BOSTON, MASSACHUSETTS. Although the average age at diagnosis of lone atrial fibrillation (LAF) is about 47 years, by far the majority of AF patients are diagnosed at age 65 years or older. Studies have shown that the 10-year risk of a 65-year-old developing AF is about 20%. Researchers at Harvard Medical School now report that older people can substantially reduce this risk by engaging in light to moderate exercise on a regular basis.

Their study included 5446 adults aged 65 years or older who enrolled in the Cardiovascular Health Study in 1989-1990. The participants were examined at baseline and every year for the 12-year follow-up period. About half the participants had hypertension, about 20% had coronary heart disease, 25% had chronic pulmonary disease, and about 18% had diabetes when entering the study. During the follow-up, 1061 new cases of AF were diagnosed either during the annual ECG recordings or from hospital discharge records. Thus, about 1 in 5 participants developed AF during the follow-up. At the start of the study and at the 3rd and 7th annual visits usual leisure-time activity (kcal per week), usual exercise intensity, and usual walking habits were assessed.

The researchers observed that study participants who walked 60 or more city blocks (3-4 miles) a week had half the risk of developing AF than did those who walked 4 blocks or less a week. Walking pace was also important with people walking at speeds greater than 3 mph (4.8 km/hr) having half the risk of those walking at speeds less than 2 mph (3.2 km/hr). Regular engagement in leisure-time activities was also protective with participants expending in excess of 1840 kcal/week having a 36% lower risk of developing AF than those expending less than 35 kcal/week.

The relationship between exercise intensity and AF risk was U-shaped, that is, a low level of exercise and high intensity exercise were significantly less protective than was a moderate level of exercise which reduced AF risk by about 28% (compared to no exercise at all). NOTE: All the above risk reduction estimates have been adjusted for age, gender, race, education level, smoking status, alcohol use, use of beta-blockers, and the presence of coronary heart disease, chronic pulmonary disease and diabetes.

The researchers noted that having suffered a heart attack or having congestive heart failure increased the risk of developing AF by almost 5 times. They also point out that physical activity lowers blood pressure and resting heart rate, and improves glucose control, cholesterol levels, and mental well-being. They conclude that moderate physical exercise, especially walking, is associated with a significantly lower AF incidence in older adults.

Mozaffarian, D, et al. Physical activity and incidence of atrial fibrillation in older adults. Circulation, Vol. 118, August 19, 2008, pp. 800-07

Editor�s comment: It is likely that the study underestimated the prevalence of paroxysmal AF, particularly the asymptomatic kind since ECGs were only obtained once a year or upon hospital admission. Nevertheless, walking half a mile a day at a brisk pace would seem to be a small price to pay to reduce the risk of non-lone atrial fibrillation by about 50%.