key: cord-0888654-1gd9qvvn
authors: Jones, Alex L.; Satchell, Liam P.; Jaeger, Bastian; Schild, Christoph
title: (Mis-)understanding COVID-19 and digit ratio: Methodological and statistical issues in Manning and Fink (2020)
date: 2020-05-29
journal: Early Hum Dev
DOI: 10.1016/j.earlhumdev.2020.105095
sha: 29933ed30b8c770eb05edf22532308b033a6c649
doc_id: 888654
cord_uid: 1gd9qvvn

nan

In their study, Manning and Fink (1; henceforth M&F) ; report positive associations between the relative lengths of the index and ring fingers (2D:4D)-an intended proxy for prenatal exposure to testosterone-and two national COVID-19 outcomes: case fatality rate (CFR) and the percentage of male deaths (%MD). Whilst we encourage the production of science that can aid international responses to COVID-19, there are significant methodological and analytic concerns with M&F's paper that lead it to be uninformative in the current climate.

First, while M&F assume that 2D:4D functions as a proxy of prenatal testosterone, it should be noted that scholars have repeatedly pointed to the lack of evidence for this relationship (2-4) and 2D:4D findings across different contexts have failed to replicate (5).

Second, M&F set out to test the hypothesis that prenatal testosterone levels are associated with COVID-19 mortality risk. To test this, M&F examine data on national average 2D:4D and national COVID-19 outcomes. These variables in this study are sampled from separate populations and do not give insight into the proposed individual-level mechanism in M&F's discussion. Crucially, associations that hold at one level of analysis (e.g., nations), do not necessarily hold at another level of analysishere specifically at the individual level (6) .

Third, in their use of national aggregates for analysis, the number of cases for analysis are far from the claimed 103482 men and 83366 women. Rather, most of their analyses are Figure 1 

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