• atrial fibrillation;
  • cardiac arrhythmia;
  • dementia;
  • Alzheimer disease;
  • epidemiology

OBJECTIVES: To determine whether atrial fibrillation (AF) is associated with risk of incident dementia or Alzheimer's disease (AD), beyond its effect on stroke.

DESIGN: Prospective cohort study.

SETTING: An integrated healthcare delivery system.

PARTICIPANTS: A population-based sample of 3,045 community-dwelling adults aged 65 and older without dementia or clinical stroke followed from 1994 to 2008.

MEASUREMENTS: AF was identified from health plan electronic data using International Classification of Diseases, Ninth Revision, codes from inpatient and outpatient encounters. Covariates came from self-report, study measures, and health plan data. Participants were screened every 2 years using the Cognitive Abilities Screening Instrument (range 0–100), with detailed neuropsychological and clinical assessment of those scoring less than 86. A multidisciplinary consensus committee determined diagnoses of all-cause dementia and possible or probable AD using standard research criteria.

RESULTS: AF was present in 132 (4.3%) participants at baseline and was diagnosed in 370 (12.2%) more over a mean of 6.8 years of follow-up; 572 participants (18.8%) developed dementia (449 with AD). The adjusted hazard ratio associated with AF was 1.38 (95% confidence interval (CI)=1.10–1.73) for all-cause dementia and 1.50 (95% CI=1.16–1.94) for possible or probable AD. Results were similar for participants with and without clinically recognized stroke during follow-up and in sensitivity analyses examining only probable AD.

CONCLUSION: AF is associated with higher risk of developing AD and dementia. Future studies should examine whether specific treatments, including optimal anticoagulation, can decrease this risk.