Danish study finds face masks provide limited protection to wearer
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Re: Danish study finds face masks provide limited protection to wearer
#2Dane here, so I've read the study.
One of the important aspects here is of course the sample size, the timing of the study (during a downward trend in Denmark) and more importantly, it doesn't tell us if it protects others (which other research points to).
Re: Danish study finds face masks provide limited protection to wearer
#3"The findings are consistent with previous research. Health experts have long said a mask provides only limited protection for the person wearing it, but can dramatically reduce the risk to others if the wearer is infected, even when showing no symptoms. Preventing the spread to others is known as source control."
Re: Danish study finds face masks provide limited protection to wearer
#4>In the study, which was carried out in April and May when Danish authorities did not recommend wearing face masks, 6,024 adults were divided into two groups, one wearing face masks and one control group.
>After one month, 1.8% of the people wearing masks had been infected, while 2.1% of the people in the control group had tested positive, Copenhagen University Hospital said in a press release.
>The study does not confirm the expected halving of the risk of infection for people wearing face masks
>Participants reported their own test results; mask use was not independently verified, and users may not have worn them correctly.
So the control group had no masks, and the mask group were only told to wear a mask, and we have no data for how often they wore it. If their behavior is anything like what I'm seeing in the U.S., they're wearing it into the grocery store and going and seeing friends normally without a mask. The fact the study still produced a (likely statistically insignificant) 15% reduction in risk (1.8/2.1) is surprising under these circumstances.
Re: Danish study finds face masks provide limited protection to wearer
#5Here's the actual study.
https://www.acpjournals.org/doi/10.7326/M20-6817
The intervention being tested was merely how a RECOMMENDATION to wear a mask (and other advice and a pack of 50 surgical masks) may affect infection rates.
Of the mask wearers, and based on asking them and accepting their answers as truthful, 46% wore the mask as recommended, 47% "predominantly" as recommended, 7% not as recommended. The 7% were excluded from the results.
The infection in the area at the time was 2%. This gives relatively fewer chances for the efficacy of masks to be tested and so it is not surprising that the results are inconclusive. The benefit masks bring in this case is keeping the infection rate low and only actively do their job during the relatively rare times when an infected individual is near a healthy one.
The low infection rate also leads to an inflation of any systematic differences between the two samples. A very small difference applied to the expected 98% healthy subsample can lead to a strong contribution to the the 2% infected subsample. For example, mask wearing at the home was not covered and a few reported covid infections at the home.
Testing in places where infection rates are higher would have a better chance to show an effect. Of course that would be stymied by sample bias (if "random" self-selection of mask-wearers and anti-mask idiots were allowed in the procedures) or it would be faced with unethical practice of forcibly withholding masks from individuals in a non-mask sample.
My personal conclusion is that these results are not conclusive but will be hugely appropriated for whatever sick fantasy the outgoing US administration is orchestrating.
Re: Danish study finds face masks provide limited protection to wearer
#6I thought that it was accepted that the main benefit was in protecting other people. I wear a mask and a transparent face shield together. I believe that this combination offers me some protection and a lot of protection for people near me, so it seems like an obvious thing to do.
BTW, I find cloth masks not so comfortable, but the plastic face shield is no real additional discomfort at all.
Re: Danish study finds face masks provide limited protection to wearer
#7>In the study, which was carried out in April and May when Danish authorities did not recommend wearing face masks, 6,024 adults were divided into two groups, one wearing face masks and one control group. >After one month, 1.8% of the people wearing masks had been infected, while 2.1% of the people in the control group had tested positive, Copenhagen University Hospital said in a press release. >The study does not co…
> the mask group were only told to wear a mask
They were asked if and how they followed instructions and the 7% that said they did not were removed from the analysis. Only half of the remaining said they followed instructions. I also doubt the veracity of the replies. This is a weak point of the procedure.
Re: Danish study finds face masks provide limited protection to wearer
#8Mr Taleb comment on it: https://twitter.com/nntaleb/status/1329775819342934035
Re: Danish study finds face masks provide limited protection to wearer
#9I've been thinking: every one of us who's been on a plane is told how to wear an oxygen mask, every single time. I've never needed to do this, and in situations where its necessary then survival is already looking a bit dicey. There have been about 30,000 deaths from air crashes globally ever.
I wear a mask every time I go to the shops. I've never been given an official briefing on how to do it. There have been about 1,300,000 coronavirus deaths worldwide.
Re: Danish study finds face masks provide limited protection to wearer
#10I thought that it was accepted that the main benefit was in protecting other people. I wear a mask and a transparent face shield together. I believe that this combination offers me some protection and a lot of protection for people near me, so it seems like an obvious thing to do. BTW, I find cloth masks not so comfortable, but the plastic face shield is no real additional discomfort at all.
For me the discomfort is really about my glasses that get fogged.
It is much better with the FFP-3 masks than with the typical surgical ones.