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Less Dementia and Stroke in Low-Risk AF Patients Taking Oral Anticoagulation
Study Questions:
Do patients with atrial fibrillation (AF) who use oral anticoagulation (OAC) despite a low risk of stroke have a lower risk of dementia, ischemic stroke, or intracranial hemorrhage than similar patients who do not use OAC?
Methods:
The authors used a national registry in Sweden to identify patients diagnosed with AF between 2006 and 2014. Patients with a CHA2DS2-VASc score of >1, not counting female sex, were excluded. The authors also excluded patients with a history of intracerebral hemorrhage (ICH) or dementia. The study endpoints were a new diagnosis of dementia, ischemic stroke, or ICH, as well as composite of these three outcomes. Pharmacy records determined the type of OAC prescribed. Propensity scores were used to compare patients using OAC with those who were not.
Results:
After applying exclusion criteria, there were 91,254 patients diagnosed with AF: 39,160 using OAC at baseline and 52,094 who were not using OAC at baseline. After propensity score matching, there were two cohorts of patients (n = 23,746 in each group) using, and not using OAC. The mean follow-up was just under 5 years.
The use of OAC was associated with a reduced risk of dementia (sub-hazard ratio [sHR], 0.62; 95% confidence interval [CI], 0.48-0.81). The benefit of OAC in reducing the diagnosis of dementia was seen in patients with a CHA2DS2-VASc score of 1, as younger patients were rarely diagnosed with dementia. In the study, there was no association between OAC and the risk of ischemic stroke or ICH. OAC use was protective when the composite endpoint of dementia, ischemic stroke, or ICH was evaluated (hazard ratio [HR], 0.88; 95% confidence interval [CI], 0.77-1.00). When the composite endpoint was stratified by age, the benefit of OAC was restricted to patients >65 years old. There was no difference in the composite endpoint between using a non–vitamin K oral anticoagulant (NOAC) compared with those using a vitamin K antagonist (HR, 0.47; 95% CI, 0.18-1.22), although only 7.5% of patients were using a NOAC at baseline.
Conclusions:
For patients with AF at low risk of stroke, OAC use may reduce the risk of dementia.
Perspective:
Vascular risk factors, including AF, are associated with an increased risk of developing dementia. Prior studies have shown that in patients with AF, OAC use is associated with a decreased risk of developing dementia. It is thought that OAC reduces the risk of embolization from AF and the embolization contributes to the dementia risk. Patients with AF who are at low risk of stroke, as determined by the CHA2DS2-VASc score, are generally not treated with OAC. As a randomized controlled trial of OAC in this population is challenging, the use of a registry, as done by the authors, is a good way to address the study question.
The findings that OAC use reduced the risk of dementia as well as the composite endpoint of dementia, ischemic stroke, and ICH in patients >65 years has the potential to simplify the decision to anticoagulate patients with AF. If all patients with AF >65 years benefit from OAC use, then evaluation of additional risk factors may not be necessary when making decisions about starting anticoagulation. While these results are intriguing, caution is warranted before incorporating them into clinical practice, as this is not a randomized study and results may be due to confounding factors. Additionally, adherence to OAC is not captured in the data and could contribute to bias.
Clinical Topics: Anticoagulation Management, Arrhythmias and Clinical EP, Anticoagulation Management and Atrial Fibrillation, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Sleep Apnea
Keywords: Anticoagulants, Arrhythmias, Cardiac, Atrial Fibrillation, Dementia, Brain Ischemia, Cerebral Hemorrhage, Dementia, Intracranial Hemorrhages, Risk Factors, Stroke, Vascular Diseases, Vitamin K
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