Why do men suffer more from coronavirus than women?

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Most everyday illnesses don’t seem to care what gender you are: man or woman, these coughs, colds and stomach bites persist anyway.

But it is clear that COVID-19 is different. Scientists around the world report that men are much more likely to suffer from severe symptoms of the disease, which means that more will succumb.

What factors could therefore be important? The most obvious are lifestyle-related: in the United Kingdom, according to the Office of National Statistics (ONS), more men (16.5%) than women (13%) smoke. And if you are a smoker, you are already more likely to die from lung or heart disease, which would likely make recovery from COVID-19 more difficult, as these are already in the established “high risk” categories. by the NHS.

Obesity has also been linked to the toughness of the fight against Covid-19, chief epidemiologist, Professor Jean-François Delfraissy, saying that being overweight is a major risk factor for people infected with the new coronavirus. The 2017 England Health Survey found that men are more likely than women to be overweight or obese (67.2% of men compared to 61.5% of women).

Consumer habits can also be important; alcohol is a causative factor in over 60 medical conditions, including mouth, throat, stomach, liver and breast cancers; high blood pressure, cirrhosis of the liver; and depression, says Alcohol Change UK. And men drink at problematic levels more than women: figures from Public Health England indicate that among those seeking treatment for alcohol use, 60% are men.

But could something deeper happen at the cellular level? Nanotechnologist Dr. Michelle Dickinson, creator of Nanogirl STEM Adventure subscriptions, says that while the mechanisms behind gender differences are complex and certain behaviors are more visible in men (such as smoking), the way our bodies react to Covid-19 seems to turn more on immunological, hormonal and genetic factors.

“This is not the first time we have seen this difference between the sexes,” says Dr. Dickinson. “SARS, the flu, Ebola and HIV have all affected men differently from women.

“Research shows that women’s bodies are more effective at fighting infection, thanks to the hormones and many immune function genes that rely on their two X chromosomes (men only have one X chromosome). “

This means that women generally have stronger immune responses than men, except during pregnancy to help them avoid attacking their fetus. This is thought to be linked to the female hormone estrogen, which has been shown to bind to immune cells and activate disease-fighting molecules.

“When mice were infected with SARS,” says Dr. Dickinson, “male mice were more likely to die, until researchers removed the ovaries (and therefore estrogen) from female mice, after which their rate mortality was skyrocketing. “

University of New South Wales researcher Zoe Xirocostas has published a hypothesis called Unguarded X explaining why women live longer than men in general. She explains why having two matching X chromosomes (as in human women) is beneficial for longevity: “The hypothesis suggests that having a small Y chromosome (as in human men) means that you would be more likely to express unwanted traits if there was something wrong with a gene on one of your X chromosomes.

“Whereas in women having two X chromosomes means that if something goes wrong with a gene on one chromosome, you are likely to have a working version of that gene on your other X chromosome and hide (or hide) basically any mistake, and therefore not express the unwanted trait. These unwanted traits could be anything on the X chromosome. ”

For example, she said, a defective gene could play a small role in immunity or respiratory function. As explained by the hypothesis, men are more likely to express this defective gene than women (because women have an additional X chromosome which would probably have a good copy of this gene) and therefore have the function of the immune / respiratory system. in a way that is not ideal.

Normally, a small genetic error like this would go unnoticed because the body is still able to function normally, however, in the case of coronaviruses, this could be an important factor affecting how you can fight the disease.

Xirocostas also points out that testosterone has been shown to act as an immunosuppressant, which could also play a role in men who die at higher rates than women for the coronavirus.

Meanwhile, estrogen improves immune defense and acts as an antioxidant, according to a Danish analysis published in the journal PNAS in 2018, which investigated why women live longer than men, even during epidemics.

The research team led by epidemiologist Prof Virginia Zarulli points out that many infectious bacterial, viral, parasitic and fungal diseases are higher in men than in premenopausal women.

In addition, autoimmune diseases are more common in women than in men, as is a stronger immune response to vaccinations, although the mechanisms by which sex hormones affect immune responses in men have not been fully elucidated.

Can innate fitness also be important? Women treat oxygen faster than men when they start exercising, according to a 2017 study from the University of Waterloo. “We have found that the muscles of women extract oxygen more quickly from the blood, which, scientifically speaking, indicates a higher aerobic system,” said Richard Hughson, professor in the Faculty of Applied Health Sciences and holder of the Schlegel Research Chair in Vascular Aging and Brain Health at Waterloo.

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