Meta-analysis links obesity to risk of atrial fibrillation

December 23, 2007 by Benjamin A. Olenchock M.D., Ph.D.

New York

One in four Americans is obese, meaning that their body mass index is over 30. Obesity is a risk factor for diabetes, coronary heart disease, some cancers, obstructive sleep apnea, and diastolic heart failure. A meta-analysis just published online in American Heart Journal reinforces that atrial fibrillation should be on this. Researchers from Beth Israel Medical Center in New York have gathered data from 16 published articles, including 123,249 patients. They found that in the general population, obesity was associated with increased risk of developing atrial fibrillation. In post-cardiac surgery patients, however, obesity was not associated with increased risk of atrial fibrillation.

The authors searched the Medline and Cochrane databases for all studies published between 1966 and May of 2007 containing the words obesity, overweight, body mass index, arrhythmia, and/or atrial fibrillation. Articles were included in the meta-analysis if they addressed the relationship between obesity and atrial fibrillation in either a population-based cohort or a post-operative cohort.

The 16 studies that fulfilled the inclusion criteria consisted of 5 population-based cohort studies (n=78,602 patients) and 11 post-operative studies (n=44,647 patients). The mean age was 56 years old, 48% of patients were women, and around one quarter of patients were obese. In the pooled analysis, obese patients were more likely to be hypertensive and diabetic, as expected. In the population-based cohort studies, obesity conferred a 49% increased risk of atrial fibrillation (OR 1.49, CI 1.36 to 1.64), while in the post-operative patients there was no increased risk of atrial fibrillation in obese patients (OR 1.08, CI 1.04 to 1.12). In the population-based studies, body mass index was correlated with degree of risk: overweight conferred a smaller increase in risk (OR 1.39, CI 1.05 to 1.83) than did obesity (OR 1.87, CI 1.43 to 2.44) compared with non-overweight individuals.

This meta-analysis demonstrated a large risk of atrial fibrillation associated with obesity. The exact mechanism of the increased risk is not known. The study did not adjust for covariates such as hypertension, diabetes, coronary artery disease, medication use, obstructive sleep apnea, or left-atrial diameter. The different risk associated with obesity post-cardiac surgery vs. in the general population is interesting. It is possible that the pathogenesis of atrial fibrillation is different in these two different patient populations, i.e. inflammation and altered hemodynamics might play a larger role post-operatively.

Nikolas Wanahita, Franz H. Messerli, Sripal Bangalore, Apoor S. Gami, Virend K. Somers, Jonathan S. Steinberg. Atrial fibrillation and obesity—results of a meta-analysis. Am Heart J, In Press, Available online 10 December 2007 DOI: 10.1016/j.ahj.2007.10.004