Association of Left Atrial Structure and Function with Incident Atrial Fibrillation in Black and White Adults: the ARIC Study

Background: Black individuals have a lower incidence of atrial fibrillation (AF) than White individuals despite a higher burden of many traditional cardiovascular risk factors. Differences in left atrial (LA) structure and function by race could partly explain the observed pattern of AF risk. Methods: This analysis included 4,576 (978 Black and 3,598 White) participants from the Atherosclerosis Risk in Communities (ARIC) study, followed between 2011 and 2021. The association of selected echocardiographic measures of LA structure and function with AF incidence was evaluated with race-specific Cox proportional hazards models with adjustment for sociodemographic and clinical covariates. Additional analyses assessed whether LA measures attenuated the association between race and incident AF. Results: The analysis included 778 AF cases (113 in Black and 665 in White participants, mean age 75 years). Larger LA size and worse LA function were associated with higher AF risk in both Black and White individuals, with most associations of similar magnitude in both groups, except for a slightly stronger association of LA reservoir strain in Black than White participants (Black: hazard ratio (HR) 0.89, 95% CI 0.86-0.92 per 1% increase; White: HR 0.94, 95% CI 0.92-0.95, p for interaction = 0.01). In the overall sample, White participants showed higher AF risk compared to Black participants (HR 1.59, 95% CI 1.24-2.03). Adjustment for most individual LA measures did not attenuate the association between race and AF risk. Conclusion: Larger LA size and worse LA function were associated with incident AF in both Black and White ARIC participants. However, these measures did not explain the lower AF incidence observed among Black participants. LA remodeling appears to be an important predictor of AF risk, but it is not the primary explanation for the Black-White AF paradox.