Abstract Background Non-vitamin K antagonist oral anticoagulants (NOACs) are increasingly preferred over vitamin K antagonists (VKAs) in atrial fibrillation (AF) management. However, differences in oral anticoagulant (OAC) prescribing according to patient's age, patient's sex and physician's specialty may be present. Purpose To investigate the incident and prevalent use of OACs, NOACs and VKAs, stratified by age, sex and prescriber, and factors associated with the choice of OAC on a full-population scale. Methods Using two Belgian nationwide healthcare databases, AF patients ≥45 years old with ≥1 OAC prescription claim between January 1st, 2013 and December 31st, 2019 were identified. OAC use was investigated per half-year with a repeated cross-sectional design, based on medication prescription claims on a day-to-day basis. Incident use was defined as the first OAC use during the study period in OAC-naïve AF patients, whereas prevalent OAC use was defined as at least 1 OAC dispensing during a specific half-year. Factors influencing NOAC versus VKA initiation were identified by multivariable logistic regression models. Results Among 448,661 included OAC-treated AF patients (260,184 prevalent NOAC and 188,477 prevalent VKA users), 297,818 were newly-treated (232,739 incident NOAC and 65,079 incident VKA users). The mean age of incident NOAC and VKA users was 76±10 and 71±12 years, and 48% and 47% were female, respectively. Incident OAC use ranged from 45–49 to 42–44 users/10,000 persons between 2013–2019, whereas prevalent OAC use increased from 337 to 435 users/10,000 persons. Incident and prevalent NOAC use exceeded VKA use since 2013 and 2015 respectively, and NOACs represented 92% of incident and 81% of prevalent OAC users in 2019. Apixaban was the most frequently used NOAC since 2016. NOACs were significantly more prescribed by cardiologists and to older patients, whereas VKAs were more initiated in patients with cardiovascular, renal and hepatic comorbidities. Prevalent OAC use increased less in women than men (+25% versus +33% between 2013–2019) and female subjects had a 5% significantly lower odds of NOAC versus VKA initiation than men after multivariable adjustment. Conclusions Prevalent anticoagulant use increased with 29% in Belgium between 2013 and 2019. However, potential (N)OAC underuse among female AF patients was observed. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Research Foundation Flanders (FWO)