- It's been proven that men are more like to contract and die from severe Covid-19
- A preprint study claims that oestrogen could be protecting women from the virus
- A comparison between pre- and post-menopausal women indicates that low oestrogen makes women a bigger target
One of the stranger phenomena of Covid-19 is that men have been proven to be at higher risk of severe Covid-19 than women – and the answer might lie in female hormones.
It is known that oestrogen, the female sex hormone, allows for stronger immune responses to viral infections, including coronaviruses.
But, does this also apply Covid-19?
Answer lies in menopause
A new preprint study from King's College London, that still needs to be peer-reviewed, aimed to find this out by comparing menopausal women to younger women with higher levels of oestrogen. Oestrogen levels decrease when women reach menopause, which generally happens between the ages of 40 and 60.
The data was collected over five-and-a-half weeks from hundreds of thousands of UK women using the country's Covid Symptom Tracker Application.
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Contraceptives also key
The study also looked at women on contraceptives and post-menopausal women undergoing hormone replacement therapy.
The study did not include smokers, those with high body mass index and those using oestrogen therapy for gender transitioning.
"Age is a key risk factor for Covid-19. Age sensitivity analyses were performed to match the mean and median ages of cases and controls for each of the three exposure variables," explained the authors.
The researchers found that post-menopausal women had a higher rate of predicted Covid-19, with a higher frequency of symptoms that included a hoarse voice, skipped meals, muscle pains, and fever.
Those taking contraceptives were less likely to contract Covid-19, and if they did, had far fewer symptoms and were less likely to be hospitalised.
"The association between [contraceptive pill] use and tested Covid-19 as an outcome was not significant, but showed a consistent negative direction of association in the 25–30 and 35–40 age groups."
When they compared post-menopausal women on hormone therapy with those who weren't, they did not find any statistical difference related to predicted Covid-19 infection.
However, the study cautions that they didn't have enough data on women undergoing hormone replacement therapy and added that there's a stigma attached to hormone replacement therapy in the UK.
The researchers also posit that oestrogen levels might be why pregnant women are only half as likely to present with severe Covid-19 compared to the rest of the population. (Women's oestrogen levels skyrocket during pregnancy.)
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How age affects the results
"The associations between menopausal status and Covid-19 positivity and symptom severity may in part be related to biological ageing, rather than a reduction in oestrogen specifically, although the [contraceptive pill] use results suggest that this is unlikely.
"This was supported by a protective effect seen among pre-menopausal women taking the [contraceptive pill] but was not seen for post-menopausal women taking [hormone replacement therapy]."
They also controlled for ageing-related confounders by using a small twin study test for correlation between ageing and Covid-19 symptoms.
More work to be done
It is important to note that the data was self-reported, and the use of a phone app might not be representative of those who can't afford phones or the elderly who are less likely to use smartphones frequently.
"Further work focused on gender with hormone profiling in both pre-clinical and clinical settings, as well as on biological ageing, is needed to uncover novel features of the host immune response to SARS-CoV-2 and ultimately result in more equitable health outcomes," the writers conclude.
Currently, there are studies in New York and California underway where oestrogen steroid hormones and progesterone – another female sex hormone – are administered to adult men and older women to determine whether this could be a way to replicate the sex hormone's potential protective effect against the deadly virus.
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