Mild Cognitive Impairment (MCI) in Patients With Atrial Fibrillation (AF), Trajectories of the Progression of MCI and Factors Associated With the Progression

Background: AF is mostly a disease of elderly. Up to 10% of people aged 80 years or older suffer from this arrhythmia and the rate is projected to triple in the next 20 years (1). Evidence is emerging that AF may increase the risk of all forms of dementia (2). Cerebral hypoperfusion and the risk of cerebrovascular micro- and macro-embolism are plausible explanations for the predisposition for cognitive decline in AF (1). Such insults may act alone or in concert with other neuropathological changes common in the brain of older individuals such as neuritic plaques or neurofibrillary tangles, in lowering cognitive reserves and accelerating the onset of dementia (3).

Prior studies on AF and dementia have yielded conflicting results.

An earlier study provided evidence supporting an association between AF and increased incidence of dementia in patients with stroke (4). In a prospective study conducted on participants of ONTARGET and TRANSCEND trials, it was revealed that cognitive and functional decline are important consequences of atrial fibrillation, even in the absence of overt stroke (5). Another independent study, observed similar results for risk of dementia in AF in participants with and without clinically recognized stroke during follow-up (3). Evidences from a previous research demonstrated not only a significant association of AF with all forms of dementia including Alzheimer's disease, but also higher mortality rate in patients with coexistent dementia and AF (2). On the contrary, some studies did not find any significant risk-association between AF and dementia (6-8).

These contradictory results compel the necessity for a prospective study on a large population to obtain a clear understanding of the association between AF and cognitive impairment. The potential association between the two conditions can have a very important clinical implication; if there were a causal relationship between AF and dementia then the different therapeutic strategies of AF may have differing influence on dementia risk (3). Thus, this knowledge would facilitate in personalizing treatment approaches for individuals with AF.

Anti-arrhythmic drugs are considered as the first line of therapy in AF and catheter ablation is widely-recognized as the best option in drug-refractory cases. Recent published data suggested that effective rhythm-control by catheter ablation reverses the risk of dementia in AF (9). However, it was an epidemiologic study from a health-care database where ICD codes were used to identify clinical dementia. Therefore, mischaracterization of the dementia subtypes was a major possibility in their study.