tell us if Nobel laureates from Switzerland themselves consume more chocolate. We would need to question these scientists about their chocolate consumption to even begin to make a dent in that question.

That people in a particular Kansan county were mandated to wear a mask does not tell us if the people there who died of COVID did wear a mask, or how often they wore their mask, or if they wore their mask correctly or if they felt that protecting their chin was more important. To conclude that the masks caused the severity of their disease is not only to mistake a correlation for causation, but to commit the ecological fallacy by assuming that a county-wide rule necessarily informs us on an individual’s behaviour.

A similar paper by Beny Spira makes the same mistake, looking at mask compliance and deaths from COVID in Europe.

To be fair, it is hard to bypass ecological studies when wondering if wearing a mask is beneficial, neutral, or harmful to the spread and severity of COVID. But there are ways to minimize the problems ecological studies attract.

One of them is to look beyond a single state during a two-and-a-half-month period and consider multiple places at different points in time. Another one is to better control for variables. Deaths from COVID-19 are influenced by a lot more than whether or not people are wearing masks indoors. They are impacted by how much of the virus is circulating in the community, whether or not large gatherings have been banned, and the capacity the local hospitals have to take care of people requiring hospitalizations. These are not things Dr. Fögen took into account. Crucially, the deaths he attributes to COVID were not necessarily recorded as such; he infers they were due to COVID by removing certain types of deaths, like early infant mortality and suicides, from all of the deaths recorded in those counties.

Better ecological studies do not support Dr. Fögen’s claim that masking leads to more COVID deaths; in fact, these better studies lean in the opposite direction and also show that masking is associated with a slower speed of spread.

But Dr. Fögen thinks masking makes COVID worse and hypothesizes that what is causing this increase in COVID deaths is his so-called Fögen effect: that droplets containing the coronavirus land on the mask, the water content of the droplet dries out, leaving only the virus which is breathed in and which lands deep in the lungs because of its smaller size compared to the droplet. There, the virus causes pneumonia instead of a mere inflammation of the bronchi. Virus particles breathed out get breathed in again because of the mask, thus making the disease worse. And masks become sources of smaller aerosols by spreading these dried-out viral particles. At least, this is his hypothesis.

I asked Dr. Matthew Oughton, an attending physician at the Jewish General Hospital’s Division of Infectious Diseases, what he made of the idea that wearing a mask leads to more severe disease, and he referred to it as “an extraordinary claim.” Tuberculosis, like the coronavirus we are struggling with, is spread via aerosol droplets. “After working in the tuberculosis clinic for 14 years,” he wrote to me, “I am pretty sure that wearing respirators is beneficial and not deleterious to the health of those who wear them.” He was not aware of any evidence of mask use making a respiratory disease like COVID or tuberculosis worse. People infected with COVID can develop a range of illness severity, he told me, and doctors see pneumonia developing even in people who have never worn any kind of face covering.

There is another bit of evidence that Dr. Fögen brings up in his paper. He asserts that a famous experiment done at the beginning of the pandemic, which involved cages of hamsters in which the air circulating from one cage to the other was either unfiltered or had to go through a surgical mask, “proved the Fögen effect.”

He writes that whenever a mask was involved, the hamsters which developed symptoms of COVID-19 had more viruses in their lungs compared to the hamsters used in experiments where no mask was used. In actuality, while that is technically true for the hamsters sacrificed on day 5 of the experiment, it is not true for the hamsters sacrificed two days later. And even for the day 5 hamsters, we are dealing with 6 animals in the unmasked group versus 4 in the masked group, one of which had a viral load actually below the threshold of detection. This is hardly proof of anything.

A 1918 talking point

What the Fögen effect represents is the latest development in the “masks are making you sick” argument often deployed by people opposed to public health measures.

I remember the pamphlets that were distributed in some Montreal neighbourhoods at the height of the pandemic, scaring people into not wearing a mask. We were told they starved you of oxygen (not true), they filled you up with carbon dioxide (not true), and that they fostered bacterial growth, which would force you to breathe in disease-causing germs, a claim which goes back at least to the Anti-Mask League of San Francisco during the 1918 influenza pandemic. What always goes unsaid when these falsehoods are spread is that the surgeons and nurses and dentists and dental hygienists who have to wear masks daily do not regularly drop dead from having their noses and mouths obstructed.

The Fögen effect is ammunition for the people opposed to taking COVID-19 seriously. Case in point: it came to my attention because Joe Mercola, the snake oil king who is worth over $100 million, wrote about it for his newsletter.

The Fögen effect doesn’t even pass the sniff test, and that’s even when smelling it with a mask on.

Take-home message:
– The Fögen effect, named by and after Dr. Zacharias Fögen from Germany, is the assertion that wearing a mask can make a disease like COVID-19 worse by making the viral particle smaller as its water content dries up on the mask
– It is based on a deeply flawed analysis of data from the American state of Kansas and it goes against better evidence we have on mask wearing
– The Fögen effect is being used by people opposed to public health measures, like Joe Mercola, and is in keeping with their anti-mask rhetoric



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