Race and stroke in an atrial fibrillation inception cohort: Findings from the Penn Atrial Fibrillation Free study.

BACKGROUND: Stroke may be the initial manifestation of atrial fibrillation (AF). Limited studies, however, have evaluated racial differences in stroke before the diagnosis of AF.

OBJECTIVE: We assessed racial differences in strokes that occurred before and after AF diagnosis in the Penn Atrial Fibrillation Free study.

METHODS: The Penn Atrial Fibrillation Free study consists of 56,835 patients from the University of Pennsylvania Health System who were free of AF at the index visit. We developed an inception cohort of 3507 patients with incident AF and without any remote history of stroke.

RESULTS: Among the AF inception cohort, there were 538 patients with ischemic strokes and 54 with hemorrhagic strokes. Nearly half (n = 254; 47%) of the ischemic strokes occurred within a 6-month period before the diagnosis of AF. Of these, the majority of strokes occurred either on the day of (n = 158) or within a 7-day period before (n = 30) the diagnosis of incident AF. The remaining 284 (53%) ischemic strokes occurred a median of 3.6 years (interquartile range 1.9-5.4 years) after AF diagnosis. Compared with whites, blacks had an independently higher risk of having an ischemic stroke either before (adjusted odds ratio 1.37; 95% confidence interval 1.03-1.81) or after (adjusted hazard ratio 1.67; 95% confidence interval 1.30-2.14) AF diagnosis.

CONCLUSION: In the population with incident AF, nearly half of the ischemic strokes occurred before the diagnosis of AF. Compared with whites, blacks had a higher risk of developing an ischemic stroke that persisted whether the stroke occurred in the period either before or after AF diagnosis.