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.
Bajaj HS, Hillson SD. Obesity and the Risk of New-Onset Atrial Fibrillation. JAMA. 2005;293(16):1974–1975. doi:10.1001/jama.293.16.1974-c
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