Velvet Glove, Iron Fist: Smoking and COVID-19 - the evidence gets stronger
SATURDAY, 8 AUGUST 2020
I've found it impossible to keep up with all the research on smoking and COVID-19 recently. The tireless @phil_w888 has now catalogued over 700 studies of COVID-19 patients that have data on smoking prevalence.
In the last week, the largest observational study yet conducted found that smokers (in Mexico) were 23 per cent less likely to test positive for COVID-19. This is in line with the results of an ongoing meta-analysis by some researchers who would clearly prefer the hypothesis to be disproved but who nevertheless have found a 26 per cent reduction in infection risk for current smokers.
A study published in the Lancet a couple of weeks ago looked at the factors associated with COVID-19 caseloads at the national level. It found that countries with higher rates of smoking tended to have lower rates of Covid infection.
And a newly published prospective study of nearly 20,000 Covid cases tells a familiar story. Your chances of ending up in intensive care with the virus are increased if you are male, non-white, from a low income area, obese ... or a nonsmoker.
Note the telltale dose-response relationship. The heaviest smokers are an incredible 88 per cent less likely to end up in ICU with COVID-19.
The same rules apply to your chances of testing positive for COVID-19. Indeed, it seems increasingly clear that smokers are less likely to end up in intensive care with COVID-19 because they are less likely to catch it in the first place.
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The smoking finding, by contrast, continues to be ignored, although the evidence for a protective effect is about as a strong as the evidence for obesity being a risk factor.
And yet the association with smoking is not even mentioned in the abstract of the latest study (above), nor is it mentioned in the abstract of the Lancet study. The authors of the latter describe it as an 'unexpected finding' which 'requires further investigation'. The authors of the other study describe it as a 'counterintuitive finding' , although they do acknowledge that it is 'consistent with very low rates of smoking seen in patients presenting with COVID-19 in Wuhan and similar data from the USA and with the findings of a more limited analysis of patients with COVID-19 in France.
