Tuesday, May 12, 2020

No, Smoking Won't Keep You from Dying of COVID-19

You may have seen news of a scientific paper that seems to indicate that smoking reduces the risk of dying from COVID-19. However, that isn't the case, because the numbers used in the study don't actually imply that. This analysis shows the difficultly in evaluating statistics in systems with complex and related variables. It's written by an actual epidemiologist so I would trust this more than what you will see in the popular press (or on social media).
There’s a new paper circulating today about “risk factors” for COVID19 which is getting misinterpreted in a pretty common way: applying conclusions about causation to results obtained via methods designed only for finding correlations.

It’s time for a #tweetorial!
 Here is the study that inspired this tweetorial. 

They looked at a truly huge number of people presenting to medical care in the UK and then compared how common it was for people to die in hospital from COVID across a whoooooole bunch of different types of people.
Based on those comparisons, they highlight some characteristics which correlated with COVID death as potential having risks or benefits. 

Some agree with what we already know: eg older age, certain comorbidities. 

Others are counterintuitive: especially “current smoker” status
Why is that counterintuitive? Current smokers should be expected to, on average, have less healthy lungs than never smokers (and maybe even former smokers), and we know COVID19 can kill people by attacking their lungs.
This is where the “disease detective” skill set of an epidemiologist comes in. 

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