Atrial fibrillation (AF) is linked to an increased risk of dementia, even in people who have not suffered a stroke, a study* published in the European Heart Journal has found.
The study, the largest to investigate the association in an elderly population, also found that AF patients who took oral anticoagulants to prevent blood clots had a decreased risk of dementia.
The study looked at 262,611 people aged 60 or over in Korea, who were free of AF and dementia in 2004. Participants were followed up until the end of 2013, during which time 10,435 were diagnosed with AF.
In those who developed AF, 24.4% (2,522) developed dementia during the follow-up period compared to 14.4% (36,322) of the AF-free people.
Professor Boyoung Joung, professor of cardiology and internal medicine at Yonsei University College of Medicine, Seoul, Republic of Korea, who led the research, said: "We found that the people who developed atrial fibrillation had a 50% increased risk of developing dementia compared to those who did not develop the condition; this increased risk remained even after we removed those who suffered a stroke from our calculations. This means that, among the general population, an extra 1.4 people per 100 of the population would develop dementia if they were diagnosed with atrial fibrillation. The risk occurred in people aged younger and older than 70 years.
"We also found that atrial fibrillation increased the risk of Alzheimer's disease by 30% and more than doubled the risk of vascular dementia. However, among people who developed atrial fibrillation and who took oral anticoagulants, such as warfarin, or non-vitamin K anticoagulants, such as dabigatran, rivaroxaban, apixaban or edoxaban, the risk of subsequently developing dementia reduced by 40% compared to patients who did not take anticoagulants."
The researchers say this is the largest study to investigate the link between AF and dementia in people aged 60 and over who did not have AF and had not suffered a stroke at the time of inclusion in the study. The study also has the longest follow-up with an average of more than six years.
"With these large figures, we can be sure of our findings," said co-author, Professor Gregory Lip, professor of cardiovascular medicine at the University of Liverpool, UK, and an adjunct professor at Yonsei University College of Medicine.
"We also believe that our results can apply to other populations too, as they confirm similar findings of a link between atrial fibrillation and dementia in studies of people in Western and European countries.
"Our study suggests that the strong link between atrial fibrillation and dementia could be weakened if patients took oral anticoagulants. Therefore, doctors should think carefully and be readier to prescribe anticoagulants for atrial fibrillation patients to try to prevent dementia."
The researchers point out that their findings show only that there is an association between AF and dementia, and not that AF causes dementia. A possible mechanism for how AF might cause dementia is that AF patients often have alterations to the blood vessels in their brains, possibly from suffering mini strokes that are too small to show any outward symptoms, and this cerebrovascular damage could be implicated in the onset of dementia.
*Kim D, Yang P-S, Yu H T, et al. Risk of dementia in stroke-free patients diagnosed with atrial fibrillation: data from a population-based cohort. European Heart Journal, 18 June 2019, doi: 10.1093/eurheartj/ehz386