Estrogen-modulating treatment among mid-life women and COVID-19 morbidity and mortality: a multiregister nationwide matched cohort study in Sweden

Abstract

Background: It has been repeatedly shown that men infected by SARS-CoV-2 face a twofold higher likelihood of dying, being hospitalized or admitted to the intensive care unit compared to women, despite taking into account relevant confounders. It has been hypothesized that these discrepancies are related to sex steroid hormone differences with estrogens being negatively correlated with disease severity. The objective of this study was therefore to evaluate COVID-19-related mortality and morbidity among peri- and postmenopausal women in relation to estrogen-containing menopause hormonal treatments (MHT). Methods: This is a national register-based matched cohort study performed in Sweden between January 1 to December 31, 2020. Study participants comprised women over the age of 53 years residing in Sweden. Exposure was defined as prescriptions of local estrogens, systemic estrogens with and without progestogens, progestogens alone, or tibolone. MHT users were then compared with a matched cohort of non-users. The primary outcome consisted of COVID-19 mortality, whereas the secondary outcomes included inpatient hospitalizations/outpatient visits and confirmed SARS-CoV-2 infection. Multivariable adjusted Cox regression-derived hazard ratios (HRs) were calculated. Results: Use of systemic estrogens alone is associated with increased COVID-19 mortality among older women (aHR 4.73, 1.22 to 18.32), but the association is no longer significant when discontinuation of estrogen use is accounted for. An increased risk for COVID-19 infection is further observed for women using combined systemic estrogens and progestogens (aHR 1.06, 1.00 to 1.13) or tibolone (aHR 1.21, 1.01 to 1.45). Use of local estrogens is associated with an increased risk for COVID-19-related death (aHR 2.02,1.45 to 2.81) as well as for all secondary outcomes. Conclusions: Systemic or local use of estrogens does not decrease COVID-19 morbidity and mortality to premenopausal background levels. Excess risk for COVID-19 morbidity and mortality was noted among older women and those discontinuing systemic estrogens. Higher risk for death was also noted among women using local estrogens, for which non-causal mechanisms such as confounding by comorbidity or frailty seem to be the most plausible underlying explanations. Trial registration details: Not applicable.