Differences by Race/Ethnicity in the Prevalence of Clinically Detected and Monitor-Detected Atrial Fibrillation: MESA.

Background: African Americans are consistently found to have a lower prevalence of clinically detected atrial fibrillation (AF) than whites, despite a higher prevalence of major AF risk factors and higher risk of ischemic stroke. Long-term ambulatory ECG monitors provide the opportunity for unbiased AF detection. We determined differences by race/ethnicity in the prevalence of clinically detected AF and in the proportion with monitor-detected AF.
Methods: We conducted a cross-sectional analysis in the MESA (Multi-Ethnic Study of Atherosclerosis), a community-based cohort study that enrolled 6814 Americans free of clinically recognized cardiovascular disease in 2000 to 2002. At the 2016 to 2018 examination, 1556 individuals participated in an ancillary study involving ambulatory ECG monitoring and had follow-up for clinically detected AF since cohort entry.
Results: Among 1556 participants, 41% were white, 25% African American, 21% Hispanic, and 14% Chinese; 51% were women; and the mean age was 74 years. The prevalence of clinically detected AF after 14.4 years' follow-up was 11.3% in whites, 6.6% in African Americans, 7.8% in Hispanics, and 9.9% in Chinese and was significantly lower in African Americans than in whites, in both unadjusted and risk factor-adjusted analyses (adjusted rate difference, -6.6% [95% CI, -10.1% to -3.1%]; P <0.001). By contrast, in the same individuals, the proportion with monitor-detected AF using a 14-day ambulatory ECG monitor was similar in the 4 race/ethnic groups: 7.1%, 6.4%, 6.9%, and 5.2%, respectively (compared with whites, all P >0.5).
Conclusions: The prevalence of clinically detected AF was substantially lower in African American than in white participants, without or with adjustment for AF risk factors. However, unbiased AF detection by ambulatory monitoring in the same individuals revealed little difference in the proportion with AF by race/ethnicity. These findings provide support for the hypothesis of differential detection by race/ethnicity in the clinical recognition of AF, which may have important implications for stroke prevention.