Worldwide statistics show that there is a higher fatality rate in males than with females infected with the coronavirus. Scientists presume that men are less likely to wash their hands regularly, don't usually seek medical help, have genetically weaker immune systems than women, or may also have other underlying health conditions that make them more susceptible to infection.
John Manning from Swansea University alongside Bernhard Fink from Biosocial Science Information, Austria, released new information on male fatality rates in relation to the length of one's ring finger.
Before specific experiments analyzing ring and index fingers, previously available data from SARS-CoV and MERS-CoV revealed that 'males tend to generate less robust immune responses than females and are more susceptible to a variety of infectious agents.' This suggests that testosterone possibly has a negative effect in one's immune system.
The BBC Internet Study, a multi-ethnic and multi-national online survey containing 200 questions regarding sex-dependent aspects of behavior and demographics had two questions asking for the measurement of the lengths of the index finger, 2D, and the ring finger, 4D.
255,116 participants completed the survey across 41 countries. After considering some variables such as age, the study was down to 103,482 men and 83,366 women.
Coronavirus statistics in the same 41 nations showed that all deaths were between 50-72% male patients, the highest rate being in Greece. Multiple charts and graphs in the study map out how 'male right hand 2D:4D remained significantly related to percent of male deaths,' with similar results for the left hand 2D:4D as well.
Data also supported that may mean a biological advantage for those from Australia, New Zealand, Austria, and East Asian nations, where male ring fingers are longer. On the other hand, Bulgaria, Spain, and the UK had higher male fatality rates.
Testosterone Level Indicator
Carl Pintzka of the Norwegian Competence Service for Functional MRI shared that 2D:4D relationships show how much testosterone one was exposed in the womb. A longer ring finger indicates more testosterone levels in a man's body.
Professor Gülsah Gabriel of the Leibniz Institute for Experimental Virology in Hamburg added, 'of those male COVID-19 patients who died, the majority also had low testosterone levels.' He also explained that low levels of this hormone were a risk factor when an infection caused deadly 'cytokine inducing respiratory viruses.'
'The theory is that someone with high prenatal testosterone - and a long ring finger - has greater levels of ACE2,' said Manning. Large concentrations of ACE2 are enough to fight the virus.
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The Paradox of ACE2
Angiotensin-converting enzyme 2 (ACE2) is a coding protein that regulates cardiovascular and renal functions, as well as fertility. It is also a receptor of coronavirus, initially studied during the SARS-CoV breakout, and is being analyzed again with COVID-19. ACE2 is also expressed in the kidney, lung, and gastrointestinal tract.
At the same time, ACE2 is an entry receptor for SARS-CoV-2, which Manning notes in his study as a paradox. Data from their research further supports 'a link between high 2D:4D (low prenatal testosterone) and high severity of COVID-19 in men.' This means that high prenatal testosterone may protect men from the effects of coronavirus.
The study concluded that 'A strong positive association between male 2D:4D and mortality may provide a biomarker for male COVID-19 susceptibility and identify those for whom it would be advisable to exercise social distancing.'
