Supplemental Material for: Population Mortality Involving Co-Reported Intracerebral Hemorrhage and Atrial Fibrillation or Flutter in the United States, 1999–2025: Trends, Demographic Disparities, and Forecasts to 2040

A retrospective analysis of death certificate data from the Centers for Disease Control and Prevention Wide-ranging Online Data for Epidemiologic Research (CDC WONDER) database was conducted, identifying deaths listing ICH (International Classification of Diseases, Tenth Revision [ICD-10] code I61) and AF or atrial flutter (ICD-10 code I48) in any cause-of-death field. Records were extracted on June 15, 2026; data for 1999 through 2024 came from final Multiple Cause of Death files and data for 2025 from the provisional file.

Age-adjusted mortality rates (AAMRs) were calculated per 100,000 total resident United States population and stratified by sex, race/ethnicity, census region, and urbanization. Joinpoint regression assessed temporal trends, and autoregressive integrated moving average (ARIMA) models projected rates through 2040. Results: From 1999 to 2025, 52,967 deaths with co-reported ICH and AF or atrial flutter were identified.

The overall age-adjusted mortality rate rose from 0.4 to 0.7 per 100,000 between 1999 and 2021 (annual percent change [APC] 1.53%, p=0.016) before stabilizing through 2025. AAMRs were higher among men than among women in every study year and increased across the study period among Black or African American decedents (APC 1.83%, p<0.000001). Rates were highest in the West, which recorded the highest regional rate in every study year, and in nonmetropolitan areas, which exceeded metropolitan rates in every year from 2012 onward; the Northeast was the only region with a significant decline after 2015.

Pooled state AAMRs ranged from 0.3 in Louisiana to 1.1 in Vermont, and 75.4% of deaths occurred in medical facilities. Conclusions: Population mortality involving co-reported ICH and AF or atrial flutter rose until 2021 and then stabilized, with differences by sex, race and ethnicity, and geography that persisted across the study period. Age-adjusted rates are projected to remain broadly stable through 2040.

These findings are descriptive. They do not establish that AF, anticoagulation, or anticoagulation-associated bleeding caused the hemorrhages recorded, and differences in hypertension control and anticoagulation management remain plausible but untested explanations that warrant direct study.</p>