Increased risk of first-ever stroke in younger patients with atrial fibrillation not recommended for antithrombotic therapy by current guidelines: a population-based study in an East Asian cohort of 22 million people.

OBJECTIVE: To assess the risk of first-ever ischemic stroke in younger patients with atrial fibrillation (AF) who have none of the CHA2DS2-VASc (congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, previous stroke/transient ischemic attack, vascular disease, age 65-74 years, sex category [female sex]) risk factors (excluding female sex) by using the National Health Insurance research database in Taiwan.

PATIENTS AND METHODS: From 22,842,778 insured people, we identified 24,612 hospitalized patients with newly diagnosed AF between January 1, 2002, and December 31, 2004, as the AF group and randomly selected 98,448 age- and sex-matched persons without AF as the non-AF group. Both groups were followed up until December 31, 2010, to estimate ischemic stroke incidences in relation to other stroke risk factors.

RESULTS: During a follow-up period of 89,468 person-years, the stroke rate was higher in patients with AF than in those without AF (5.79 per 100 person-years vs 2.25 per 100 person-years). The higher prevalence of CHA2DS2-VASc comorbidities (heart failure, hypertension, diabetes, coronary artery disease, and peripheral artery disease) in patients with AF further increased the stroke risk. In 790 patients with AF aged 30 to 55 years who had none of the CHA2DS2-VASc comorbidities at baseline and retained a "low risk," that is, those with a CHA2DS2-VASc score of 0 in men and 1 in women during follow-up, the stroke rate remained considerably higher than that in their non-AF counterparts (1.00 per 100 person-years vs 0.25 per 100 person-years), with a sex-adjusted hazard ratio of 4.09 (95% CI, 2.97-5.62).

CONCLUSION: This study finds an increased risk of stroke in younger patients with AF who are not recommended for prevention of thromboembolism by current guidelines. Better stroke risk stratification tools are needed to prioritize younger patients with AF for thromboprophylactic therapy in this population.