By Aria Bendix -
NBC News
It is one of the mysteries of the pandemic: Why have men died of COVID-19 in greater proportion than women?
The death rate from coronavirus in men is 1.7 times higher on average than that of women in 38 countries, according to a 2020 study. More recent research by scientists at Harvard University found that while men make up 49% of COVID-19 cases in the United States, were 55% of deaths from April 2020 to May 2021.
This week, another study pushed the leading theory behind this discrepancy:
Estrogens may offer some protection against severe coronavirus disease.
Doctors treat a patient infected with COVID-19.Getty Images
For the study, published in the British journal Family Practice, researchers looked at women who had received hormone replacement therapy - which helps restore estrogen levels in menopause - within six months of their COVID-19 diagnosis.
Results showed they had a 78% lower all-cause mortality rate than women who did not receive such therapy.
The study involved more than 5,400 women, most of them white and of menopausal age (about 59 years old on average).
The researchers also took into account socioeconomic status and pre-existing health problems.
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"This adds to the body of evidence as to why, especially early in the pandemic, we see really different clinical outcomes in women and men," said Anita Raj, a professor of infectious diseases and global public health at the University of California, San Francisco. Diego, who did not participate in the investigation.
Although the study's relative homogeneity is a limitation, he said, its conclusion still "appears to be in line with the notion that it is estrogens specifically that are protective."
Can balance the immune response
Other hypotheses have been considered to explain the difference in mortality in the last two years.
In the Harvard study, the researchers suggested that the types of jobs women hold most often and their behavioral tendencies might have an effect.
In the US, for example, women are more likely to say they are wearing masks and social distancing, while men are more likely to be involved in jobs that expose them to the virus.
But experts say it makes sense that estrogen could play a protective role against COVID-19, since the hormone is known to stimulate an immune response by producing antibodies.
At the same time, higher levels of estrogen can prevent the immune system from responding too aggressively to a viral infection, which can lead to life-threatening inflammation.
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"We see that women have a faster and higher antibody response to COVID-19 infection, which probably means they can clear the infection more quickly than men," said Christopher Wilcox, co-author of the new study and clinical fellow. academic from the University of Southampton.
Wilcox added that "a number of studies have shown that higher estrogen levels appear to be associated with less severity of infectious disease in general."
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A 2016 lab study, for example, suggested that estrogen prevented the flu virus from replicating in cells.
And other research has shown that estrogen can prevent HIV, Ebola, and hepatitis from replicating, too.
The new research also aligns with a 2020 study that found hormone replacement therapy halved the risk of coronavirus mortality among women over 50.
However, that research did not find a difference among premenopausal women.
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For this and many other reasons, experts say it is unknown whether estrogens might be useful as part of a preventive therapy or treatment regimen for COVID-19.
Hormone replacement therapy carries its own risks, as long-term use can increase your chances of having a stroke, blood clots, or heart attack.
“Estrogen prescription carries some risks, but is it something that deserves further study?
Yeah, definitely," Raj said.
At least, according to Wilcox, his study suggests that women who get COVID-19 don't need to stop their hormone therapy.