(CN) — Men who contract Covid-19 have a higher risk of dying than women who get the virus, according to a newly released analysis of cases in China.
In research published by the journal Frontiers in Public Health Tuesday, Chinese researchers said that although men and women have the same prevalence of Covid-19, men have a higher mortality. The scientists said that male gender is a risk factor for worse outcomes from the virus “independent of age” and comorbidities.
Other scientists support such findings but have struggled to figure out the underlying causes for such a difference in the way the virus appears to affect men versus women.
One challenge is figuring out which factors are connected to biology and which are connected to socio-cultural norms, according to Dr. Marcia Stefanick, a professor of medicine at the Stanford Prevention Research Center.
“We do know that women in general have a more robust immune system and that’s been well established, so they take the vaccinations better, they fight infections better,” Stefanick said. “Women have two X chromosomes and the X chromosome has a lot of antibody/immune system genes on it so if you have two of them, then you have a different immune system.”
Others have postulated higher levels of estrogen in women or higher rates of smoking among men could be a contributing factor but Stefanick said there is not enough data to support either hypothesis.
“We just don’t have the population data that we need to tease apart the kind of confounding factors that we usually want to look at when we’re trying to figure this out,” Stefanick said.
Another lead put forward by the team of researchers in China hones in on the ACE2 receptor, which the virus attacks. Many researchers have drawn comparisons between related severe acute respiratory syndrome coronaviruses SARS-CoV-2 of 2003 and SARS-CoV-2, which caused the current pandemic. Both coronaviruses attack the respiratory system and infect cells via the ACE2 receptor.
Higher levels of ACE2 receptors have been measured among three groups of people who tend to suffer adverse Covid-19 symptoms at higher rates: men, and individuals with diabetes or heart disease.
“We have previously reported that high protein expression of ACE2 receptor in specific organs correlated with specific organ failures indicated by corresponding clinical parameters in SARS patients. It has been shown that circulating ACE2 levels are higher in men than in women and in patients with diabetes or cardiovascular diseases,” explains the research paper, drafted by Dr. Jin-Kui Yang from the Beijing Tongren Hospital.
Based on data collected in China Jan. 29 to Feb. 15, the team calculated the male to female mortality as 2.4 to 1, although the rate of infection is equal between sexes. Most countries have since documented a similar disparity in the mortality rates of genders but the ratio differs from place to place.
Research organization Global Health 50/50 is collecting and publishing data on the gender disparity associated with Covid-19. The website’s current estimate for China indicates men are 1.7 times more likely to die from Covid-19 than women. The disparity is highest in Thailand where an estimated 3.8 men die for every woman, but the disparity is significantly lower in Canada and Iran.
According to the site, the trend is reversed in India and Pakistan where .9 men die from Covid-19 for every woman.
These statistics are only as good as the testing that occurs and is reported and may also be indicative of the people who have access to health care. Global Health 50/50 only has enough data to break down infection mortality by gender for 30 countries.
“Men of all ages need to be aware that, just like heart disease or diabetes, their sex is a potential risk factor,” said Summer Johnson McGee, dean for the University of New Haven’s School of Health Sciences.
“This should be a wake-up call to men that it is even more important for them to wash their hands, abide by social distancing, and wear protective face coverings,” McGee added. “Men who are the designated errand runners for their households should think twice as their exposure is much more risky, statistically speaking.”