Clinical and Economic Burden of Bleeding Events in Patients in the UK With Non-valvular Atrial Fibrillation Treated With Vitamin k Antagonists

Inclusion Criteria:- For the CPRD-HES cohort, patients will be included if they meet these criteria: * Have CPRD data linked to HES * Have an AF diagnosis (based on Read codes from CPRD or ICD-10 codes from HES) and have been treated with VKA during the study period -≥18 years old at index date * CPRD acceptability quality criteria are present. For the CPRD cohort, patients will be included if they meet the following criteria: * Have an Atrial Fibrillation (AF) diagnosis (based on Read codes from CPRD) and have been treated with VKAs during the study period * ≥18 years old at index date * CPRD acceptability quality criteria are present. Exclusion Criteria: For the two cohorts of interest, patients will be excluded if they meet the following criteria: * Fewer than 12 months of computerised data available prior to the index date (in order to provide a minimum amount of computerised history and to avoid issues associated with updating records when a patient joins a practice). The date of start of computerized records will be the latter of the patient's date of registration with the practice or the practice's Up-to-Standard (UTS) date (when the practice is deemed to be contributing data of adequate quality) * The practice is not UTS, or the patient is deemed "unacceptable" according to CPRD's quality criteria * There is evidence of valvular disease, repair, or replacement before (ie, up to 12 months prior to the index date) or during the study period * There are records of Novel anticoagulant (NOAC)