What went wrong in a highly publicized COVID mask analysis?


He COVID-19 pandemic is ongoing, but in May officials finalized his appointment as public health emergency. So it’s now fair to ask whether all our efforts to slow the spread of the disease – from wearing masks to washing hands to working from home – were worth it. A group of scientists has seriously muddied the waters with a report that gave the false impression that wearing masks didn’t help.

The group’s report was published by Cochrane, an organization that compiles databases and periodically publishes “systematic” reviews of scientific evidence relevant to health care. This year he published an article addressing the effectiveness of physical interventions to stop the spread of respiratory diseases such as COVID. The authors determined that the use of surgical masks “probably makes little or no difference” and that the value of n95 masks It is “very uncertain.”

The media reduced these statements to the assertion that the masks didn’t work. Under a headline proclaiming “Mask mandates did nothing,” New York Times Columnist Bret Stephens wrote that “the leading experts and commentators…were wrong” and demanded that they apologize for the unnecessary inconvenience they had caused. Other headlines and comments declared that “masks still don’t work,” that the evidence in favor of masks was “Approximately zero” that “Masks made ‘little or no difference’” and even that “12 research studies show masks didn’t work.”

Karla Soares-Weiser, editor-in-chief of the Cochrane Library, object to such characterizations of the review. The report had No He came to the conclusion that “masks don’t work,” he insisted. Rather, the review of studies on blinding concluded that the “results were inconclusive.”

In fairness to the Cochrane Library, the report made clear that its conclusions concerned the quality and ability of the available evidence, which the authors considered insufficient to demonstrate that blinding was effective. He was “not sure if the use of (surgical) masks or N95/P2 respirators helps slow the spread of respiratory viruses.” Still, the authors weren’t sure about that uncertainty either, saying their confidence in their conclusion was “low to moderate.” You can see why the average person might be confused.

This wasn’t just a lack of communication. The problems with Cochrane’s approach to these reviews run much deeper.

A closer look at how the mask report mixed things up is revealing. The study’s lead author, Tom Jefferson of Oxford University, promoted the misleading interpretation. When asked about the different types of masks, including N95s, he stated: “There is no difference, nothing like that.” In other interviewcalled mask mandates scientifically baseless.

Recently Jefferson has reclaimed that COVID policies were “evidence-free,” which highlights a second problem: the classic mistake of conflating absence of evidence with evidence of absence. The Cochrane finding was No that masking did not work but that scientists lacked sufficient evidence of sufficient quality to conclude that they worked. Jefferson erased that distinction, arguing in effect that because the authors couldn’t prove that the masks worked, they could be said to not work. That is wrong.

Cochrane has made this mistake before. In 2016, a flurry of media reports declared flossing a waste of time. “Do you feel guilty for not flossing?” he New York Times asked. No need to worry, news week It reassured us, because the “flossing myth” had been “destroyed.” But the American Academy of Periodontology, dental professors, dental school deans, and clinical dentists (including mine) said clinical practice reveals clear differences in tooth and gum health among flossers. and those who don’t. What’s going on?

The response demonstrates a third problem with the Cochrane approach: how it defines evidence. The organization states that its opinions “identify, evaluate, and synthesize all empirical evidence that meets prespecified eligibility criteria.” The problem is what those eligibility criteria are.

Cochrane reviews base their findings on randomized controlled trials (RCTs), often called the “gold standard” of scientific evidence. But many questions cannot be answered well with RCTs, and some cannot be answered at all. Nutrition is a good example. It is almost impossible to study nutrition with RCTs because you cannot control what people eat, and when you ask them what they have eaten, many people lie. Flossing is similar. One survey found that one in four Americans who said they flossed regularly were lying.

In fact, there is strong evidence that masks work to prevent the spread of respiratory diseases. It just doesn’t come from ECA. Comes from Kansas. In July 2020, the governor of Kansas issued an executive order requiring the use of masks in public places. However, just weeks earlier, the legislature had passed a bill authorizing counties to opt out of any state provision. In the following months, COVID rates decreased in the 24 counties with mask mandates and continued to increase in another 81 counties that chose not to.

Other study found that states with mask mandates experienced a significant decrease in the rate of COVID spread just days after the mandates were signed. The authors concluded that in the study period (March 31 to May 22, 2020) more than 200,000 cases were prevented, saving money, suffering and lives.

Cochrane ignored this epidemiological evidence because it did not meet his rigid standard. I have called this approach “methodological fetishism” when scientists fixate on a preferred methodology and discard studies that do not follow it. Unfortunately, it is not unique to Cochrane. By dogmatically insisting on a particular definition of rigor, scientists in the past have arrived at wrong answers more than once.

We often think of proof as a yes or no proposition, but in science, proof is a matter of discernment. Many studies are not as rigorous as we would like, because the messiness of the real world prevents this. But that doesn’t mean they don’t tell us anything. It does not mean, as Jefferson insisted, that masks “make no difference.”

The report on masks, like the previous report on dental floss, used “standard Cochrane methodological procedures.” It’s time for those standard procedures to change.

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