Coronavirus: Why does COVID-19 pose a greater threat to men than women?

As coronavirus continues to spread across the globe, it remains clear it is a disease that pays no attention to borders, race or nationality.

However, with daily updates on infection rates and death tolls, it appears COVID-19 does pose a noticeably bigger threat to men than it does to women.

These figures by no means tell the full story - mainly because the coronavirus outbreak is still in its early stages and because of the different ways nations are collecting figures.

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But also because only a handful are collating sex-disaggregated data.

Data collected from other similar outbreaks - severe acute respiratory syndrome in Hong Kong (SARS) and Middle East respiratory syndrome (MERS) - have also shown men are more severely affected.

Global Health 50/50 has been collecting COVID-19 infection figures from the 25 countries with the highest number of cases.

Of those, 11 give details on male and female fatality: Italy, China, Germany, Spain, Iran, South Korea, France, the Netherlands, Portugal, Denmark and Sweden.

And from these, 68% of those who die after contracting the virus are male with China (71%) and Portugal (70%) topping the list (figures updated 25 March).

But why does coronavirus appear to pose a greater threat to men?

Chronic illness

Many victims of COVID-19 have been suffering from underlying health conditions such as heart disease, stroke, lung disease and hypertension.

These conditions affect more men than women according to a study published in the Lancet medical journal in 2018 .

Lifestyle

Levels of smoking and alcohol consumption among men is higher than women according to a recent study by the World Bank and the World Health Organisation (WHO).

These habits are associated with the risk of developing the underlying health issues that pose a greater risk for those with coronavirus .

Natural immunity

Previous research has revealed that men have lower innate antiviral immune responses to a range of infections including hepatitis C and HIV. Studies in animals have also suggested this may also be true for other forms of coronavirus.

Hormones are also believed to play a major role with oestrogen being shown to increase antiviral responses of immune cells. Scientists have also discovered many genes that regulate the immune system are encoded on the X chromosome (of which men have one, and women have two).

Sarah Hawkes, professor of global public health at University College London (UCL) and co-director of Global Health 50/50, has said we will only be able to get a clearer picture when sex-disaggregated data is more widely available.

She told CNN: "If I was designing clinical guidelines, I would very much want to understand why some people seem to have a much higher risk of mortality than others.

"It might for example lead to a difference in the way in which we administer clinical guidelines amongst people who have pre-existing health conditions that lead to risk of death along with those with chronic lung disease, who are more likely to be men."