Resting heart rate and incident atrial fibrillation in the elderly

Background: Alterations 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).

Methods: A 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.

Results: Over 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.

Conclusion: In 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.