Cochrane review on mask wearing

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Woodchopper
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Cochrane review on mask wearing

Post by Woodchopper » Thu Feb 23, 2023 1:44 pm

New review published on 30 January.

In order to increase the number of studies it covers influenza as well as Covid. Concludes that there there is little high quality research and overall masks don’t appear to help, but hand washing does.
We obtained the following results:

Medical or surgical masks

Ten studies took place in the community, and two studies in healthcare workers. Compared with wearing no mask in the community studies only, wearing a mask may make little to no difference in how many people caught a flu-like illness/COVID-like illness (9 studies; 276,917 people); and probably makes little or no difference in how many people have flu/COVID confirmed by a laboratory test (6 studies; 13,919 people). Unwanted effects were rarely reported; discomfort was mentioned.

N95/P2 respirators

Four studies were in healthcare workers, and one small study was in the community. Compared with wearing medical or surgical masks, wearing N95/P2 respirators probably makes little to no difference in how many people have confirmed flu (5 studies; 8407 people); and may make little to no difference in how many people catch a flu-like illness (5 studies; 8407 people), or respiratory illness (3 studies; 7799 people). Unwanted effects were not well-reported; discomfort was mentioned.

Hand hygiene

Following a hand hygiene programme may reduce the number of people who catch a respiratory or flu-like illness, or have confirmed flu, compared with people not following such a programme (19 studies; 71,210 people), although this effect was not confirmed as statistically significant reduction when ILI and laboratory-confirmed ILI were analysed separately. Few studies measured unwanted effects; skin irritation in people using hand sanitiser was mentioned.
On the quality of data:
Our confidence in these results is generally low to moderate for the subjective outcomes related to respiratory illness, but moderate for the more precisely defined laboratory-confirmed respiratory virus infection, related to masks and N95/P2 respirators. The results might change when further evidence becomes available. Relatively low numbers of people followed the guidance about wearing masks or about hand hygiene, which may have affected the results of the studies.
Link to the review:
https://www.cochrane.org/CD006207/ARI_d ... ry-viruses

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bob sterman
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Re: Cochrane review on mask wearing

Post by bob sterman » Thu Feb 23, 2023 8:22 pm

Given this...
Relatively low numbers of people followed the guidance about wearing masks or about hand hygiene, which may have affected the results of the studies.
...it might better be described as a review of the effectiveness of mask wearing guidance rather than mask wearing itself.

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Re: Cochrane review on mask wearing

Post by shpalman » Thu Feb 23, 2023 9:22 pm

In more than 300 pages of pdf it seems like the papers on mask wearing in the population during the covid pandemic are two of them, one of them being
shpalman wrote:
Fri Nov 19, 2021 10:01 am
Well it has a slightly different title compared to that earlier preprint but I assume the same authors didn't do two of them.

Normalizing Community Mask-Wearing: A Cluster Randomized Trial in Bangladesh Abaluck et al. (what's the "Yale School of Management"?)

(link to the BMJ editorial: "the research on this is sh.t, here's an example" for convenience)
and the other being the ref (66) Bundgaard mentioned here:
shpalman wrote:
Fri Nov 19, 2021 9:45 am
Image

(66) Bundgaard: https://doi.org/10.7326/M20-6817 (this is the "one randomized controlled trial")
(63) Doung-ngern: https://doi.org/10.3201/eid2611.203003
(43) Krishnamachari: https://doi.org/10.1016/j.ajic.2021.02.002
(36) Lio: https://doi.org/10.1186/s12889-021-10680-5
(60) Xu: https://doi.org/10.2196/21372
(57) Wang: https://dx.doi.org/10.1136/bmjgh-2020-002794
Mask wearing and covid-19 incidence—Six studies with a total of 2627 people with covid-19 and 389 228 participants were included in the analysis examining the effect of mask wearing on incidence of covid-19 (table 1) [36,43,57,60,63,66]. Overall pooled analysis showed a 53% reduction in covid-19 incidence (0.47, 0.29 to 0.75), although heterogeneity between studies was substantial (I2=84%) (fig 5). Risk of bias across the six studies ranged from moderate [36,57,60,66] to serious or critical [43,63].
having that swing is a necessary but not sufficient condition for it meaning a thing
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Re: Cochrane review on mask wearing

Post by shpalman » Thu Feb 23, 2023 9:33 pm

Oh and thinking that influenza and covid behave in the same way brought you "four weeks behind Italy".
having that swing is a necessary but not sufficient condition for it meaning a thing
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Grumble
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Re: Cochrane review on mask wearing

