The “Double” Paradox of Atrial Fibrillation in Black Individuals

Atrial fibrillation (AF) affects more than 33 million people worldwide and is associated with increased risks for stroke, heart failure, and death.1,2 One explanation for the increasing incidence and prevalence of arrhythmia may relate, in part, to the aging of the population in Western countries.However, the recent identification of novel risk factors for AF such as race, obstructive sleep apnea, metabolic syndrome, and obesity may also play a role in the growing AF epidemic.3 Despite a greater burden of well-established risk factors, black individuals are less prone to develop AF than white individuals of European ancestry for reasons that are not completely clear.Possible etiologies of this AF paradox include the differential impact of ethnic-specific risk factors and an underlying genetic basis for the reduced incidence and prevalence of AF among black individuals.4 We examined the race-and sex-specific influences of demographic, lifestyle, anthropometric, and medical factors on the development of AF in more than 8000 participants in the Southern Community Cohort Study.5 Although the prevalence of AF was significantly lower among black individuals (11%) than white individuals (15%), the patterns of AF risk were similar between the 2 racial groups.However, associations with well-established risk factors such as hypertension, diabetes, and stroke were somewhat stronger among black individuals.Of note, this study 5 showed that traditional risk factors for AF were responsible for 58% of the burden of AF among black individuals, in contrast to 44% in white individuals, which is consistent with other studies demonstrating that only 50% of people with AF in the population can be explained by wellestablished risk factors.Although this study 5 included a large cohort of black individuals and white individuals of similar socioeconomic status, extensive baseline data, and systematic and unbiased follow-up data on evaluations of participants for AF, novel risk factors for AF were not examined.Nonetheless, the findings of our study emphasize that approximately 50% of the burden of AF among black individuals was not explained by well-established risk factors implicating other etiologies for the AF paradox.Another possible explanation for the AF paradox among black individuals may relate to an underlying genetic basis, with Marcus et al 6 showing that the proportion of European ancestry in African American individuals was associated with an increased risk for AF in individuals enrolled in the Cardiovascular Health Study and the Atherosclerosis Risk in Communities Study.