The Grapevine

Irregular Heart Rhythm Could Indicate Higher Dementia Risk

A new study on atrial fibrillation (AF) prevalence in dementia patients confirms older research linking the heart condition with higher susceptibility to dementia. The significance of the investigation is the scale of the analysis because previous studies were mixed and not conclusive. Larger longitudinal studies with a follow-up over a long period of time have not been done before.

More importantly, the beneficial role that oral anticoagulants (blood thinners) play in reducing the incidence of dementia by treating AF first was confirmed by researchers at Yonsei University College of Medicine in Seoul, Republic of Korea.

The Centers for Disease Control and Prevention (CDC) estimates that 2.7 to 6.1 million Americans are afflicted with AF and the numbers are only bound to increase with the aging population growing. It is the most common type of arrhythmia, a condition characterized by irregular heart beat, and affects approximately 2 percent of people younger than 65 and 9 percent of people above 65 years of age. Since forty million people worldwide suffer from dementia, examining the association of the condition with AF could potentially bring that number down, given that dementia still remains an untreatable condition. 

A study published in the European Heart Journal on June 18 documented the relationship between the two diseases. Specifically, incidences where AF precludes dementia were studied from data available in the Korea National Health Insurance Service Senior Cohort. The NHIS-Senior database has information pertaining to medical records, socioeconomic backgrounds and insurance on 5.1 million or 10 percent of the elderly population in South Korea aged above 60 in 2002.  

Cardiovascular disease New research confirms that patients with atrial fibrillation have a higher risk of developing dementia. Photo courtesy of Shutterstock

Between the years 2005 and 2012, as many as 262,611 people without dementia and stroke younger than 60 years old were enrolled. At the time, 10,435 patients patients with AF were assessed.  Those who had dementia before enrolling in the study were excluded from patients of other heart diseases and stroke, for the researchers were keen on documenting the risk of dementia in newly diagnosed AF cases for accuracy.  

Over the course of many years, from the patients with AF, nearly one fourth of them or 24.4 percent were diagnosed with dementia. Comparatively, 14.4 percent without AF developed dementia. Lead author Boyoung Joung said that people with atrial fibrillation on oral anticoagulant medication (warfarin, apixaban or dabigatran) had 40 percent lower risk of dementia when compared to patients who didn’t take blood thinners.

Previous research restricted the age of subjects to below 67 years of age, since the reasoning was that the longer the person has AF, the risk of dementia was higher because the disease develops most commonly in old people. An elderly cohort suggested that subjects older than 70 were equally susceptible to dementia.

There are many pathways that could cause dementia in people with AF. The two common types of dementia are Alzheimer's disease and Vascular Dementia (VD). The latter occurs in people with high risk of stroke, hence the researchers were categorical that AF also increased risk of dementia in people without stroke.

The limitations of the study are that the researchers were not aware of the medication taken by the participants to treat atrial fibrillation, since the subjects could be taking other medications apart from blood thinners. Therefore, the researchers were not sure if treatment affected the risk of dementia differently.

Paroxysmal atrial fibrillation occurs intermittently and disappears on its own within seven days. The study does not differentiate between quick or persistent atrial fibrillation, hence a few cases may have been excluded. Additionally, they were unaware of the blood pressure of the participants.