By this point, anyone who’s been covering or following COVID-19 knows that several comorbidities substantially increase the risk of complications and severe disease. Among those mentioned most often are diabetes, heart disease and obesity.
We learned of the associations between those conditions and more severe disease first from clinical anecdotes, then case series, then observational studies. But observational studies can almost never show causation. (I don’t think they can ever, on their own, show causation, but I add the “almost” because nothing in science is ever absolute.) Although diabetes is linked to poorer outcomes with COVID-19, it doesn’t mean having diabetes causes poorer outcomes. Continue reading