Racial and ethnic disparities in the incidence of stroke and mortality in atrial fibrillation: a US nationwide study
Authors: Essien U , Tang J , Kim N , Hausmann L , Washington D , Mor M , Nguyen V , Gellad W , Fine M 
Published: October 2024

Abstract

Background
Atrial fibrillation (AF) is the most common arrhythmia globally and is associated with increased risks of cardiovascular mortality and ischemic stroke. Prior research has demonstrated racial/ethnic disparities in AF outcomes yet this work has been limited to small cohorts and did not adjust for anticoagulant therapy.

Purpose
We compared incidence of ischemic stroke and death by race/ethnicity for patients with AF in the Veterans Health Administration (VA), the largest integrated, low-cost, national healthcare system in the US.

Methods
In this retrospective cohort study we identified those with an outpatient diagnosis of AF and a confirmatory diagnosis ≦ 180 days of their index AF diagnosis enrolled in VA from January 1, 2014 to December 31, 2021, with follow-up for outcomes from the index AF diagnosis date until May 31, 2022. To create a cohort of incident AF cases, we excluded patients with an AF diagnosis or anticoagulant therapy in the 2 years prior to their index AF diagnosis. We also excluded patients with pre-existing valvular heart disease, prior stroke, receiving hospice care or who died within 180 days of index AF diagnosis. We categorized our independent variable as race (i.e., non-Hispanic American Indian / Alaska Native [AI/AN], Asian, Black, or White [reference group]), and ethnicity (i.e., Hispanic). Our primary outcomes were incidence of stroke or death at any point within the study follow-up period. To compare these outcomes by race/ethnicity we conducted a survival analysis, adjusting for anticoagulant use as a time-varying covariate along with sociodemographic factors (age, sex, region, area deprivation index), clinical factors (CHADS2VA2Sc stroke risk and HAS-BLED bleeding risk), and facility type.

Results
There were 187,080 patients in the final cohort including 0.5% AI/AN, 1% Asian, 9% Black, 4% Hispanic, 85% White; mean age was 73 years. Over a mean study follow-up period of 4.43 years, 65,375 (34.9%) patients died and 24,910 (13.3%) developed stroke. The adjusted hazard ratio [95% CI] for death was lower for Hispanic (0.84 [0.78, 0.91]) and Black (0.94 [0.91, 0.97]) patients than White patients. In contrast, the adjusted hazard ratio for stroke incidence was higher for Black (1.21 [1.16, 1.27]) and Hispanic (1.10 [1.03, 1.17]) patients than White patients. There was no difference observed between AI/AN or Asian and White patients in either outcome.

Conclusions
In a national cohort of patients with incident AF, we identified significantly higher rates of stroke in Black and Hispanic than White patients even controlling for myriad factors including anticoagulant use. Conversely, racial/ethnic disparities in mortality appear to be eliminated in VA, counter to prior data. Understanding the factors, beyond anticoagulation, driving disparities in stroke outcomes and identifying factors reducing mortality among minority groups is critical to improving overall AF care in the largest integrated US health system.Adjusted Hazard Ratios of Study Outcomes