Pick up the pace! Slow walkers four times more likely to die from COVID-19, study finds

[hlthe2b]

11. It is a confounded measure. BMI is an imperfect proxy for obesity (the extremely muscular

will be coded as obese), but it can be addressed with other variables. To use walking speed alone as a measure of fitness is far more problematic. So, no. The epidemiologic literature (not "Nature" would disagree). Walking distance and regularity may well be a far more accurate assessment, along with adjustment for other fitness activities (e.g., cycling) especially for a significant subpopulation. Alternately, nearly every elite athlete with walking-related disabilities or injuries would be assessed as unfit and thus assumed at risk for severe adverse outcomes from COVID-19. Not to mention the tons of other unaddressed confounding factors, from preexisting disease & conditions to concurrent medications to nutritional deficiencies impacting immunity to...

The study in the OP is ridiculously confounded--along the lines of the infamous comparison of Utah v Nevada populations that would have you conclude "gambling causes cancer." I know you are British, but look up the differences in Utah v Nevada populations if this is not obvious to you as the ultimate example of confounding.