Increased direct oral anticoagulant use and event rates in non-valvular atrial fibrillation: a nationwide retrospective registry study in Sweden

RATIONALE: The use of direct oral anticoagulants (DOACs) as stroke prophylaxis in patients with non-valvular atrial fibrillation (NVAF) has increased steadily since the introduction in 2011. In Sweden today, more patients are treated with DOACs than with warfarin. However, it is not shown that an increased proportion of DOAC prescriptions correlates to lower event rates of stroke and systemic embolism. OBJECTIVES: This study aims to investigate whether the increased prescription of DOACs in Sweden correlates with lower event rates for all-cause stroke, systemic embolism and bleeding complications, using real-life data for the whole NVAF population. DESIGN: Nationwide retrospective register study. SETTING: Data were obtained from the Swedish National Patient Registry, covering patients aged 18 years or older with NVAF, between 1 January 2014, and 31 December 2017. Exposure to oral anticoagulants was determined based on pharmaceutical data, calculating treatment duration by the number of pills dispensed and the prescribed daily usage rate. Baseline characteristics and endpoints were collected from hospital administrative registers using International Classification of Diseases, 10th edition (ICD-10) codes. PARTICIPANTS: All patients with NVAF were identified using ICD-10 codes during the study period. Entry criteria included having a first recorded atrial fibrillation diagnosis after 1 January 2014 or being previously diagnosed with atrial fibrillation before 2014 but still receiving care after this date. OUTCOME MEASURES: The outcomes were event rates (per 100 person-years) of ischaemic stroke, systemic embolism, all-cause stroke, major bleeding and intracranial bleeding (including haemorrhagic stroke). Event rates were calculated and compared across the study period using Cox proportional hazard models. RESULTS: In the total NVAF population, the proportional decrease in event rates (per 100 treatment years) in 2017 compared with 2014 was ischaemic stroke 24% (1.70-1.30), all-cause mortality 4% (9.40-9.00), all-cause stroke 24% (2.10-1.60) and all-cause stroke and systemic embolism 23% (2.20-1.70). During the same time, the proportion of major bleeding and intracranial bleeding rates, including haemorrhagic stroke, also decreased: 5% (2.00-1.90), 6% (0.68-0.64) and 17% (0.30-0.25), respectively. DOACs use increased from 4.1% to 28.3% in the total population and from 22.7% to 60.9% in newly diagnosed patients. CONCLUSIONS: In the initial years following the introduction when DOAC uptake in the population was high, an increasing proportion of Swedish NVAF patients receiving DOACs was accompanied by lower event rates of all-cause stroke and systemic embolism, ischaemic stroke and all-cause mortality, intracranial bleeding and major bleeding, highlighting the improved risk-benefit balance of DOACs in stroke prophylaxis.