Post by Grumble » Thu Feb 23, 2023 10:48 pm

where once I used to scintillate
now I sin till ten past three

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Re: Cochrane review on mask wearing

Post by IvanV » Fri Feb 24, 2023 11:30 am

Grumble wrote:
Thu Feb 23, 2023 10:48 pm
Steve Novella is not impressed
https://sciencebasedmedicine.org/masks-revisited/
Worth spelling out his headline.
A recent Cochrane review, limited in scope and problematic in methodology, does not show that masks do not work, despite common misreporting.
Cochrane reviews are unfortunately sometimes problematic. Edzard Ernst was convincingly scathing about Cochrane reviews which appeared to show that acupuncture was useful for pain control, as a letter in the current Private Eye reminded us.

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Re: Cochrane review on mask wearing

Post by Herainestold » Sun Feb 26, 2023 6:27 pm

Masks work. We know that.
Double masking helped India to beat the Delta variant.
Masking forever
Putin is a monster.
Russian socialism will rise again

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Woodchopper
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Re: Cochrane review on mask wearing

Post by Woodchopper » Sun Mar 12, 2023 1:49 pm

Karla Soares-Weiser, Editor-in-Chief of the Cochrane Library, has stated:
Many commentators have claimed that a recently-updated Cochrane Review shows that 'masks don't work', which is an inaccurate and misleading interpretation.

It would be accurate to say that the review examined whether interventions to promote mask wearing help to slow the spread of respiratory viruses, and that the results were inconclusive. Given the limitations in the primary evidence, the review is not able to address the question of whether mask-wearing itself reduces people's risk of contracting or spreading respiratory viruses.

The review authors are clear on the limitations in the abstract: 'The high risk of bias in the trials, variation in outcome measurement, and relatively low adherence with the interventions during the studies hampers drawing firm conclusions.' Adherence in this context refers to the number of people who actually wore the provided masks when encouraged to do so as part of the intervention. For example, in the most heavily-weighted trial of interventions to promote community mask wearing, 42.3% of people in the intervention arm wore masks compared to 13.3% of those in the control arm.

The original Plain Language Summary for this review stated that 'We are uncertain whether wearing masks or N95/P2 respirators helps to slow the spread of respiratory viruses based on the studies we assessed.' This wording was open to misinterpretation, for which we apologize. While scientific evidence is never immune to misinterpretation, we take responsibility for not making the wording clearer from the outset. We are engaging with the review authors with the aim of updating the Plain Language Summary and abstract to make clear that the review looked at whether interventions to promote mask wearing help to slow the spread of respiratory viruses.

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Woodchopper
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Re: Cochrane review on mask wearing

Post by Woodchopper » Sun Mar 12, 2023 2:12 pm

IvanV wrote:
Fri Feb 24, 2023 11:30 am
Grumble wrote:
Thu Feb 23, 2023 10:48 pm
Steve Novella is not impressed
https://sciencebasedmedicine.org/masks-revisited/
Worth spelling out his headline.
A recent Cochrane review, limited in scope and problematic in methodology, does not show that masks do not work, despite common misreporting.
Cochrane reviews are unfortunately sometimes problematic. Edzard Ernst was convincingly scathing about Cochrane reviews which appeared to show that acupuncture was useful for pain control, as a letter in the current Private Eye reminded us.
It seems to me that the Cochrane review is doing what Cochrane reviews do. I spent years pointing out to homeopaths and similar that there is a hierarchy of evidence and the lower down the hierarchy the more likely it is a that a finding in an article is incorrect. It doesn't appear that there are many randomized control trials, and the results from those are inconclusive.

We shouldn't be surprised because the most important questions are about whether encouraging people to wear masks or making it mandatory will affect community transmission of respiratory diseases. This isn't going to be an easy thing to study and comes with all the complexities of different amounts of compliance, not just whether or people follow the advice or rules, but how consistently and where, and are those who do what they are told more likely to be careful in other ways. Add to that the methodological difficulties in measuring community transmission and ethical issues around the control group.

This isn't to say that advice or rules around mask wearing were wrong. In the middle of a pandemic its reasonable to to ask people to do something that will probably help and has few side effects for the great majority of people. I wore masks when the public health authorities recommended it, but I stopped when they stated that it was no longer needed.

It would be good if we could get better evidence. There will likely be another pandemic in our lifetimes and it would be good to have a much better idea not just of the overall effectiveness but the optimal timing of interventions. I hope that the billions spent on medical research can include some funding for more studies on mask wearing.

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