Trends in Incidence of Atrial Fibrillation–Related Stroke: The Norwegian AFNOR Study

BACKGROUND: The increasing prevalence of atrial fibrillation (AF), along with changes in cardiovascular risk factors, AF detection and oral anticoagulant use, may have altered the epidemiology of AF-related stroke. However, population-based data on long-term trends remain limited. METHODS: Using mandatory nationwide registry data from the Atrial Fibrillation in Norway (AFNOR) study (2001-2021), we identified incident stroke cases defined as first hospitalization or death due to stroke in individuals aged ≥15 years. Age-standardized incidence rates were calculated using direct standardization. Sex- and age-adjusted incidence rate ratios (IRR) were estimated using negative binomial regression. RESULTS: Among 227 575 incident strokes, 66 795 (29.4%) were AF-related, and increased from 22% to 31% during 2001-2021, with 69% of all AF-related ischemic strokes occurring in non-anticoagulated individuals. Incidence rate of AF-related ischemic strokes remained stable overall (67.8 per 100 000 person-years in 2001 to 68.4 in 2021; IRR=1.01; 95% CI, 1.00-1.03) but increased among individuals aged 15 to 64 years. Non-AF ischemic strokes declined from 204.4 to 130.8 (IRR=0.98; 95% CI, 0.97-0.99). Incidence of AF-related intracerebral hemorrhage in individuals aged ≥75 years increased, driven by anticoagulated patients. Incidence of non-AF intracerebral hemorrhage decreased (IRR=0.98; 95% CI, 0.97-0.99). CONCLUSIONS: The favorable decline in ischemic stroke incidence from 2001 to 2021 did not include AF-related strokes. AF-related ischemic strokes increased in younger age groups, whereas AF-related intracerebral hemorrhage increased in the oldest age groups driven by anticoagulated patients. These findings underscore the need for improved strategies for AF detection and stroke prevention, particularly in younger populations, and greater attention towards management of bleeding risk among older, anticoagulated individuals.