key: cord-0689771-gfedxkow
authors: Hemilä, Harri
title: Benefit of OTC Formula Against COVID-19 Is Explained by Selection Bias
date: 2021-11-11
journal: J Evid Based Integr Med
DOI: 10.1177/2515690x211058417
sha: a966c85a9a6e44cfedd9cad5e3de7b59402b8260
doc_id: 689771
cord_uid: gfedxkow

nan

In the follow-up of the questionnaire-cohort of the Physicians' Health Study, age-adjusted overall mortality was 19% lower among 59 277 men who were willing to participate, compared with 52 883 men who were not willing to participate in the trial. 2 However, when baseline characteristics were taken into account, the adjusted difference fell to just 5% and was no longer a significant difference. Thus, essentially all of the significant 19% difference was explained by life-style and other differences between the two groups. For example, "those who were willing, tended to be younger, exercise more, and be less likely to have a positive disease history for several major chronic conditions". 2 Thus, the uniform set of criteria for sending the questionnaire to the large group of male physicians aged 40 to 84 years did not generate to a homogeneous group of men, and within the large group there were substantial systematic differences between those who were willing and those who were not willing to participate in the trial. In epidemiology this phenomenon is called selection bias. The purpose of randomization in randomized controlled trials (RCT) is to form two (or more) groups that do not have any systematic differences between the groups. Thereby the differences between the groups that appear during intervention can be attributed to the particular intervention.

There is RCT evidence that vitamin C may influence COVID-19, 3, 4 and that nasal carrageenan influences coronavirus infections. 5 Therefore, randomized trials on OTC treatments for the new coronavirus and other respiratory viruses should be encouraged. However, comparison of participants who are willing versus not willing to participate in a trial is fundamentally biased and therefore the findings of the Margolin study are not a valid measure of the OTC regimen effect. 1

The author declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

The author received no financial support for the research, authorship and/or publication of this article.

Harri Hemilä https://orcid.org/0000-0002-4710-307X

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Vitamin C May increase the recovery rate of outpatient cases of SARS-CoV-2 infection by 70%: reanalysis of the COVID A to Z randomized clinical trial

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