Atrial fibrillation poses people at higher risk of dementia
Association of Atrial Fibrillation With Cognitive Decline and Dementia Over 20 Years: The ARIC‐NCS (Atherosclerosis Risk in Communities Neurocognitive Study)Chen LY, Norby FL, Gottesman RF, et al. - J Am Heart Assoc. 2018;7:e007301.
Introduction and Methods
Atrial fibrillation (AF) has been associated with an increased risk of stroke, heart failure, death. Evidence is inconsistent about a potential relationship with cognitive decline and dementia, due to limited follow-up . This analysis of the ARIC study evaluated the associations of incident AF with cognitive change and dementia onset among black and white adults was, in a community-based cohort over 20 years.
ARIC is a predominantly biracial community-based, prospective, cohort study, including 15,792 men and women, aged 45-64 years at baseline or visit 1 (1987-1989) . Baseline for the present analysis was visit 2 (1990-1992), at which the first cognitive data were collected. Of the 14,348 participants who attended visit 2, those not identified as black or white, those with prevalent AF, those with prevalent dementia or with race-gender specific lowest 5th percentile cognitive test scores, those missing or with uninterpretable ECGs, those missing cognitive scores, and those missing other covariates of interest were excluded, leaving a study sample of 12,515 participants.
The assessment of cognitive function was done with 3 neuropsychological tests:
- the Delayed Word Recall Test (DWRT), which evaluates verbal learning and short-term memory 
- the Digit Symbol Substitution Test (DSST) of the Wechsler Adult Intelligence Scale–Revised, which evaluates executive function and processing speed 
- the Word Fluency Test (WFT), which evaluates executive function and expressive language 
The diagnosis of dementia was done during visit 5 (2011-2013), by an in-person assessment, using an algorithm as defined in the National Institute on Aging–Alzheimer’s Association work groups  and the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition . Z scores standardized to visit 2 were calculated for each test, to be able to compare them, and the three Z-scores were then used to calculate the composite global cognitive Z score. Methods to account for attrition from the cohort during follow-up were used, which is important in quantifying the long-term relationship of AF to cognitive decline and dementia.
- After accounting for CV risk factors and conditions, the average decline over 20 years in the composite global cognitive Z score was 0.123 (95%CI: 0.027–0.230) greater in participants with AF than in those without AF.
- After further adjustment for prevalent and incident stroke, the association was slightly attenuated but remained significant: the average decline over 20 years in global cognitive Z score was 0.742 in participants without AF and 0.857 in those with AF (difference: -0.115; 95%CI: -0.215 to -0.014; a 16% greater decline among the latter).
- After accounting for attrition, AF was associated with significantly greater decline in the scores of all tests, and after further adjustment for prevalent and incident stroke, AF remained significantly associated with greater decline in global and DSST Z scores.
- Compared with participants without AF (N=10,504, incidence rate per 1000 person-years [PY]: 4.48), those with AF (N=2011, incidence per 1000 PY: 21.21) had a significant 23% higher risk of dementia (HR: 1.23; 95%CI: 1.04-1.45; P=0.02), after adjustment for age, gender, race, education, occupation, apolipoprotein E, smoking, body mass index, systolic and diastolic blood pressure, use of hypertensive medication, diabetes, prevalent coronary heart disease or heart failure, as well as prevalent and incident stroke.
Incident AF is associated with both greater cognitive decline and increased risk of dementia, independent of clinical ischemic stroke. These results raise the question how cognitive decline and dementia may be delayed or prevented in AF patients. Research is warranted to identify appropriate treatment.