Resting Heart Rate and Incident Atrial Fibrillation in the Elderly

BackgroundAlterations in autonomic tone and/or sinus node dysfunction are common with aging. We hypothesized that older persons with low or high heart rates represent a population with subclinical abnormalities who are more likely to develop atrial fibrillation (AF). MethodsA total of 5,226 participants aged 65 years or more (85% white; 42% male) with complete data from the Cardiovascular Health Study were used in this analysis. AF cases were identified during the yearly study electrocardiograms, participant history of a physician diagnosis, or by hospitalization data. Cox regression was used to compute hazard ratios (HR) and 95% confidence intervals (CI) for the association between resting heart rate and incident AF using clinically relevant categories (heart rate 60 beats/min, 60< heart rate beats/min 90 beats/min (reference), heart rate >90 beats/min) and as a continuous variable per 5 beats/min decrease. ResultsOver a median follow-up of 12.7 years, a total of 532 (10.2%) participants developed AF. In a multivariable Cox regression analysis, heart rates 60 beats/min (HR = 1.3, 95% CI = 1.1, 1.5), but not >90 beats/min (HR = 1.1, 95% CI = 0.52, 2.3), were associated with an increased risk of AF. Additionally, heart rate per 5 beats/min decrease was associated with an increased risk of AF (HR = 1.06, 95% CI = 1.01, 1.1). The results were consistent in subgroup analyses stratified by age, sex, race, and baseline cardiovascular disease. ConclusionIn the elderly, low heart rates are associated with an increased risk of AF. Potentially, underlying alterations in autonomic tone and/or subclinical sinus node dysfunction manifested as slow heart rate predispose to AF.