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Atrial fibrillation (AF) has been linked with an increased risk for cognitive impairment and dementia in numerous studies over the past 2 decades. A recent meta-analysis of 21 studies evaluating the association between AF and cognitive impairment found that AF was associated with a higher risk for cognitive impairment and dementia, with or without a history of clinical stroke (relative risk [RR] 1.40; confidence interval [CI], 1.19-1.64)1
Other recent studies have yielded similar findings. A prospective study in hospitalized patients with chronic AF (n=260) found that 65% had mild cognitive impairment (95% CI, 59% -71%). Deficits were found across a range of cognitive domains, particularly executive function, visuospatial abilities, and short-term memory.2 A longitudinal analysis (n=5,150; mean follow-up, 7 years) found that patients who developed AF (10.7% of the study population) also developed cognitive impairment or dementia at earlier ages than people with no history of AF, even in the absence of clinical stroke.3
What accounts for the association between AF and cognitive impairment? “Our current understanding is that AF is certainly a risk factor for cognitive decline and dementia, but the biological mechanisms are uncertain,” said Evan L. Thacker, PhD, of the Department of Health Science at Brigham Young University.
“AF could hasten cognitive decline by at least 2 mechanisms,” said Dr. Thacker. “The first is cardioembolic infarcts, where blood clots arising in the heart could lodge in cerebral arteries, cutting off blood supply to portions of the brain tissue. The second is cerebral hypoperfusion, where suboptimal output of blood from the heart due to arrhythmia could result in poor circulation of blood to the brain.”
Further research is needed to determine the extent to which these potential mechanisms play an actual role in causing brain tissue damage and leading to cognitive decline, states Dr. Thacker. He points to a recent study showing that AF was associated with the presence of gross brain infarcts at autopsy, suggesting that cardioembolic infarction is an important mechanism linking AF with cognitive decline.4
“Alternatively, there could be health factors that cause both AF and cognitive decline that have escaped our notice,” said Dr. Thacker. “In our study we ruled out factors such as sex, race, education, smoking and alcohol use, diabetes, high blood pressure, and other heart diseases such as coronary heart disease and heart failure as potential explanations of the association of AF with cognitive decline.3 However, maybe other variables such as nutritional factors are important in causing both AF and cognitive decline,” he says.
Regardless of the mechanism or mechanisms involved, the link between AF and cognitive impairment has important clinical implications. “The association of AF with faster cognitive decline suggests that clinicians should be extra watchful for signs of cognitive decline in older patients with AF,” said Dr. Thacker.
Ball and colleagues suggest that even mild cognitive impairment may affect the ability of a patient with AF to adhere to a treatment plan, engage in adequate self-care, participate in medical decision making, or determine if they are at high risk for a serious event such as stroke.2 Such patients may require increased support from caregivers and healthcare providers, such as community pharmacy support or use of medicine reminder tools.2 Increased surveillance may be required to promote treatment adherence and adequate self-care.2
“Currently there is no specific treatment recommended to prevent or reduce cognitive decline in AF patients,” notes Dr. Thacker. However, a recent study by Thacker and colleagues showed that “older adults, including those with AF, who do better at maintaining their overall cardiovascular health enjoy a lower risk for cognitive impairment than older adults who are in poor cardiovascular health.” Based on this research, Thacker suggests that AF patients follow Life’s Simple 7™, a measure of cardiovascular health recently developed by the American Heart Association to monitor progress toward the association’s goal of improving the cardiovascular health of all Americans by 20% by the year 2020 while reducing deaths from cardiovascular diseases and stroke by 20%.5 Life’s Simple 7 addresses 4 modifiable lifestyle factors (smoking, diet, exercise, and body mass index) and 3 modifiable biologic factors (blood pressure, total cholesterol, and fasting glucose).6 Thus, says Dr. Thacker, the obvious steps for a patient with AF are to quit or avoid smoking, eat a healthy diet, be physically active, and maintain healthy body weight, blood pressure, blood sugar, and cholesterol levels.
What about the implications for treatment? “An important clinical question that has not been answered is whether treatment with anticoagulants in AF patients, for stroke prevention, would also prevent cognitive decline,” said Dr. Thacker. Indeed, a recent study, the first randomized, controlled study of its kind, found no evidence that anticoagulation confers any additional protection over aspirin against cognitive decline in patients with AF in the first 33 months of treatment, other than that provided by preventing clinical stroke.7 However, a benefit over a longer time period could not be ruled out.7
“Increasing evidence suggests a link between AF and cognitive decline in the absence of major stroke,” notes Nahal Mavaddat, PhD, of the Department of Public Health and Primary Care at the University of Cambridge in the UK, and lead author of the anticoagulation study. “However, the greatest risk of dementia-onset resulting from AF remains that of having a stroke. Therefore, stroke prevention must be the clinician’s most important concern with respect to cognitive decline in those with AF,” said Dr. Mavaddat. “Anticoagulation is often underused in patients with AF who have cognitive impairment, due to concerns regarding falls and poor compliance,” added Dr. Mavaddat. “However, this may leave such patients at risk of vascular events. Clinicians should not shy away from offering anticoagulation to appropriate at-risk patients, including those with milder degrees of dementia or cognitive impairment.”