In the largest general population study ever conducted investigating the association between atrial fibrillation and dementia, Korean researchers have concluded there is a significant link between the common heart condition and the onset of neurodegenerative disease.

Several smaller studies in the past have concluded elderly persons suffering from atrial fibrillation, a form of irregular heartbeat, seem to be at significantly increased risk of developing dementia. Now a team of researchers has tracked the largest cohort of subjects yet in an effort to address methodological variations across these earlier studies and affirm this association.

The study followed 262,611 subjects for an average of six years. All subjects were over the age of 60 and free of both dementia and atrial fibrillation at the beginning of the research period. Over the research period around 10,000 subjects developed atrial fibrillation, of which a striking 24.4 percent subsequently developed dementia, compared to only 14.4 percent of the AF-free subjects developing dementia.

"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," explains Boyoung Joung, lead on the research team from Yonsei University College of Medicine. "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."

More specifically atrial fibrillation seemed to double a person's risk of developing vascular dementia, and increase Alzheimer's risk by 30 percent. Interestingly, those subjects taking oral anticoagulants to manage atrial fibrillation displayed reduced instances of dementia compared to those untreated atrial fibrillation subjects.

These results do mirror the data from prior smaller studies, in particular research from last year concluding, not only does atrial fibrillation increase a person's risk for dementia, but anticoagulant treatments can significantly mitigate that risk. These earlier, albeit smaller, studies were conducted in Western or European populations leading the Korean research team to confidently conclude the association applies broadly to subjects all over the world.

It is unclear exactly what this association between atrial fibrillation and dementia actually means, and the researchers are very specific in noting there is no evidence in these studies to suggest atrial fibrillation directly causes dementia. In fact, the researchers conclude in the study that, due to the suggestions dementia can take years to develop before symptoms become apparent, it is unlikely that atrial fibrillation actively contributes to the onset of neurodegenerative disease. If this were the case then atrial fibrillation would need to appear at much younger ages than it generally does. It could be more likely that similar underlying causes such as inflammation and oxidative stress can lead to both conditions.

At this stage the researchers simply suggest the data be used by doctors to more vigilantly treat cases of atrial fibrillation with the knowledge that the use of anticoagulants can be potentially broadly protective against the development of dementia. Further study is necessary, more specifically investigating which atrial fibrillation treatments better prevent dementia, and what mechanism may underpin this association.

The new research was published in the European Heart Journal.