The coronavirus has no geographical boundaries but seems to have gender-based preferences. More men die than women do: so why is this?
In an article dating from June 2019, we dealt with a topic that usually provokes discussion: the difference between men and women; obviously from an overall health perspective, or more accurately, from a diagnosis and treatment point of view. In that article, it was made abundantly clear that there are certain diseases that affect men more, and others women.
How does SARS-CoV-2 behave?
According to data analyzed in China and recently published in the Chinese Journal of Epidemiology, the mortality rate of coronavirus-infected people is 2.8% for men and 1.7% for women. In Italy, there is this same trend. Moreover, in Italy men are also more infected than women are. From the data available from STATISTA, the cases of COVID-19 are divided between 55.7% for men and 44.4% for women.
This trend had already been observed during previous SARS outbreaks in 2003 and MERS in 2012. Subsequently, in 2017, American and German researchers investigated the susceptibility to SARS infection in mice, and they found increased infectious capacity of the virus in males, as well as increased incidence of mortality.
What are the causes of the difference in susceptibility to infection between the sexes?
First of all, we must specify that the highest mortality rate belongs to the elderly age group (over 70 years). There are no specific data available to date on the under 70-age group. Several hypotheses have been formed that can help explain the reasons for the different susceptibility to infection and mortality, and they are as follows:
Hormones – it’s widely known that estrogen (female hormones) can provide some immune system protection. The reason is that women, biologically structured for child bearing, must also protect unborn babies; they do so with a more efficient system of antibody production. However, this hypothesis contrasts with the age of the most affected group. In fact, in older women, the production of estrogen is reduced and therefore the effect should be less.
X Chromosomes – in X chromosomes (also referred to as sex-determining chromosomes), there are immuno-related genes. Men have one X chromosome and one Y chromosome and women have two X chromosomes; therefore, twice as many immune-related genes. This characteristic provides women a greater capacity to produce antibodies and could, in part, compensate for the decrease in the effectiveness of estrogen experienced in old age.
Smoking – in many cultures, men smoke more than women. In China, where the largest study of susceptibility to SARS-CoV-2 has been performed, 50% of men smoke and only 3% of women. It’s known that smokers may be more than twice as likely to require intensive care or artificial respiration, as they develop chronic bronchitis over time; which severely restricts breathing capacity and reduces lung elasticity.
Other Diseases – mortality is also associated with the presence of other diseases such as diabetes and hypertension, which, at least in China, have a higher incidence in men than in women.
The data speak for themselves: COVID-19 is more aggressive in men
In conclusion, available data show that both susceptibility to SARS-CoV-2 infection and mortality in the 70 and-above age group is higher in men than in women.
These data (at present mainly from studies of the general Asian population) can be taken as a reference but need to be confirmed by research on European populations – that differ significantly in lifestyle.
This post is also available in: Italiano