Atrial Fibrillation Linked to Increased Risk of Dementia

November 6, 2018

Researchers found a link between atrial fibrillation and an increased risk of dementia and concluded that anticoagulants could help decrease that risk.

Mozhu Ding, MSc, PhD Candidate

According to a recent study published in Neurology, atrial fibrillation (AF) is associated with a faster global cognitive decline and an increased risk of dementia in elder adults, however, those taking anticoagulants were less likely to develop dementia than those who did not.

Researchers examined the associations of AF with dementia, dementia subtypes and cognitive decline in individuals 60 years and older, and explored the cognitive benefit of antithrombotic treatment in those with AF.

“Both the incidence of AF and dementia increases with age. The clinical implications of our findings are that, in addition to the well-known risk of stroke, the increased risk of vascular dementia warrants a more proactive approach in continuously identifying AF in elderly populations,” co-authors Mozhu Ding, MSc, PhD Candidate, and Petter Ljungman, MD, PhD, told NeurologyLive. “In addition, we emphasize the needs to improve the clinical management of AF patients, since many AF patients are under-treated, and our research underscores the strong protective effect of anticoagulant treatment in AF patients against dementia. While there is currently no cure for dementia, we estimated that 54% of all dementia cases could be prevented if all AF patients were treated with anticoagulant therapy. However, our results do not suggest any beneficial effect of antiplatelet therapy in preventing dementia.”

Data were derived from the Swedish National Study on Aging and Care in Kungsholmen (SNAC-K) study of individuals 60 years and older living at home or in institutions in Kungsholmen. The study population consisted of random samples from 11 age cohorts and included 2685 participants who were followed for an average of 6 years as part of a larger study. The population had a mean age of 73.1 years and 62.9% were women.

Participants younger than 78 were examined at baseline and then once after 6 years, and participants older than 78 were examined and interviewed and once every 3 years. At baseline, all participants were dementia free, but 243 participants (9.1%) were identified as having AF.

AF was determined through EKG and physician’s diagnosis at baseline and follow-up. Participants with AF at baseline were considered to have prevalent AF, while those who developed AF during follow-up prior to diagnosis of dementia or death were considered to have incident AF. At each examination, global cognitive function was assessed using the Mini-Mental State Examination (MMSE) and dementia was clinically diagnosed according to Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) (DSM-IV) criteria following a validated 3-step procedure.

During the 9-year follow-up period from 2001—2004 to 2010–2013, 279 (11.4%) of the 2442 AF-free participants developed incident AF; a total of 399 (14.9%) incident dementia cases were detected, which included 166 (6.2%) with Alzheimer disease and 68 (2.5%) with either vascular dementia or mixed dementia. As a time-varying variable, AF was significantly associated with a faster annual MMSE decline (β coefficient = −0.24, 95% confidence interval [CI]: −0.31 to −0.16) and an increased hazard ratio (HR) of all-cause dementia (HR = 1.40, 95% CI: 1.11–1.77) and vascular and mixed dementia (HR = 1.88, 95% CI: 1.09–3.23), but was not significantly associated with the risk of Alzheimer disease (HR = 1.33, 95% CI: 0.92–1.94). Participants with AF had a faster rate of decline in cognition than those without AF and were 40% more likely to develop dementia. Of the 2163 individuals who did have AF, 278 developed dementia (10%), and of the 522 with AF, 121 developed dementia (23%).

“We demonstrate the relevance of AF as risk factor for both cognitive decline and dementia in persons older than 60 years, and this connection, although predominantly of vascular etiology, is independent of ischemic stroke and many other clinical diseases,” said Ding and Ljungman. “This highlights the importance of continuous vigilance in monitoring for AF, especially since we also observed more than 100% additional incident AF cases in the follow-up. More importantly, we show evidence that use of anticoagulant drugs could potentially decrease the risk of dementia among older AF patients.”

Anticoagulants use was linked to a 60% reduced risk of dementia (HR = 0.4; 95% CI, 0.18—0.92), while antiplatelet drugs was not significantly associated with an increased risk (HR = 1.84, 95% CI: 0.99–3.42). Of the 342 individuals not taking anticoagulants, 76 developed dementia (22%) and of the 128 participants taking anticoagulants, 14 developed dementia (11%).

“Both the strong risk for dementia and stroke in elderly patients with AF and the simultaneous strong preventive effect of anticoagulant treatment in these patients presents a strong impetus to identify AF in elderly and offer them anticoagulant treatment,” Ding and Ljungman noted when asked about the additional questions this research opens up. “So the questions are how do we more aggressively detect AF given that AF can be asymptomatic or present with relatively mild symptoms, making diagnosis elusive? Is there a stronger case for AF screening in elderly, e.g. with 2-lead thumb ECGs coupled with a biomarker? Among those with AF, what factors contribute to the abstinence from anticoagulant treatment and should we reconsider this in the wake of the double menace of stroke and dementia risk in AF patients? In addition, we are also interested in which specific mechanisms are underlying the observed association between atrial fibrillation, cognitive decline, and dementia.”

Researchers reported that limitations included not being able to distinguish subtypes of AF, and that there could have been asymptomatic AF cases that were missed.

Future studies are needed to clarify the possible cognitive benefits of anticoagulant drugs in patients with AF.

“There is increasing evidence that AF, although a heart condition, is a crucial predictor of cerebrovascular health and dementia and should be aggressively pursued by multiple disciplines including cardiologists, general practitioners, gerontologists, neurologists and other clinicians who encounter elderly patients, especially since we can offer effective and straightforward protection from stroke and dementia,” Ding and Ljungman conclude. “We are planning a neuroimaging study, which aims to investigate to what extent “silent" brain lesions and atrophy detected on magnetic resonance images mediate the association of atrial fibrillation with cognitive decline and dementia.”

REFERENCE

Ding M, Fratiglioni L, Johnell K, et al. Atrial fibrillation, antithrombotic treatment, and cognitive aging. Neurology. 2018;91:1—9.

doi

:10.1212/WNL.0000000000006456.