Atrial Fibrillation May Increase Risk of Dementia

Atrial fibrillation (AF) may increase the risk of dementia, according to a new study conducted in the Netherlands. The study looked at 20 years of follow-up data on over 6000 people, and found that younger participants with a longer duration of AF had the highest risk of dementia. The study was published online on September 21, 2015 in JAMA Neurology.¹

“In this population-based study, we found that individuals with AF had increased risk of dementia,” wrote first author Renee de Bruijn, MD, and colleagues at the Erasmus Medical Center in Rotterdam, the Netherlands. “This association was similar for Alzheimer disease and independent of stroke. The risk of dementia was highest in younger participants (<67 years), particularly if they had a longer period of AF.”

The study took place from July 1989 to February 2010, and included 6514 participants from the prospective population-based Rotterdam cohort study. At baseline, participants were free of dementia and 4.9% (315/6514) had AF.  Researchers defined incident dementia according to criteria from the Diagnostic and Statistical Manual of Mental Disorders (third edition, revised) and the National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer’s Disease and Related Disorders Association. They assessed AF using ECGs at baseline and at follow-up visits, and verified AF diagnoses by using two masked research physicians and checking with participants’ physicians. Results were censored for stroke, stratified by median age, and adjusted for age, sex, and cardiovascular risk factors.

Key results:

• Over 20 years of follow-up, 15.3% (994/6514) developed incident dementia
• Prevalent AF was linked to 33% increased risk of dementia (adjusted HR 1.33; 1.02-1.73)
• Younger participants had increased risk of incident dementia (<67 years: 1.81; 1.11-2.94; ≥67 years: 1.12, 0.85-1.46, p=0.02 for interaction)
• Younger patients with longer exposure to AF had increased risk for dementia (>12 years exposure: 3.30, 1.16-9.38, p=0.003 for trend)
• Older participants with longer exposure to AF did not have increased risk for dementia (0.25; 0.04-1.86, p=.94 for trend)
• Results were similar for Alzheimer disease
• The results did not significantly change after censoring for stroke

AF could increase the risk of dementia through various mechanisms, the authors explained. First, stroke is a serious complication of AF, and represents a well-known risk factor for dementia. Asymptomatic lacunar strokes, in particular, could explain these findings. Second, lower cardiac output in patients with AF could cause cerebral hypoperfusion, which can damage brain tissue. Finally, AF and dementia may have a shared etiology and overlapping risk factors like hypertension, diabetes and hypercholesterolemia.

The study did not include information about treatment after AF diagnosis, which could potentially affect the risk for dementia, the authors pointed out. Whether or not optimizing treatment for AF can improve dementia risk needs further study, they wrote.

“Our finding that AF is a risk factor for dementia has important clinical implications,” the authors concluded. ”Given that this arrhythmia has treatment options, the risk of dementia could potentially be reduced by optimal treatment of AF…More studies are needed to investigate whether optimal treatment of AF can prevent or delay the onset of dementia.”

References:

de Bruijn RF, Heeringa J, Wolters FJ, et al. Association between atrial fibrillation and demenia in the general population. JAMA Neurol. 2015 Sep 21:1-7. doi: 10.1001/jamaneurol.2015.2161. (abstract)