Cholesterol-lowering treatment may be a major cause of serious Covid-19 infections
Most researchers consider the association between low cholesterol and infection as reverse causality, meaning that it is the microorganisms or the inflammation which lower cholesterol. However, there is much evidence that the explanation is that low cholesterol predisposes to infection because, as I have mentioned in a previous comment (1), there is solid evidence that LDL partakes in the immune system by adhering to and inactivating almost all kinds of microorganisms and their toxic products (2). In accordance is a study of hospitalized patients with various types of infectious diseases, where those with the lowest LDL-C measured previously had the largest risk of developing sepsis and where the risk was highest among those on statin treatment (3).
As mentioned by Matteo Pirro (4) the authors of several studies have claimed that patients who have been prescribed statin treatment have a lower risk of infectious diseases. However, these studies have a serious bias, because the authors have not investigated whether the patients have continued the treatment. Therefore, the benefit may instead have been due to their high cholesterol because several studies have found that 40-80% of all statin-treated patients stop their treatment by themselves probably because statin treatment may cause many serious side effects (6,7). Thus, in the papers mentioned by Pirro the authors have compared people who may have had high cholesterol most of their life with untreated people, most of whom may have had normal or low cholesterol.
As mentioned by Pirro as well, no one has studied whether people with familial hypercholesterolemia (FH) are protected against infections. However, in a review of eight preliminary cholesterol-lowering trials using a PCSK9-inhibitor as treatment of hypercholesterolemic people, many of whom had FH, common adverse events were nasopharyngitis, upper respiratory tract infections and influenza (8).
That high cholesterol may be protective is evident because in a meta-analysis of 19 studies where the authors had followed more than 68,000 elderly people for several years, most of those with the highest LDL-cholesterol lived the longest. None of the studies found the opposite and after the publication of this analysis, at least eight studies including almost 700,000 individuals have come up with the same result (10-17).
There are therefore good reasons to stop statin treatment of patients with severe Covid-9 infection, also because at least 20 statin trials have been unable to lower mortality with statistical significance (7) and because more than 20% of statin-treated people suffer from serious side effects (6,7).
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Competing interests: No competing interests