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April 27, 2005

Obesity and the Risk of New-Onset Atrial Fibrillation

JAMA. 2005;293(16):1974-1975. doi:10.1001/jama.293.16.1974-c

To the Editor: Dr Wang and colleagues1 conclude that obesity is an important risk factor for AF and that this excess risk appears to be mediated by left atrial enlargement. We are concerned about 3 potential limitations of this study.

First, AF was diagnosed by electrocardiograms obtained either from hospital or physician charts or from routine Framingham clinical examinations. However, obese participants were approximately 2 to 3 times more likely to be receiving antihypertensive medications and approximately 2 to 5 times more likely to have diabetes than were normal-weight participants. As a result, obese participants are likely to have had more hospital and physician visits—and hence more chances of having their AF diagnosed. This is especially relevant to new-onset AF, in which spontaneous conversion to sinus rhythm occurs in almost two thirds of patients2,3 and in which up to 90% of episodes are not even recognized by the patients.4 The authors could avoid this problem by measuring AF solely from routine Framingham clinical examinations. Any misclassification would then be nondifferential, leading to a bias toward the null and a conservative estimate of association.

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