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Trial Lecture – time and place
See Trial Lecture.
Adjudication committee
- First opponent: Assistant Professor Emma Svennberg, Karolinska Institutet, Sweden
- Second opponent: Assistant Professor Konsta Teppo, University of Turku, Finland
- Third member and chair of the evaluation committee: Professor II Helge Skulstad, University of Oslo
Chair of the Defence
Professor II Kristine Sahlberg, University of Oslo
Principal Supervisor
Trygve Berge, Vestre Viken HF
Summary
Atrial fibrillation (AF) is a major risk factor for ischemic stroke. Oral anticoagulation (OAC) reduces stroke risk, but at the cost of an increased bleeding risk. The net benefit is uncertain in patients at intermediate risk of stroke (CHA₂DS₂-VA score of 1). Stroke risk increases over time, but the optimal reassessment interval is unknown.
Using nationwide Norwegian registry data, the thesis aimed to quantify stroke and bleeding risk in intermediate-risk patients with AF with and without OAC, and compare the risk to individuals without AF with the same CHA₂DS₂-VA score. We also aimed to explore changes in CHA₂DS₂-VA score and estimate optimal time interval for reassessment after incident AF, and to examine temporal trends in stroke incidence in Norway.
In intermediate-risk patients with AF, OAC use was associated with a 53% lower risk of ischemic stroke, and the combined outcome of ischemic stroke, major bleeding and mortality favoured OAC (HR 0.57). Non-anticoagulated AF patients had 2.5-times higher risk of ischemic stroke compared to individuals without AF with the same risk profile.
In a cohort of patients with incident AF and a CHA₂DS₂-VA score of 0 or 1, 50% developed new risk factors within a median follow-up of 1.7 years. Significant age differences in risk progression highlight the need for individualized reassessment intervals, and we suggest a shorter interval of 6 months for patients aged ≥55 years and 1 year for those <55 years, and routine reassessment at age 65 and 75 years.
Stroke incidence decreased in Norway from 2001 to 2021, but this favourable decline did not include AF-related strokes. In fact, AF-related ischemic strokes increased in younger age groups, while AF-related intracerebral haemorrhage increased in the oldest patients, driven by OAC use.
The findings underscore the need for more individualized stroke prevention in AF, including timely risk reassessment, appropriate OAC use, and attention to bleeding risk in elderly patients.
Additional information
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