A groundbreaking study has found that post-menopausal women with lower levels of estrogen appear to be at higher risk of developing severe coronavirus.

The study, which was led by researchers at King's College in London found that higher levels of estrogen may have a protective effect against coronavirus.

Estrogen interacts with the immune system in various ways, including how many immune cells are produced and how they respond to infection. 

Using data from the COVID Symptom Study App, researchers examined the rate of predicted COVID-19 among post-menopausal women, pre-menopausal women taking the combined oral contraceptive pill and post-menopausal women taking hormone replacement therapy.

Results were taken from more than 500,000 women in the UK between May 7th and June 15th in 2020.

Researchers hypothesised that estrogen could serve as a protectant against COVID-19.

The study quickly found postmenopausal women had a higher rate of predicted COVID-19 than other studied women.

Women in the 45-50 age group were most likely to be at risk, with reported symptoms of anosmia (inability to smell), fever and a persistent cough.

Women who were using the combined oral contraceptive pill between 18-45 had a lower rate of predicted COVID-19 and corresponding reduced frequency of symptoms.

The rate of hospitalisation was also significantly lower in this group.

Hormone replacement theory in post menopausal women between 50-65 years was associated with an increased rate of predicted COVID-19 but not with hospitalisation. 

The researchers advised that hormone replacement therapy should be considered with caution due to the lack of information, route of administration as well as duration of treatment.

Joint lead author Dr Karla Lee, from King’s College London, said: “We hypothesised that pre-menopausal women with higher estrogen levels would have less severe COVID-19 when compared to women of the same age and BMI who had been through the menopause, and our findings supported this.

“Additionally, when we compared a younger group of women on the combined oral contraceptive pill (COCP) with a similar group not taking the COCP, we saw less severe COVID amongst those taking the COCP - suggesting hormones in the COCP may offer some protection against COVID-19.

“More research is certainly needed to further our knowledge.”