Men Might Recover Faster From Flu Than Women Thanks to a Special Molecule, Study Suggests

Men might recover faster from the flu because they produce more of a protein which the body uses to heal the lungs, according to a study.

Researchers at Johns Hopkins Bloomberg School of Public Health believe men produce more amphiregulin, a protein which is vital for mending tissue.

The scientists investigated whether men and women heal differently by conducting experiments on mice and human tissue.

In one part of the study, they infected mice with H1N1, a strain of flu which caused an outbreak in 2009 and killed more than 18,000 people worldwide. Male and female mice took around the same time to be clear of the virus, but the difference came down to recovery.

Females lost more weight and experienced worse lung inflammation when the infection was at its peak. They also took longer to regain normal lung function.

The team also found the male mice produced significantly higher levels of amphiregulin than females as they recovered from the flu.

And when male mice were genetically engineered to not produce amphiregulin, their recovery mirrored the females' more closely. But females genetically engineered in the same way did not differ that much from the control group.

For the next part of the study, the scientists infected human lung epithelial cells—which provide a first line of defense against bacteria and viruses—with flu. The amount of amphiregulin cells created subsequently spiked, but only in samples from males.

The researchers published their paper in the journal Biology of Sex Differences.

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Dr. Sabra Klein, an associate professor in molecular microbiology and immunology at the Bloomberg School, told Newsweek: "We are showing for the first time that the sexes differ in the repair of damaged lung tissue following flu infection. Specifically, that males repair tissue faster than females.

"What is new is that we also identified the growth factor responsible for this repair, amphiregulin. This a protein made by epithelial cells as well as different types of immune cells. We also showed that the epithelial cells in the lungs of both humans and mice produce amphiregulin following infection and if these cells come from males, then they produce more amphiregulin after flu infection than do cells from females."

A 2016 study carried out by the team suggested the sex hormone progesterone—which is involved in processes such as menstrual cycle and pregnancy—stimulates the production of amphiregulin in female mice.

Their results are a step forward for creating new treatments for severe flu, which could one day see levels of amphiregulin in women boosted.

"A future direction of this research would be to see if oral contraceptives could improve the outcome of flu infections by increasing production of the growth factor, amphregulin," said Klein.

Next, researchers hope to understand why males create more amphiregulin when they are sick with the flu. The team initially believed the answer was testosterone levels, but later concluded the hormone doesn't appear to affect the production of amphiregulin.

Professor Helen Stokes-Lampard, chair of the U.K.'s Royal College of General Practitioners, told Newsweek: "While these findings make for interesting reading, we have known for some time that regardless of a patient's sex, people experience flu differently and therefore recover at different rates depending on a number of complex factors."

Elderly patients, she said, are more susceptible to the flu and less likely to recover quickly, compared to a younger person.

"Irrespective of these factors, however, anyone who thinks they have the flu should get plenty of rest, stay hydrated, and ease their symptoms with over-the-counter medication like paracetamol and ibuprofen.

"Patients who are particularly worried about their symptoms should seek advice from their local pharmacist or other healthcare professional."

Dr. Steve Holmes, medical doctor and adviser at the British Lung Foundation, told Newsweek: "Being struck down with 'man flu' can often lead to many arguments between couples, but this study brings new evidence that suggests that women might actually be worse affected by flu.

"If a similar pattern of amphiregulin production can be duplicated in humans, then we might see new treatments that help produce more of it in our bodies, which may help us all recover faster and make 'man flu' a thing of the past."

In the U.S., the winter spanning 2017 and 2018 marked the worst flu season for over a decade with higher than normal levels of people being hospitalized across the country, according to the Centers for Disease Control and Prevention.

Starting in November, the season reached its peak during January, February and into March.

This article has been updated with comment from Dr. Sabra Klein​, Professor Helen Stokes-Lampard and Dr. Steve Holmes.