A Canadian researcher says there is some evidence that hormones and other factors may make men more susceptible to serious cases of the flu.
In an environment in which men are being vilified for abusing their power, it’s hard to know what to make of the latest developments in the so-called “man flu.”
Those define the illness as a cold or similar minor ailment in which the sick man is accused of exaggerating the severity of the symptoms.
The latest study germinated when a Canadian researcher got sick, then got inspired.
Dr. Kyle Sue, clinical assistant professor in family medicine at the Health Sciences Centre at Memorial University of Newfoundland in Canada, found himself flat on his back when a cold turned into the flu.
That’s when he thought the subject of “man flu” could stand a little investigating.
“The studies are not definitive, but they are suggestive,” Sue told Healthline.
“We do know that men and women have differences in their immunity systems,” he said. “The higher the testosterone level, the less powerful the immune system.”
“It’s a common stereotype,” Sue said. “When women are sick, they still juggle their chores at home with work, whereas men plop down on the couch. Are women more resilient?”
Sue examined several centuries’ worth of study on mice and men.
The records dated back to William Harvey in 17th century England.
A number of studies demonstrated higher immune responses in female mice.
“This led to the hypothesis that sex-dependent hormones have an important role in outcomes of influenza,” Sue said in his paper.
Another study looked at mononuclear cells from 63 healthy people divided into groups by age and gender.
The cells were then exposed to a rhinovirus.
Cells cultured from premenopausal women had a stronger immune response to rhinovirus than those from men of the same age.
This difference was not observed when postmenopausal women were compared with men of the same age, suggesting a hormonal link.
But “suggested links” are not scientific conclusions, Sue noted.
The sex difference in immunity rates may be modified by hormonal differences, with testosterone being immunosuppressive.
However, the reviewed studies did not consider other differences between the sexes — for example, men have higher rates of smoking worldwide and are less likely to take preventive care or seek treatment when ill.
Hormonal influence on immune response is supported by evidence that pregnant women have more severe influenza symptoms and reduced symptoms from autoimmune diseases than nonpregnant women.
However, it is unclear how this is mediated or might apply to a difference between the sexes, given the stressors that occur during pregnancy.
If the differences found in these studies are real, the evolutionary purpose of men’s higher rate of symptoms from viral respiratory infections remains unclear.
One suggestion: If males require testosterone for aggressive behavior and the development of secondary sexual characteristics, these needs may override the cost of any immunosuppressive effects of the hormone.
Likewise, the authors of another study speculate that reduced immunity is less important for men because males of many species are more likely to die from trauma before an infection kills them.
Sue himself tends to believe that it’s unfair to fling the accusatory “man flu” around as if it were somehow dirty.
“Men may not be exaggerating symptoms but have weaker immune responses to viral respiratory viruses, leading to greater morbidity and mortality than seen in women,” he wrote in his study.
Although Sue’s work was intended as light holiday reading, other researchers have tossed their hats in the ring.
Sabra L. Klein, for one.
Klein, PhD, is an associate professor at Johns Hopkins University Bloomberg School of Public Health and she shared her opinion on CNN.
She was not involved in Sue’s study, but she appreciates his attempt to shed light on gender health differences. These, she said, “often are ignored.”
“When we hear ‘man flu,’ we assume this means all males of all ages,” Klein said. “This is not true.”
Rates of hospitalization are consistently higher for young (prepubescent) and old (over 65) males, she said.
During the reproductive years, it is women who often suffer more severe disease, in part because flu is worse for pregnant women, but also because women develop higher — almost excessive — inflammatory responses to flu.
“The point I want to make is that whether males or females suffer more really depends a lot on our age,” said Klein.
In parts of the world where women have less access to healthcare or treatments, or where boys are more valued than girls, it may appear that boys and men are being hospitalized at higher rates.
“These unfortunate facts create biases in our interpretation of data,” Klein said. “In my opinion, we do not yet have enough science to conclude that ‘man flu’ is real.”