Physical Activity and the Risk of Atrial Fibrillation
Abstract & Commentary
By John P. DiMarco, MD, PhD, Professor of Medicine, Division of Cardiology, University of Virginia, Charlottesville. Dr. DiMarco is a consultant for Novartis, and does research for Medtronic and Guidant.
Source: Mozaffarian D, et al. Physical activity and incidence of atrial fibrillation in older adults. The Cardiovascular Health Study. Circulation. 2008;118:800-807.
The relationship between physical activity and atrial fibrillation has been controversial. Lone atrial fibrillation is relatively common in young, competitive athletes, and it is uncertain whether routine physical activity is protective or harmful in elderly populations where atrial fibrillation is more common. In this paper, Mozaffarian and his colleagues analyzed data from the Cardiovascular Health Study, which included data about new onset atrial fibrillation and physical activity in a well described population.
The Cardiovascular Health Study enrolled 5,201 men and women over age 65 in 1989-1990. An additional 687 black participants were added to the study in 1992. Baseline information included standardized physical examination, diagnostic testing, laboratory evaluation, and questionnaires that included data on health status, medical history, lifestyle habits, and cardiovascular risk factors. For this report, patients with coexisting diseases that might limit physical activity (eg, claudication, angina, visual handicap, or COPD) were excluded. Leisure time physical activity was assessed at baseline and at the third and seventh annual visits by a modified Minnesota leisure time activity questionnaire. The incidence of new onset atrial fibrillation was identified through annual resting 12 lead ECGs, interim six-month telephone contacts, and hospitalization records of participants.
Data from 5,446 patients were available for analysis in this study. At baseline, the average age was 73 years; 58% were women and 17% were non-white. The group was divided into quintiles by the amount of leisure time activity and quartiles by the intensity of leisure time activity. Greater leisure time activity was associated with slightly younger age, male gender, white race, greater education, greater alcohol use, and fewer cardiovascular risk factors. Greater physical activity was also associated with lower blood pressure, lower heart rates, improved serum lipids, and lower C-reactive protein levels. During 12 years of follow-up, there were 1,061 new cases of atrial fibrillation documented, for an overall incidence rate of 22.4 cases per 1,000 person years. Increased leisure activity and exercise intensity were both associated with a lower risk for AF; however, there was a nonlinear relationship between exercise intensity and AF incidence. Patients with moderate intensity exercise had a 28% lower risk of AF, but individuals with the highest intensity exercise did not have a significantly lower risk than those with no regular exercise. Adjustment for comorbid factors and for coexistent myocardial infarction and congestive heart failure modified the protective effects of exercise slightly, but did not affect the overall pattern. In a multivariate analysis, the proportion of all new cases of atrial fibrillation attributable to lack of physical activity was 26%.
Mozaffarian et al conclude that moderate physical activity may meaningfully reduce the risk of AF, and suggest that lifestyle modification should be further evaluated as a potential preventive measure to reduce AF incidence.
Commentary
It has been previously noted that atrial fibrillation is common among high-intensity, especially endurance-competitive athletes. Atrial fibrillation may be vagally mediated and associated with nocturnal bradycardia. However, in others, it may be catecholamine mediated and occur frequently with exercise in those patients who frequently subject themselves to peak levels of adrenergic stimulation. The data from the Cardiovascular Health Study, in contrast, suggests that routine exercise is protective against atrial fibrillation. It is interesting that they found the highest intensity group was not protected from new onset AF, whereas moderate levels and increased durations of activity were protective. They suggest that high levels of adrenergic stimulation during exercise may have some negative effects on atrial fibrillation in the elderly, as well as in young athletes.
The findings from the study support the concept that regular exercise should be part of a routine wellness program in subjects able to exercise. Participation in high-intensity sports, however, is not the goal, and the slight increase in risk for AF associated with competitive sports should be considered by older patients who wish to participate in them.
The relationship between physical activity and atrial fibrillation has been controversial. Lone atrial fibrillation is relatively common in young, competitive athletes, and it is uncertain whether routine physical activity is protective or harmful in elderly populations where atrial fibrillation is more common.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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