Association between oral anticoagulants and COVID-19 related outcomes: two cohort studies

Wong, A. Y.; Tomlinson, L.; Brown, J. P.; Elson, W.; Walker, A. J.; Schultze, A. J.; Morton, C. E.; Evans, D.; Inglesby, P.; MacKenna, B.; Bhaskaran, K.; Rentsch, C. T.; Powell, E.; Williamson, E. T.; Croker, R.; Bacon, S.; Hulme, W.; Bates, C.; Curtis, H. J.; Mehrkar, A.; Cockburn, J.; McDonald, H. I.; Mathur, R. I.; Wing, K.; Forbes, H.; Eggo, R. M.; Evans, S.; Smeeth, L.; Goldacre, B.; Douglas, I. J.

Objectives: We investigated the role of routinely prescribed oral anticoagulants (OACs) in COVID-19 outcomes, comparing current OAC use versus non-use in Study 1; and warfarin versus direct oral anticoagulants (DOACs) in Study 2. Design: Two cohort studies, on behalf of NHS England. Setting: Primary care data and pseudonymously-linked SARS-CoV-2 antigen testing data, hospital admissions, and death records from England. Participants: Study 1: 70,464 people with atrial fibrillation (AF) and CHA2DS2-VASc score of 2. Study 2: 372,746 people with non-valvular AF. Main outcome measures: Time to test for SARS-CoV-2, testing positive for SARS-CoV-2, COVID-19 related hospital admission, COVID-19 deaths or non-COVID-19 deaths in Cox regression. Results: In Study 1, we included 52,416 current OAC users and 18,048 non-users. We observed no difference in risk of being tested for SARS-CoV-2 associated with current use (adjusted HR, 1.01, 95%CI, 0.96 to 1.05) versus non-use. We observed a lower risk of testing positive for SARS-CoV-2 (adjusted HR, 0.73, 95%CI, 0.60 to 0.90), and COVID-19 deaths (adjusted HR, 0.69, 95%CI, 0.49 to 0.97) associated with current use versus non-use. In Study 2, we included 92,339 warfarin users and 280,407 DOAC users. We observed a lower risk of COVID-19 deaths (adjusted HR, 0.79, 95%CI, 0.76 to 0.83) associated with warfarin versus DOACs. Similar associations were found for all other outcomes. Conclusions: Among people with AF and a CHA2DS2-VASc score of 2, those receiving OACs had a lower risk of receiving a positive COVID-19 test and severe COVID-19 outcomes than non-users; this might be explained by a causal effect of OACs in preventing severe COVID-19 outcomes or more cautious behaviours leading to reduced infection risk. There was no evidence of a higher risk of severe COVID-19 outcomes associated with warfarin versus DOACs in people with non-valvular AF regardless of CHA2DS2-VASc score.