Physical Activity, Resting Heart Rate, and Atrial Fibrillation
What is the relationship between exercise, resting heart rate, and atrial fibrillation (AF)?
The subjects of this study were 20,484 adults (mean age 38 years) who participated in a survey in Norway in 1986-1987. Physical activity was assessed with a detailed questionnaire and resting heart rate (RHR) was measured. The individuals then were followed for a mean of 20 years. Individuals who developed AF were identified on the basis of a hospital-based diagnosis.
AF was diagnosed in 750 individuals during follow-up. The AF incidence was 2.62/1,000 person-years in men and 1.07/1,000 person-years in women. In a multivariate analysis, moderate activity (walking, cycling, or other exercise for ≥4 hours/week) was independently associated with a 19% lower risk of AF compared to low activity. The risk of AF associated with high activity or vigorous activity (intense training or competition several times/week) did not differ significantly from the risk in low-activity individuals. There was a weak but significant inverse relationship between physical activity and RHR. The risk of AF decreased by 8% for every 10 bpm increase in RHR.
The authors concluded that moderate exercise reduces the risk of AF and a low RHR increases the risk of AF.
The finding that a low RHR heightens the risk of AF suggests that the increase in baseline vagal tone associated with vigorous exercise may play a role in attenuating or eliminating the protective effects of moderate exercise on the development of AF.
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