Coronavirus: Men more vulnerable to infection than women; scientists say smoking, poor immunity could be blamed
Some say women may have a stronger immune response owing to estrogen while others say it could be because men are less likely to seek early medical care
It has been over two months since the coronavirus outbreak was first reported and a lot about the virus continues to remain a mystery.
One that stands out is figuring out why the virus strikes men more than women. Three different studies that looked at infection rates in patients found that men were more likely to have the infection.
What is more, a large study examining data from 72,314 patients found that men have a higher death rate of 2.8% compared to 1.7% in women.
This trend has raised more questions than answers. "There could be several factors involved but we don't know which ones are responsible at this point. All we know is that infected men are more likely to be hospitalized or die than women," Dr Brian Labus from University of Nevada, Las Vegas, told MEA WorldWide (MEAWW).
Like the new coronavirus, the SARS virus also targeted men. SARS is closely related to the new coronavirus, sharing 80% of its genes. A mice study suggested that the SARS virus infected male mice more than females.
Women have stronger immunity
Some scientists reason that women could have a biological upper hand. "Hormonal differences between men and women can result in different immune responses, so there may be a biological reason for the differences," explains Dr Labus.
For instance, the female sex hormone called estrogen is known to boost immunity. Additionally, women have two X chromosomes with each carrying genes related to the immune system. Men, on the other hand, have only one.
A strong immune system has its downsides. Women are more vulnerable to autoimmune disorders — 85% or more patients of multiple autoimmune diseases are seen in women, say studies.
Other factors: Smoking et al
Other scientists are leaning toward factors that are not biological.
"It might be down to the sort of men and women included in the analysis. It might be the patients’ exposure to situations that would put them at risk — it might not be an underlying biological reason," Simon Clarke, associate professor in cellular microbiology, told CNBC.
"You have to be able to exclude all sorts of other social factors to be able to say there's a real biological difference — it could be down to circumstance," he added.
Dr Labus also suspects that other factors might be at play. For example, he says, respiratory diseases often are much worse in smokers. "Over half of Chinese men smoke while only about 1% of Chinese women do. Smoking is also more common in China in older people than younger people," he explains.
A recent study that analyzed information from the first 8,000 cases in China also suspected that smoking could be putting men at risk of death.
Further, scientists believe that the male-female bias could be due to the jobs they hold. Men are also more likely to work in industrial occupations that may expose them to lung-damaging chemicals, according to Dr Labus.
Another factor could simply be due to a lax attitude toward health.
Dr Labus said: "Men are also less likely to seek medical care early in the course of illness, so it may be a case of men not receiving care early in the infection. It is likely to be a combination of these factors that lead to higher death rates in men.
Those who delay getting medical help have a higher risk of death. Supporting this idea is a study on 4,021 patients infected with COVID-19. The researchers found that men are seeking medical help only when the disease goes out of hand.
Men may have a "false sense of security" when it comes to the coronavirus, Akiko Iwasaki, a professor of immunology at Yale University, told the New York Times. Iwasaki studies why some viruses affect women more severely.
According to Dr Labus, most diseases we see affect men and women equally at the biological level. "The real differences are in our behaviors," Dr Labus added.