['Many patients who develop atrial fibrillation (AF) will experience a worsening of their arrhythmia over time. The optimal time to proceed with catheter ablation during the disease course is unknown. Further, whether delays in treatment will negatively influence outcomes is unknown.', 'The purpose of this study was to examine the impact of delay in treatment after the first clinical diagnosis of AF on ablation-related outcomes.', 'A total of 4535 consecutive patients who underwent an AF ablation procedure that had long-term established care within an integrated health care system were evaluated. Recursive partitioning was used to determine categories associated with changes in risk from the time of first AF diagnosis to first AF ablation: 1: 30-180 (n = 1152), 2: 181-545 (n = 856), 3: 546-1825 (n = 1326), and 4: >1825 (n = 1201) days. Outcomes evaluated include 1-year AF recurrence, stroke, heart failure hospitalization, and death.', 'With increasing time to treatment, surprisingly patients were older (1: 63.7 ± 11.1, 2: 62.6 ± 11.8, 3: 66.4 ± 10.2, 4: 67.6 ± 9.7; P <.0001) and had more hypertension (1: 53.0%, 2: 59.0%, 3: 53.8%, 4: 39.0%; P <.0001). For each strata of time increase, there was a direct increase of 1-year AF recurrence (1: 19.4%, 2: 23.4%, 3: 24.9%, 4: 24.0%: P trend = .02). After adjustment, clinically significant differences in risk of recurrent AF were found when compared to the 30-180 day time category: 181-545: odds ratio (OR) = 1.23, P = .08; 546-1825: OR = 1.27, P = .02; and >1825: OR = 1.25, P = .05. No differences were observed for 1-year stroke among the groups. Death (1: 2.1%, 2: 3.9%, 3: 5.7%, 4: 4.4%: P trend = .001) and heart failure hospitalization (1: 2.6%, 2: 4.1%, 3: 5.4%, 4: 4.4%; P trend = .009) rates at 1 year were higher in the most delayed groups.'] Does increasing time between first diagnosis of atrial fibrillation and catheter ablation adversely affect long-term outcomes?