Abstract Body (Do not enter title and authors here): Background: Atrial fibrillation (AF) frequently co-occurs with chronic kidney disease (CKD), contributing to worse outcomes in patients with advanced renal impairment. However, national trends in mortality where CKD is the underlying cause and AF is a contributing cause remain poorly characterized. Identifying demographic and geographic disparities is critical to inform prevention and care coordination strategies.

Research Questions: What are the national trends in CKD-related mortality with comorbid AF as a contributing cause of death? How do these mortality patterns vary by sex, race, urbanization level, and geographic region?

Methods: We analyzed national mortality data from the CDC WONDER database from 1999 to 2020 for individuals aged >35 years. CKD (ICD-10: N18) was specified as the underlying cause of death, and AF (I48) as a contributing cause. Age-adjusted mortality rates (AAMRs) per 1,000,000 population were calculated. Temporal trends were evaluated using Joinpoint regression to estimate annual percent change (APC).

Results: A total of 18,231 deaths were identified with CKD as the underlying and AF as a contributing cause. AAMR more than doubled from 2.6 (95% CI, 2.3–2.8) in 1999 to 5.6 (95% CI, 5.3–6.0) in 2020 (APC = 8.1%; p<0.001). Cumulative AAMR was higher among males (6.3 [95% CI, 6.2–6.5]) than females (3.9 [95% CI, 3.8–4.0]). African Americans had the highest AAMR (6.5 [95% CI, 6.2–6.8]), followed by American Indians (4.7 [95% CI, 3.8–5.6]), Whites (4.7 [95% CI, 4.6–4.8]), and Asians (3.6 [95% CI, 3.3–3.9]). Mortality was lowest in large central metropolitan areas (4.5 [95% CI, 4.3–4.6]) and highest in small metropolitan areas (5.2 [95% CI, 5.0–5.4]). By Census region, the Midwest and South both had the highest AAMRs (5.0 [95% CI, 4.9–5.1]), followed by the Northeast (4.8 [95% CI, 4.6–5.0]) and West (4.4 [95% CI, 4.2–4.5]).

Conclusions: Mortality from CKD with comorbid AF has increased substantially over the past two decades, with disproportionate burden among males, African American and American Indian populations, residents of small metropolitan areas, and those living in the Midwest and South. These findings underscore the need for improved cardiovascular-renal care coordination and targeted health equity efforts in high-risk populations.