Lydia Wang ’26
SARS-CoV-2 is a virus that attacks the respiratory system, causing the disease COVID-19. The disease’s severity and risk factors have been shown to vary across certain populations. In particular, COVID-19 mortality rates were observed to be significantly higher in males than in females. One possible explanation for this cites testosterone levels, which have been seen to correlate with the ratio of digit (finger) lengths. A team of researchers led by Anna Kasielska-Trojan of the Medical University of Łódź sought to further understand this possible relationship between digit ratios and the severity of COVID-19. Kasielska-Trojan et al. hypothesized that patients experiencing more severe COVID-19 would have larger ratios in both hands, high asymmetry, and that the ratios between the second and fourth digit (2D:4D) and the third and fifth digit (3D:5D) would be important to consider because they are most indicative of developmental instabilities, which are more common among patients hospitalized for COVID-19.
For this study, 54 participants who were hospitalized from COVID-19 were recruited, alongside a control group comprising 100 participants with no history of COVID-19. Participants were given a clinical questionnaire and had the severity of their conditions noted. To prevent spread of the virus, digits were photographed and measurements were taken using various computer programs. The second, third, fourth, and fifth digit on each hand were photographed, leading to a total of eight measurements; ratios between all the digits’ lengths were then determined. The Clinical Composite Asymmetry was also measured, which looked at the 2D:4D and 3D:5D ratios. No significant differences in digit ratios were observed between different age or sex groups. However, the Clinical Composite Asymmetry was observed to correlate positively with a higher risk of more severe COVID-19. Additionally, it was suggested that ratios involving the fifth digit might be indicative of developmental instability, and therefore could be negatively correlated with immune system function.
The results of this study connect physical manifestations of developmental instabilities with higher risk for severe cases of COVID-19, providing additional insight into COVID-19-related health threats and societal circumstances; a greater understanding of the nuances and effects of socioeconomic status and comorbidities can provide background of individuals’ circumstances that may impact susceptibility. In the future, evaluating a larger number of patients, increasing racial diversity among participants, and using higher quality photos may result in more generalizable and accurate results.
 A. Kasielska-Trojan, et al., Digit ratios and their asymmetries as risk factors of developmental instability and hospitalization for COVID-19. Scientific Reports 12, 4573 (2022). doi: 10.1038/s41598-022-08646-7.
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