Atrial fibrillation and endurance exercise

COPENHAGEN, DENMARK. Several studies have concluded that men who regularly engage in vigorous exercise for extended periods of time are at increased risk of developing atrial fibrillation (AF), notably lone AF. A Danish research team has just completed a meta-analysis of 6 case-control studies comparing the prevalence of AF among athletes and gender- and age-matched controls.

The studies involved 655 athletes (regularly engaged in intense physical endurance sports) and 895 controls with an average (mean) age of 51 years (93% men). During a follow-up period ranging from 6 to 28 years, 147 cases of afib were observed among the athletes as compared to 116 cases among the controls. This corresponds to a prevalence of 23% among athletes as compared to 12.5% among controls, and a 5.29 times higher risk of developing afib among athletes. The researchers suggest that left atrial enlargement and increased vagal dominance are the most likely factors involved in predisposing athletes to the development of atrial fibrillation.

Abdulla, J and Nielsen, JR. Is the risk of atrial fibrillation higher in athletes than in the general population? Europace, Vol. 11, No. 9, 2009, pp. 1156-59

Editor’s comment: According to this recent meta-analysis, the prevalence of afib among controls was 12.5% versus 23% for athletes. A recent study involving almost 17,000 male American physicians concluded that about 10% of the participants had been diagnosed with afib with athletes, especially joggers, having increased risk. The officially accepted number for the prevalence (total number of cases of a disease in a given population at a specific time) of AF in American adults over the age of 20 years is about 1%. The total adult population (over the age of 20 years) in the USA (February 2009) is 221 million, which means that about 2.2 million people in the USA have atrial fibrillation. In addition, it is estimated that 4.3 million individuals in the European Union, and 8 million in China also suffer from AF. Yet here we have a study (the Copenhagen study) which found 263 cases of afib among 1550 participants, or a prevalence of 17%. The Physicians Health Study found that during 12 years of follow-up, 1661 men out of 16,921 developed AF, which means that the prevalence of AF among this group at 12 years follow-up was 9.8%. Something does not add up! Here we have two carefully controlled studies, one involving almost 17,000 physicians, concluding that the prevalence of AF is anywhere between 10 and 17%, and yet, the official figure is 1%. Am I missing something here, or is it more likely that in the USA in excess of 20 million people rather than 1 million actually have AF – obviously mostly undiagnosed?