Covid-19 is similar in important ways to the diseases caused by other recent coronaviruses, such as SARS and MERS. Like Covid-19, SARS and MERS exhibited male-female differences in fatalities. As with Covid-19, this difference was initially claimed as a “sex” difference. But careful analysis showed that gendered behaviors, pre-existing conditions, and gender-segregated occupational exposures explained these sex differences. All signs point to Covid-19 following a comparable pattern.
SARS emerged in early 2003 and quickly reached pandemic levels. Men overall indeed died at a higher rate than women. But a closer inspection of the data soon showed that sex differences varied considerably by age group. At older ages, there was no significant difference between the female and male fatality rates, but younger men died at markedly higher rates than younger women. For instance, in Hong Kong, only 5.9 percent of women ages 35 to 44 died, compared with 15.3 percent of men. Between the ages of 35 and 64, men who developed SARS were 10 percent more likely to die than women.
Taking a cue from these patterns, researchers ran analyses accounting for age, occupation and pre-existing conditions. The results showed that after accounting for these factors, women and men actually had similar fatality rates for SARS for all age groups. The lower fatality rate among women was driven by particularly high infection rates among health care workers, who were predominantly young, healthy and female. So women were both disproportionately likely to be infected and disproportionately likely to survive, compared with men in that age group. Among older women and men, and those with comorbidities such as heart disease, cancer, asthma and liver disease, there was little difference in SARS outcomes. The apparent sex difference was caused by gender-related occupational differences and diseases with complex, often socially rooted causes.
MERS offers an even more clear-cut example. The disease overwhelmingly affected, and continues to affect, older men. Primary transmission from camels remains a key source of infections, and camel handling and slaughtering are predominantly male occupations in Saudi Arabia. As with SARS, a comprehensive study published in 2017 found that fatalities did not differ by sex after accounting for age and pre-existing health status. The sex difference here, in other words, is produced by who is getting infected, not who dies once they’re infected.
A key factor most likely related to male-female differences in Covid-19 fatalities is that men overall are in a poorer state of health than women. In a study examining sex differences in outcomes among Covid-19 patients in China, men were more likely than women to have any comorbidity or two or more of them. Of people with Covid-19 and chronic obstructive pulmonary disease, 83.3 percent were male. Of people with diabetes and cardiovascular disease, 58.9 percent and 62.1 percent, respectively, were male. To be sure, sex-linked biology may play a role in the development of some chronic diseases, but always in complex interaction with class, race or ethnicity, and gender-related variables. Several analyses have already demonstrated that in places where men have higher Covid-19 fatality rates than women, men also, on average, have far higher rates of behaviors such as smoking and comorbidities related to smoking, such as heart disease.