Abstract Body (Do not enter title and authors here): Introduction
Atrial fibrillation (AF) is a growing public health concern in the United States, particularly among older adults. AF complications like stroke and heart failure result in increased healthcare utilization. We sought to assess how future costs of atrial fibrillation are projected to change across care types and U.S. states to identify disparities and demographic shifts that may influence care delivery and system preparedness.

Methods
Population, health encounters, and direct health spending were estimated from 2000-2019 across all 50 U.S. states and the District of Columbia and then forecast using ensemble models through 2050 in 2019 dollars stratified by six types of care (TOC) including inpatient, ambulatory, emergency, retail pharmaceutical, nursing facility, and home health. Estimates were modelled using public and private administrative health facility and pharmacy data. ICD codes identified AF-related encounters and therapies and were used to adjust for comorbidity.

Results
Total spending for AF was projected to increase from $30 billion (B) in 2019 to $72.9B in 2050. Retail pharmaceutical spending represented the majority of spending on AF in 2050 at $29.4B, an annualized percentage change (APC) of 7.6% from 2019-2050. Spending on other TOC were ambulatory ($21.3B; APC 5.1%), inpatient ($11.9B; APC 1.8%), nursing facility ($5.8B; APC 2.9%), home health ($2.4B; APC 5%) and emergency ($2.1B; APC 5.8%). In 2050, AF spending per capita was highest for retail pharmaceuticals ($90 per person), followed by ambulatory care ($58.7), inpatient care ($32.8), nursing facility ($15.9), home health ($6.5), and emergency department ($5.9). Projected per capita state AF spending in 2050 was highest in Connecticut ($358.5), New York ($309.3) and Rhode Island ($279.1). Utah ($127.3), New Mexico ($139.5), and Alaska ($150.2) were projected to spend the least. Among these states, ambulatory spending was projected to narrowly outpace pharmaceutical spending only in Alaska.

Conclusion
Atrial fibrillation spending in the U.S. is forecasted to more than double by 2050, driven primarily by projected increases in pharmaceutical spending. Per capita AF expenditures vary widely by state, with the Northeast region projected to bear the highest financial burden. Given that AF is both preventable and highly treatable, this variation may reflect disparities in underdetection and access to care across states.