By Jared Bunch
Dementia is a disorder that is characterised by impairment of memory and an additional cognitive domain. It results in a decline in daily function and negatively impacts quality of life. In an aging population, dementia is an increasing problem in clinical practice as it primarily affects elderly patients. Alzheimer’s disease is the most common form of dementia in the elderly, and it accounts for 60-80% of cases.
In a parallel fashion, atrial fibrillation is the most common arrhythmia encountered, and similarly to dementia, its prevalence increases with age. Atrial fibrillation independently increases total mortality in patients with and without cardiovascular disease and is an important risk factor of stroke.
Intriguing data has emerged to suggest that atrial fibrillation is independently linked to memory impairment, cognitive decline, and general dementia. To understand if the prior data regarding atrial fibrillation reflected an aging-biased association only or a novel risk, we studied 37,025 patients with a mean age of 60.6 ± 17.9 years with no prior history of atrial fibrillation or dementia. In this population, 10,161 (27%) developed atrial fibrillation and 1535 (4.1%) dementia during the five-year follow-up.
Patients with dementia were older, and had higher rates of hypertension, coronary artery disease, renal failure, heart failure, and prior strokes. In an age-based, multivariable adjusted analysis, atrial fibrillation was independently associated with all dementia types, including Alzheimer’s disease. A finding in opposition of the potential of an aged-population bias, the highest risk of Alzheimer’s dementia was in the younger group (age<70 years, OR 2.30, p=0.001). The association of Alzheimer’s disease and atrial fibrillation actually became non-significant in older patients. Highlighting the need to understand this association between arrhythmia and cognition further to improve outcomes, we found that after dementia diagnosis, the presence or development of atrial fibrillation was associated with a marked increased risk of mortality (vascular dementia: HR=1.38, p=0.01, Alzheimer’s dementia: HR=1.45, p<0.0001) (This study was published in Heart Rhythm Journal, 2010; 7(4):433-7).
Many therapies have been studied as potential means to decrease dementia risk. These proposed therapies include antioxidant vitamins, B complex vitamins, omega fatty acids/fish oil, antihypertensive agents, cholinesterase inhibitors, hormone therapy, statins, nonsteroidal anti-inflammatory agents, and active lifestyles. The majority of studies have shown mixed or minimal benefits.
Lifestyle changes to increase activity and cholinesterase inhibitors have shown the most potential for favourably alternating cognitive decline. These findings largely suggest the need to consider novel therapies and approaches to reduce dementia risk.
We questioned if there exists an association between atrial fibrillation and dementia, if a relatively safe, but aggressive, rhythm control strategy to restore sinus rhythm would improve outcomes or minimise risk over time. Across multiple centres in the state of Utah, a total of 4,212 consecutive patients underwent atrial fibrillation ablation and had at least three years of follow-up.
We compared these patients (1:4) to 16,848 age/gender matched controls with atrial fibrillation (no ablation) and 16,848 age/gender matched controls without atrial fibrillation. Patients were enrolled from the large ongoing prospective Intermountain Heart Collaborative Study database and were followed for at least three years. Dementia occurred in 0.4% of the atrial fibrillation ablation patients compared to 1.9% of the atrial fibrillation no ablation patients and 0.7% of the no atrial fibrillation patients (p<0.0001). Further, Alzheimer’s dementia occurred in 0.2% of the atrial fibrillation ablation patients compared to 0.9% of the atrial fibrillation no ablation patients and 0.5% of the no atrial fibrillation patients (p<0.0001).
The most compelling data were not the comparison of the atrial fibrillation groups in which one group receives intervention, but the comparison between patients that received an atrial fibrillation ablation and those with no history of atrial fibrillation. The patients with atrial fibrillation that received an ablation had outcomes similar to those with no history of atrial fibrillation. Although the mechanisms behind the benefit after ablation are unknown, possibilities include sinus rhythm maintenance, clinical follow-up with careful management of anticoagulation and other cardiovascular risk factors, and selection bias.
Nonetheless, these data in aggregate suggest that there is an association between atrial fibrillation and dementia, including Alzheimer’s disease. These data also suggest that with durable and safe rhythm-control strategies we may be able to alter the long-term risk of cognitive decline in patients with atrial fibrillation and enhance their quality of life.
Jared Bunch is a cardiologist and electrophysiologist at the Intermountain Medical Centre, Utah, USA.