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Comment by tgb | Hacker News Reader

So the mask group was also competely confounded with being infectious disease specialists? Perhaps there were other precautions besides masks and hand washing that they were taking due to their training, even if not explicitly. Still interesting, particularly given the widespread appearance of "don't bother with masks" articles these days.

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"Don't bother with masks" is actually "There is insufficient evidence to show that wearing masks is effective at preventing spread of disease", coupled with "Please don't take away our supply of masks that are for health care workers".

If masks didn't stop the spread of disease, nobody, even doctors, would bother. The problem is that mask usage writ large does not have a cost/benefit point that warrants recommendation by CDC.

I don't think you can call multiple elements to a protocol a "confounding factor".

Study: "wearing a mask and washing your hands has been shown to stop infection."

Critic: "This study is worthless, it can show which of these procedures was effective!"

Study: "uh, err..."

Confounding factors would uncontrollable factors that people couldn't implement themselves. People can clearly wash their hands and wear masks.

That's simply not what I said. The confounding factor isn't hand washing (though that also makes it impossible "model the effectiveness of respiratory masks" as the title says), it's that it's comparing one department to other departments, and those departments surely differ by more than just hand washing and face masks. Infectious disease specialists were trained differently, do different procedures, etc. They see patients with different symptoms and at different stages of their disease.

Essentially the way to treat this is not a study of N doctors but a study of only n departments, which turns it more into an anecdote - albeit a compelling one.

Most of the “don’t bother with masks” is usually about cheaper masks which are not rated N95.

Yes - that is what I noticed as well. The two populations have different levels of expertise re: dealing with airborne infectious diseases; different frequencies of hand-washing; and no masks vs. masks. There are just too many confounding factors here to draw a conclusion (in isolation) re: mask effectiveness.

Edit: in addition, the departments used to dealing with airborne infectious disease may have had specialized protocols and policies that the other departments did not have.

I do think that on a personal level, it was probably just more hand washing, the masks to prevent droplets and so on (that is, both groups could have done so, but the infectious disease experts are more likely to do so with every interaction).

However, one part of your comment stood out to me: the infectious disease units also have higher HVAC standards than say regular areas (e.g., https://www.hfmmagazine.com/articles/3246-studying-airflow-i...).

No.

Piling up multiple layers of a completely ineffective barrer does not make it effective.'

It'd be like trying to use layers of netting to hold back the sea.

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