A new study led by Swansea University has found a link between finger length and the likelihood of developing severe Covid-19.
The study, led by Professor John Manning, examines the link between testosterone and Covid-19 severity more closely by looking at how long your fingers are.
In general, men have longer ring fingers than index fingers due to higher levels of prenatal testosterone, whereas women have the opposite as a result of higher levels of oestrogen. Another indicator of low testosterone in puberty in particular is a shorter pinky or little finger relative to the middle finger. You can get more Swansea news and other story updates by subscribing to our newsletters here.
Read more: What the lengths of two of your fingers tell you about you and your mum according to new study
The new study found that a longer index finger relative to the ring finger indicated an elevated risk of Covid-19 hospitalisation, suggesting low testosterone both prenatally and in puberty. It also found that hospitalized patients with Covid-19 had short pinky fingers compared to their other fingers, which suggests low testosterone during puberty.
Professor John Manning, of the A-STEM research team, said: "Men who are hospitalized with Covid-19 tend to have very low testosterone and high oestrogen. In humans, patterns of digit length give us clues as to testosterone levels during development, both in the womb and in puberty.
"A long index finger (2D) relative to ring finger (4D) indicates low testosterone in the womb and a short little finger (5D) relative to the middle finger (3D) may indicate low testosterone in puberty. Both are more common in women than in men. In addition, there may be differences in these ratios between right and left hands, and these differences tend to be higher in women.
"We have found that in comparison to healthy controls, hospitalized patients with COVID-19 have (i) short little fingers compared to their other fingers (suggesting low testosterone during puberty), and (ii) the differences in right and left hand ratios are substantially higher, particularly for the index finger relative to the ring finger and for the little finger relative to the other fingers (suggesting low testosterone prenatally and in puberty).
"The patterns of 'female-type' digit ratios in patients hospitalized for COVID-19 suggest that the testosterone-depression and oestrogen-elevation caused by the virus is strong in individuals with 'feminized' ratios. The effects of this may be particularly problematic in men."
The professor added that low testosterone and high oestrogen prenatally and at puberty had been linked to other conditions such as obesity and heart disease in men, adding: "Covid-19 is potentially more serious in patients suffering from these pre-conditions. "
This isn't the first study led by Professor Manning linking finger length to health, either. In 2021, Swansea University published research that highlighted how the length of children's fingers related to mothers' income levels and pointed to susceptibility to diseases that began in the womb.
The study revealed that low-income mothers might feminize their children in the womb by adjusting their hormones, unbeknown to them, whereas high-income mothers masculinize their offspring. Professor Manning said the team's work would now continue: "The sample is small but ongoing work has increased the sample. We hope to report further results shortly."
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