CHADS₂ score and risk of new-onset atrial fibrillation: A nationwide cohort study in Taiwan

Background: The components of CHADS2 score were reported to be important risk factors for the development of atrial fibrillation (AF). The goal of the current study was to investigate whether the CHADS2 score was a useful scheme in predicting new-onset AF. Furthermore, we aimed to use the CHADS2 scoring system to estimate the individual risk in developing AF for patients with different comorbidities. Methods: From January 1, 2000 to December 31, 2001, a total of 702,502 patients older than 18 years old and who had no history of cardiac arrhythmias were identified from the "National Health Insurance Research Database" released by the Taiwan National Health Research Institutes. The CHADS2 score was calculated for every patient. Finally, 628,807 (score 0), 47,039 (score 1), 15,655 (score 2), 6843 (score 3), 3315 (score 4), 790 (score 5) and 53 (score 6) patients were studied and followed for the occurrences of AF. Results: During a follow-up of 9.0±2.2 years, there were 9187 (1.3%) patients experiencing new-onset AF. The incidence of AFwas 1.5 per 1000 patient-years. The incidence increased from0.8 per 1000 patient-years for patients with a CHADS2 score of 0 to 34.6 per 1000 patient-years for those with a CHADS2 score of 6. After an adjustment for the gender and comorbidities, the hazard ratio (95% confidence interval) of each increment of the CHADS2 score in predicting AF was 2.342 (2.309-2.375; p<0.001). Conclusions: The CHADS2 score, consisting of an age >75 and several clinical risk factors was useful in risk estimation and stratification of new-onset AF.