Racial and Urban-Rural Difference in the Frequency of Ischemic Stroke as Initial Manifestation of Atrial Fibrillation

Abstract

Objective: Atrial fibrillation (AF) may remain undiagnosed until the development of complications. We aimed to examine the epidemiology and racial/ethnic and rural/urban differences in the frequency of newly diagnosed AF manifesting as ischemic stroke in a nationally representative sample of Medicare beneficiaries. Methods: We used a 5% random sample of Medicare claims to identify patients newly diagnosed with AF in 2016. The primary dependent variable was stroke or transient ischemic attack (TIA) in the 7 days prior to the first AF diagnosis, i.e., stroke or TIA as the initial manifestation of AF. We constructed a multivariable logistic regression to quantify the association between race/ethnicity, urban/rural residence, and the primary dependent variable. Results: Among 39,409 patients newly diagnosed with AF (mean age 77 ± 10 years; 58% women; 7.2% Black, 87.8% White, 5.1% others), 2,819 (7.2%) had ischemic stroke or TIA in the 7 days prior to AF diagnosis. Black patients (adjusted OR [95% CI]: 1.21 [1.05, 1.40], vs. White) and urban residents (1.21 [1.08, 1.35], vs. rural) were at increased risk of stroke as the initial manifestation of AF. Racial differences were larger among patients aged ≥75 years, with adjusted ORs of 1.43 (1.19, 1.73) for Black vs. White patients, but non-significant for those aged <75 (P for interaction = 0.03). Conclusion: We observed significant and important differences in the risk of stroke as initial manifestation of AF between White and Black patients and between rural and urban residents. Our results suggest potential disparities in the identification AF across race/ethnicity groups and urban/rural areas.

Keywords: Medicare claims; atrial fibrillation; ischemic stroke; racial differences; urban/rural.

Figure 1

Age- and sex-adjusted proportion (%) of newly diagnosed atrial fibrillation patients with ischemic stroke as the first manifestation of atrial fibrillation by race and urban/rural residence. The x axis shows three race/ethnicity categories (White, Black and Others) and the y axis shows urban and rural areas. Each of the 6 boxes presents one race-area group (White-Urban, White-Rural, Black-Urban, Black-Rural, Others-Urban, and Others-Rural). The size of the box represents the sample size of each group. Dark blue indicates the lowest proportion of AF diagnosis manifesting as stroke, while dark red represents the highest proportion of AF diagnosis manifesting as stroke.

Figure 2

Interactions of race/ethnicity and urban/rural residence with age, sex, and area of deprivation index. ADI, Area of Deprivation Index. In addition to the listed factors, the model was also adjusted for CHA₂DS₂-VAS_c score, valvular disease, geographic region (Northeast, South, Midwest, and West), Medicaid enrollment, low income subsidy and end stage renal disease.