Framingham Heart Study data indicate that obesity may increase risk for atrial fibrillation, the most common arrhythmia, by 50 percent, according to an article in the November 24th issue of the Journal of the American Medical Association.

The prevalence of atrial fibrillation is expected to increase several-fold in the coming decades, according to background information in the article. Because the onset of atrial fibrillation is associated with considerable illness and a higher risk of death despite various therapies, identification of potentially modifiable risk factors is important. Although obesity has been associated with other heart problems, it has been unclear whether it is a risk factor for atrial fibrillation.

In the current study, Thomas J. Wang, MD, and colleagues examined long-term follow-up data from the Framingham Heart Study to determine if there were an association between body mass index and risk for atrial fibrillation. The study group included 5,282 participants (average age, 57 years; 2,898 women) without baseline arrhythmia.

The researchers examined risk for three categories of index: normal, defined as less than 25.0; overweight, 25.0 to less than 30.0; and obese, greater than 30.0. A 5’4” woman would have a body mass index of 30 if she weighed 174 pounds; a 6’00” man would have a body mass index of 30 if he weighed 221 pounds.

During an average follow-up of 13.7 years, 526 participants (234 women) developed the arrhythmia. Age-adjusted incidence rates for atrial fibrillation increased across the 3 index categories for men and women. In multivariable models adjusted for cardiovascular risk factors and interim myocardial infarction or heart failure, a 4 percent increase in arrhythmia risk per 1-unit increase in body mass index was observed in men. Obese men had a 52 percent increased risk for atrial fibrillation; obese women, 46 percent increased risk, in both cases compared with individuals with normal body mass index. The researchers found that the increased risk for atrial fibrillation may be mostly attributable to an associated dilation of the left atrium.

“… the implication of these results for the population burden of atrial fibrillation may be substantial, because obesity is highly prevalent and potentially modifiable. Thus, even a small decrease in the prevalence of obesity could lead to a large reduction in the incidence of atrial fibrillation,” the authors wrote.

“Because management of atrial fibrillation remains a difficult clinical challenge, the identification of potentially modifiable risk factors may have important public health implications. Although our study was observational, it raises the intriguing possibility that weight reduction may decrease the risk of atrial fibrillation,” the researchers wrote.

In an accompanying editorial, James Coromilas, MD, wrote that the study by Wang et al is important and timely, given the epidemic proportions of both obesity and atrial fibrillation.

“Obesity now needs to be considered a risk factor for the development of atrial fibrillation. Although the increased risk for the development of atrial fibrillation with increased body mass index is modest, the public health implications are substantive. Atrial fibrillation is responsible for a 3-fold to 5-fold increased risk of stroke and a 2-fold increased risk of mortality, and it is reaching epidemic proportions as the U.S. population ages.”

“Certainly, the adverse consequences of obesity are well documented and are behind major public health initiatives aimed at lifestyle modification, including exercise and diet. Now it seems that these life style modifications also may have an impact on the epidemic of atrial fibrillation and the morbidity and mortality associated with that condition,” concluded Coromilas.