Although there is no clear gender pattern in terms of susceptibility to Covid-19, once infected, men have consistently been shown to have higher fatality rates when compared to women.¹

In an earlier study involving over 1000 Covid-19 patients, males accounted for 58% of cases.²  However, a review of over 72,000 patients reported by the Chinese CDC found nearly equivalent male to female ratio (~1:1).³ Among Covid-19 patients who have died, male to female ratio has frequently been found to be between 1.5-3.8:1, depending on the reporting country.¹  

In a case series from New York City, males accounted for 55% of Covid-19 patients not on invasive mechanical ventilation but 71% of those who required invasive mechanical ventilation.⁴ Chinese CDC reported case fatality rates of 2.8% for males and 1.7% for females.³ Higher case-fatality rates among males with 2 other coronavirus-related diseases, SARS and MERS, have also been reported.⁵

Potential explanations for more fatal outcomes among males with Covid-19 include more robust innate and humoral immune responses to infections among females.⁶ Immune suppressive activity of testosterone and potential immune enhancing effects of estrogens, such as increased expression of the anti-viral cytokine interferon (IFN)-gamma, have long been recognized.⁶ Life style differences between men and women such as higher prevalence of smoking in men are often mentioned as well.⁷ Interestingly, circulating ACE2, a receptor for SARS-CoV-2, has also been reported to be higher in men.⁸

Bonus pearl: Did you know that testosterone is associated with decreased production of pro-inflammatory cytokines such as IFN-gamma, TNF-alpha and may suppress immunoglobulin production?⁶

Liked this post? Download the app on your smart phone and sign up below to catch future pearls right into your inbox, all for free!

 References

1. Global Health 5050. Towards gender equality in global health. http://globalhealth5050.org/covid19/ , accessed April 27, 2020.
2. Guan WJ, Ni AY, Hu Y, et al. Clinical characteristics of coronavirus disease 2019 in China. N Engl J Med 2020;Feb 28, 2020. https://www.nejm.org/doi/full/10.1056/NEJMoa2002032
3. Chinese CDC. Vital surveillances: the epidemiological charcteristics of an outbreak of 2019 novel coronavirus diseases (COVID-19)-China, 2020; 2:113-22. http://weekly.chinacdc.cn/en/article/id/e53946e2-c6c4-41e9-9a9b-fea8db1a8f51
4. Goyal P, Choi JJ, Pinheiro LC, et al. Clinical characteristics of Covid-19 in New York City. N Engl J Med 2020, April 17. https://www.nejm.org/doi/full/10.1056/NEJMc2010419
5. Channappanavar R, Fett C, Mack M, et al. Sex-based differences in susceptibility to SARS-CoV infection. J Immunol 2017;198:4046-4053. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5450662/#!po=3.84615
6. Ysrraelit MC, Correale J. Impact of sex hormones on immune function and multiple sclerosis development. Immunology 2018;156:9-22. https://onlinelibrary.wiley.com/doi/epdf/10.1111/imm.13004
7. Wenham C, Smith J, Morgan R. COVID-19: the gendered impacts of the outbreak. Lancet 2020:395:846-7. https://www.ncbi.nlm.nih.gov/pubmed/32151325
8. Patel SK, Velkoska E, Burrell LM. Emerging markers in cardiovascular disease: Where does angiotensin-converting enzyme 2 fit in? Clin Exp Pharmacol Physiol 2013;40:551-9. https://www.ncbi.nlm.nih.gov/pubmed/23432153/

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Massachusetts General Hospital, Harvard Catalyst, Harvard University, its affiliate academic healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!