Understanding Covid-19: Digit ratios and duration of oxygen therapy in hospitalized Covid-19 patients

Abstract

Background: Covid-19 severity shows a sex difference (males>females) and progressive hypoxia among the most seriously affected. Digit ratios are sexually dimorphic and may be negatively-related to prenatal (2nd-to-4th digits' ratio; 2D:4D) and pubertal (3rd-to-5th digits' ratio; 3D:5D) testosterone. Oxygen therapy is important in Covid-19 treatment and low 2D:4D is linked to efficient oxygen metabolism. We consider relationships between digit ratios and duration of oxygen treatment in hospitalized Covid-19 patients.

Methods: Digit lengths were measured from photographs of the patient's hands. Age, Sex, BMI, vaccination status and number of days of O₂ treatment, were recorded.

Results: There were 100 (58 women) patients. Sex differences (males<females) were present in 2D:4D ratios (Dr-l 2D:4D; ǀDr-l 2D:4Dǀ) but not in 3D:5D. Positive relationships were found between 2D:4D variables (left 2D:4D, women and men; Dr-l 2D:4D women), 3D:5D (male left 3D:5D) and duration of oxygen therapy. After removal of the influence of age, BMI, vaccination status and sex there were positive relationships between 2D:4D (right and left) and duration of oxygen therapy but no such associations for 3D:5D. In addition to 2D:4D there was evidence for a positive relationship between BMI and oxygen therapy.

Conclusion: We have found that high (feminized) 2D:4D of males and females is positively related to duration of oxygen therapy. This adds to the evidence for links between severity of Covid-19 and national and individual level variation in foetal androgen (as measured by 2D:4D). We discuss our finding in the light of the "low-androgen-driven COVID-19 pandemic theory".

Keywords: COVID-19; Digit ratio; Oxygen therapy.