Men and the Flu: Are We Really the Stronger Sex?

The image of the sniffling, sneezing man, wrapped in a bathrobe, and being waited on by his long-suffering-but-perfectly healthy wife is always good for a few chuckles and snorts about how women are actually the stronger sex. And, although most guys don’t want to admit it, when it comes to fighting off colds, the flu, and pretty much any bacterial, fungal, viral, or parasitic infection, there’s some science to back up those chuckles and snorts.

In fact, scientists have known for years that men’s immune systems aren’t as hardy as women’s, but they never understood why. A team of researchers from Stanford University may have just answered that question—at least partly—and the culprit may be the one thing that makes men men.

The researchers, including Mark Davis, professor of microbiology and immunology at Stanford, found that “men with relatively high amounts of circulating testosterone benefit less, as measured by a boost in protective antibodies after vaccination against influenza, than do men with lower testosterone levels and women.” Put a little differently, the flu vaccine is more effective for women than for men, but guys with “relatively low testosterone levels” respond just as well as women.

Actually, it’s not testosterone itself that’s the problem, it’s the way the hormone interacts with genes in a way that keeps the immune system from kicking into high gear. Either way, if you’re doing any kind of testosterone supplementing, you should talk to your doctor about whether the benefits outweigh the increased risk of getting the flu—and taking longer to recover.

Mark Davis has spent quite a bit of time trying to figure out why Mother Nature (maybe that’s the answer right there) would design a hormone that increases muscle strength and other male characteristics but leaves men more susceptible to infection. Clearly, there must be some kind of evolutionary advantage to a weakened immune system, otherwise men have been wiped out long ago. It’s a fascinating question, and Davis suspects that in some circumstances, a weaker immune system is actually a good thing. Here’s what he thinks: Men are prone to suffer wounds from their competitive encounters, not to mention from their traditional roles in hunting, defending kin and hauling things around. Those wounds increase men’s infection risk. However, while a strong immune response is usually a good thing, when the system overreacts—which it does when it encounters highly virulent influenza strains, SARS, dengue and many other diseases—the result can be worse than the actual disease. He points out that women, even with their robust immune responses, are twice as likely as men to die from sepsis, which is essentially an immune system run amok.

Davis, who is also the director of Stanford’s Institute for Immunity, Transplantation and Infection, proposes that “having a somewhat weakened (but not too weak) immune system can prove more lifesaving than life-threatening for a dominant male in the prime of life.”

Bottom line: if you haven’t had a flu shot, get one—your immune system needs all the help it can get. And again, talk with your doctor about the risks vs. rewards of testosterone supplementing.

This study was published in the Proceedings of the National Academy of Sciences. Read a press release about it here.