The novel coronavirus seems to be killing more men than women.
The trend was first noticed in China, experts say, and the higher COVID-19 death rate for men has since been documented in 33 countries, including Germany, Spain and South Korea. But experts don’t know what’s causing the gap. Is it biological, some quirk of cells and hormones? Is it the result of gendered behaviors that have more to do with sociology than sex chromosomes? Let’s break down what’s going on, because experts say men’s risk level depends on what risks (and which men) you’re talking about.
What we know
While men account for the majority of COVID-19 cases in some countries but a minority of cases in others, they consistently make up the majority of deaths. Out of 35 countries that have reported their COVID deaths in ways that break out victims by sex, 33 had a male-female death ratio greater than 1, meaning men who were confirmed to have the disease were more likely to die than women who were confirmed to have it, according to data compiled by Global Health 50/50, a independent health equity research organization based at University College London. “So far, the mortality disadvantage for men is quite large,” said Jennifer Dowd, a professor of demography and population health at the University of Oxford
This dynamic isn’t new to medicine. “Women have stronger adaptive immune responses and die less of infectious disease their entire lives, starting from infant mortality,” Dowd said. In general, women’s bodies kick out bacterial and viral invaders faster than men’s do, and vaccines work better for women than for men.
To see why, look to hormones and genetics, said Sabra Klein, professor of microbiology and immunology at Johns Hopkins University. Sex hormones appear to play a role determining how well human bodies can fight off disease. In general, estrogens amp up the immune system, while androgens (like testosterone) and progesterone suppress it. Hormones have to interact with cells to do their jobs, Klein said, so cells have a “lock” and hormones have the “key” to get in. And, turns out, every immune cell in your body has these kinds of lock-and-key receptors.
Sex chromosomes also play a role. The X chromosome, for example, has 60 genes associated with immune function. Most biological males are born with one X chromosome, but those immune-boosting genes tend to be expressed more frequently in women, who generally have two X chromosomes, Klein said.
But if you’re tempted to think those sex differences boil down to “men are more likely to die from infectious disease,” Klein cautioned that the generalization is not true across the board. Sex differentiation in influenza has been pretty well studied, she told me, and, in that case, women’s more aggressive immune systems don’t give us an advantage. Having too much of an inflammatory immune response to the flu can actually increase your risk of complications — including acute respiratory distress syndrome, when the lungs’ tiny air sacs, called alveoli, are damaged and fill with fluid. “Reproductive-age women do worse, not better,” Klein said.
What we know we don’t know
But while researchers know a decent amount about sex differences in influenza, the novel coronavirus is, yes, novel. Any research on it is a work in progress, proceeding without full data. That starts with basic documentation.
On April 28th, the United States had reported 57,318 deaths from the novel coronavirus, but only 31,586 of those deaths had been reported in ways that allowed Global Health 50/50 to break them down by sex. None of the researchers I spoke with knew why that data isn’t getting reported. But without it, they’re left to a lot of guesswork and speculation. It’s safe to assume that deaths in the U.S. are probably following the patterns seen in many other countries — but we don’t know for sure that that’s true.
Then there’s the fact that the variations in how this virus affects people probably isn’t just about what’s in their chromosomes or hormones. It’s also about sociological gender — the attitudes, stereotypes and norms that shape the ways people behave and the choices they make.
For example, a 2016 meta-analysis showed that women are about 50 percent more likely than men to start using non-pharmaceutical protective behaviors during a pandemic — things like wearing face masks or avoiding public transit. Men, meanwhile, were about 12 percent more likely than women to sign up for vaccines, take antiviral medication, or use other pharmaceutical interventions. Those differences in behavior aren’t determined by biology, but they could help create variations in how a virus affects men and women.
Rosemary Morgan, a scientist at Johns Hopkins Bloomberg School of Public Health who studies how gender and sex interact with public health, thinks these kinds of effects are happening with COVID-19. But how and to what extent — that’s unknown. It also probably differs from country to country, thanks to the way gender norms also aren’t consistent everywhere you go.
Case in point: When data on sex disparities in COVID-19 deaths first began to come in from China, it wasn’t clear that the differences in death rates there would mean other counties were going to experience the same thing. That’s because China has particularly gendered smoking habits, Dowd told me. In a 2010 study, 54 percent of Chinese men surveyed were current smokers. In contrast, the same study found that less than 3 percent of Chinese women currently smoked. Although sex differences in COVID-19 death rates have cropped up again in other countries, it’s likely that this gender disparity in smoking plays a role in why 64 percent of China’s COVID-19 deaths have been among men even though men account for right around half of China’s confirmed cases.
Gender norms may also influence the niches where women are getting the disease more than men, despite men’s higher death rates. When the Centers for Disease Control and Prevention looked at the characteristics of health care workers who have contracted COVID-19, it found that 73 percent were women. Why are female health care workers getting infected at much higher rates? Part of it likely has to do with their higher odds of exposure.
Nurses’ jobs put them in close physical contact with patients who have COVID-19 and other infectious diseases, and more than 70 percent of nurses are women. Meanwhile, the personal protective equipment meant to help keep medical workers safe often isn’t designed with women in mind. Gloves can be too large. Masks don’t always fit women’s faces with a tight seal. Gender dynamics could be putting a largely female workforce in harm’s way.
In the end, regardless of your sex — or your gender — the risks you face from COVID-19 are probably somewhat unique to you. But if we want to figure out just what, exactly, those risks are, we’re going to need more data.