Declining Incidence of Atrial Fibrillation-Associated Ischemic Stroke in Auckland, New Zealand (2012 versus 2021)

Abstract

BACKGROUND: Atrial fibrillation (AF) is a major cause of ischemic stroke (IS), and this risk can be substantially reduced with oral anticoagulants (OACs). Using the population-based ARCOS (Auckland Regional Community Stroke) study, we investigated the temporal trends in AF-associated IS. METHODS: We analyzed ARCOS IV (March 2011-February 2012) and ARCOS V (September 2020-August 2021). AF-associated IS incidence was compared using Poisson exact methods. Regional OAC dispensing trends were also evaluated. Propensity score-weighted logistic regression estimated the marginal association between cohort and AF-associated IS after standardizing for vascular risk factors. Interaction tests were performed for ethnicity, and sex-specific differences were assessed using heterogeneity testing. OAC-associated intracerebral hemorrhage rates were also examined. RESULTS: Among 1694 (ARCOS IV) and 1982 (ARCOS V) IS cases, the proportion of AF-associated IS declined from 32.4% to 21.5% (-10.8% [95% CI -13.7 to -8.0], P<0.0001). Crude AF-associated IS incidence fell from 49.0 to 32.7 per 100 000 population. A larger decline occurred in women (relative risk, 0.56) than men (relative risk, 0.76; p=0.02 for heterogeneity). Temporal reductions differed by ethnicity, with greater decline in the "Other" ethnicity categories, but not in Māori or Pacific peoples. During the same period, patients dispensed OACs increased from 1094 to 1928 per 100 000 (P<0.001). OAC-associated intracerebral hemorrhage increased from 2.1 to 3.6 per 100 000, equating to 11 IS cases prevented per excess intracerebral hemorrhage. CONCLUSION: AF-associated IS incidence declined in Auckland between 2012 and 2021, during a period of substantially increased community OAC use. Persistent ethnic inequities and sex-specific variation highlight the need for improved AF detection, risk stratification, and prevention strategies.