Chronic atrial fibrillation: Incidence, prevalence, and prediction of stroke using the Congestive heart failure, Hypertension, Age >75, Diabetes mellitus, and prior Stroke or transient ischemic attack (CHADS2) risk stratification scheme.

BACKGROUND: The aim of the study is to estimate the incidence and prevalence of chronic AF (cAF) in the United Kingdom and test the accuracy of the CHADS2 score for stroke prediction.
METHODS: The General Practice Research Database was used to identify patients aged 40+ years diagnosed with cAF and control patients. Harrell's C-statistic was used to test possible improvements in CHADS2.
RESULTS: The study population included 51,807 cAF patients. The incidence of cAF increased by age and was higher in men than women. The prevalence of cAF has increased over time. The excess 5-year risk for stroke in cAF patients correlated well with CHADS2 as follows: score 0, 1.9% (95% CI 1.6-2.1); 1, 3.0% (95% CI 2.7-3.3); 2, 4.7% (95% CI 4.3-5.1); 3, 7.2% (95% CI 6.6-7.9); 4, 10.5% (95% CI 9.4-11.5); 5, 13.9% (95% CI 12.2-15.5); and 6, 15.8% (95% CI 13.5-18.1). Adding sex, the extension of age categories and reweighing of established risk factors improved CHADS2 accuracy (C-statistic 0.68-0.72). Applying the reclassification resulted in a substantial number of patients changing stroke risk category.
CONCLUSION: Atrial fibrillation is a prevalent and growing problem, which significantly increases the risk of ischemic stroke. The CHADS2 score is a good predictor of the stroke risk but could be improved.