And why the sex differences in Covid-19 susceptibility?

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Most day-to-day diseases don’t seem to care what sex you are: man or woman, those coughs, colds and stomach bugs latch on regardless. But, says a report in The Daily Telegraph, there’s clear evidence that COVID-19 is different. Across the world, scientists are reporting that men are much more likely to suffer severe symptoms from the illness, meaning more will succumb.

So, the report asks what factors could be important? The most obvious are lifestyle-related: in the UK, according to the Office of National Statistics (ONS), more men (16.5%) than women (13%) still smoke. And if you’re a smoker, you’re already more likely to die from lung or heart disease, which would likely make recovery from COVID-19 more difficult as these are already on the ‘high risk’ categories established by the NHS.

Obesity has also been linked to how hard COVID-19 can hit, with France‘s chief epidemiologist Professor Jean-François Delfraissy saying being overweight is a major risk factor for people infected with the novel coronavirus. The Health Survey for England 2017 reported that men are more likely than women to be overweight or obese (67.2% of men compared to 61.5% of women).

The report says drinking habits might matter too; alcohol is a causal factor in more than 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: Public Health England figures state that of those seeking treatment for alcohol use, 60% are men.

But, the report asks, could something deeper be going on at a cellular level? Nano-technologist Dr Michelle Dickinson, creator of Nanogirl STEM Adventure subscriptions, says that while mechanisms that underlie differences between the sexes are complex and there are some behaviours seen more in men (such as smoking), how our bodies react to Covid-19 seems to revolve more around immunological, hormonal, and genetic factors. “This is not the first time we have seen this gender difference,” says Dickinson.

“SARS, influenza, Ebola and HIV have all affected men differently to women. Research shows that women’s bodies are better at fighting off infection, thanks to hormones and the many immune function genes that sit on their two X chromosomes (men only have 1 X chromosome).”

Meanwhile oestrogen enhances immune defence and acts as an antioxidant, says a Danish analysis, which looked into why women live longer than men even during epidemics.

Could innate fitness also matter? Women process oxygen more quickly than men when they start to exercise, according to a 2017 study from the University of Waterloo. “We found that women’s muscles extract oxygen from the blood faster, which, scientifically speaking, indicates a superior aerobic system,” said Richard Hughson, a professor in the faculty of applied health sciences, and Schlegel research chair in vascular ageing and brain health at Waterloo. By processing oxygen faster, women are less likely to accumulate molecules linked with muscle fatigue, effort perception and poor athletic performance.

Another factor where gender matters is a protein called ACE2. Dickinson explains: “COVID-19 prefers to infect and latch on to cells that have this ACE2 protein on the outside. Recent (though not peer reviewed) research on COVID-19 infected patients in China showed higher circulating ACE2 levels in men than in women and in patients with diabetes or cardiovascular diseases.

“While there is still more research to be done, it does seem that females are designed to have a more robust immune response to COVID-19.”

Full report in The Daily Telegraph

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