Reports from Italy, where the death toll from COVID-19 continues to soar, have indicated that being male is a risk factor for morbidity, alongside old age and preexisting medical conditions. The trend follows that of previous outbreaks, including the 2003 SARS coronavirus and the 1918 Spanish flu pandemic. So why does COVID-19 affect men more than women?

Italy is the second-worst affected region in the world at this stage of the SARS-CoV-2 pandemic. Since initiating a lockdown on March 9, deaths in the country have continued to rise by hundreds each day, and clinicians have noticed that men are experiencing more severe disease than women. There are more men getting infected and presenting to hospitals in Italy compared to women, and a report from the Epidemiology for Public Health shows that more men are dying and at a younger age than women.

The same trend was observed in China, where the COVID-19 outbreak first began. The Chinese Centers for Disease Control and Prevention reviewed 44,672 and found that 2.8 percent of infected men died, while the disease proved fatal in only 1.7 percent of women.

Even for children under the age of 16, gender seems to play a role in the transmission of the disease. A study reviewing 171 children and adolescents who were treated for COVID-19 at the Wuhan Children’s Hospital found boys were more likely to get infected than girls, with nearly 61 percent of their patients being male.

While it's important to note that most explanations are tantamount to speculation, one possible biological cause of the trend is that men are not as good at mounting an immune response as women, which means they suffer more severe disease as the virus takes hold. 

According to Sabra Klein, who studies sex differences in viral infections at the Johns Hopkins Bloomberg School of Public Health, this comes as no surprise. As she explained to the Independent, “This is a pattern we’ve seen with many viral infections of the respiratory tract – men can have worse outcomes. We’ve seen this with other viruses. Women fight them off better.” 

The exact cause for this difference is unknown, but it’s thought the sex hormone estrogen, which is abundant in women, likely plays a key role in immunity. There are also lots of immune-related genes coded for on the X chromosome, of which women have two while men only have one.

As well as these biological predispositions, it’s thought that lifestyle could also play an integral role. Smoking, in particular, is known to exacerbate a host of respiratory diseases. There are around 316 million adult smokers in China alone, the largest smoking population in the world according to a study published on NCBI, and around 52.1 percent of all men in China are smokers compared to just 2.7 percent of women. This presents a question for further investigation as to how gender and smoking are linked to COVID-19 morbidity. 

Statistically, more men also suffer from hypertension than women, which is another mechanism through which COVID-19 could prove more fatal for men. The CDC also states that cardiovascular disease is the leading cause of death for men, and a recent study has found that two medications used to treat different types of cardiovascular disease, ACE inhibitors and angiotensin receptor blockers, make it easier for SARS-CoV-2 to attack the lungs. Lead researcher on the study Dr James Diaz said, "Since patients treated with ACEIs and ARBS will have increased numbers of ACE2 receptors in their lungs for coronavirus S proteins to bind to, they may be at increased risk of severe disease outcomes due to SARS-CoV-2 infections."

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