Clinical outcomes following atrial fibrillation diagnosis in routine practice: a nationwide cohort study in Sweden

Background Patients diagnosed with atrial fibrillation (AF) are at risk of clinically meaningful ischaemic and haemorrhagic events, and death. Contemporary data are essential to define residual risk in the real-world setting and to help identify the current unmet need. Purpose To describe the occurrence and cumulative incidence of clinical outcomes (ischaemic stroke [IS], all-cause mortality [ACM], major adverse cardiovascular/vascular events [MACE/MAVE], and major and minor bleeding), following AF diagnosis in routine practice in Sweden. Methods This nationwide cohort study used linked registers to identify adults newly diagnosed with AF in specialised inpatient and outpatient hospital care between 2013 and 2023, irrespective of previous oral anticoagulant therapy. Patients with prior AF, active cancer, chronic bleeding disorders, in-hospital death at index, or migration (prior 5 years) were excluded. The index date was the date of outpatient visit or discharge date of hospital admission for AF diagnosis; baseline characteristics were assessed for the preceding year. Clinical outcomes were defined as the first recorded occurrence after the index AF date, identified using registered ICD-10 codes for the outcomes of interest. Incidence rates (IR) of clinical outcomes per 1,000 person-years (PY) were estimated for years 1–3; cumulative incidence functions (CIF) accounted for death (or non-cardiovascular death for MACE) as a competing risk. Prespecified stratifications included age and sex. Patients were followed up to 12 years until outcome, death, emigration, or 31 December 2024. Results The analyses included 323,109 patients (mean age: 74 years; 44% female). In the year prior to AF diagnosis, patients had a mean CHA2DS2-VA score of 2.9, 85% had hypertension or were receiving hypertensive treatment, 15% had diabetes, and 28% received oral anticoagulants. Median follow-up was 48.7 months. ACM was the most frequent clinical outcome post-AF diagnosis (year 1 IR: 127.1 PY), followed by minor bleeding, major bleeding, and IS (64.1, 49.1, and 28.9 PY, respectively). Year 1 IR was 111.2 PY for MAVE and 100.1 PY for MACE. For all outcomes, a decreasing trend for IR was observed over time. Age-and sex-stratified analyses showed higher cumulative incidence of ACM and IS at 1, 3, and 10 years post-index among patients aged ≥75 years (CIF ACM: 18%, 37%, 79% [Panel 1a]; IS: 3%, 5%, 10% [Panel 2a]) and female patients compared with male patients (ACM: 14%, 27%, 61% vs 10%, 21%, 51% [Panel 1b]; IS: 3%, 5%, 9% vs 2%, 4%, 8% [Panel 2b]). Conclusions In this large nationwide cohort study in Sweden, patients with newly diagnosed AF experienced persistent risks of clinical outcomes. These findings highlight a substantial residual risk following AF diagnosis in routine practice and an ongoing clinical need for treatment approaches capable of reducing this risk, particularly among female patients.