Patients with atrial fibrillation are more likely to have obstructive sleep apnea than other cardiology patients, according to an article in the July 13th rapid access issue of Circulation.

Obstructive sleep apnea, a known contributor to myocardial infarction and stroke, is characterized by repeated interruption of breathing during sleep. The prevalence of sleep apnea is directly related to body mass index, and the incidence rate increases with increasing obesity.

Shared risk factors for atrial fibrillation and obstructive sleep apnea include male gender, hypertension, congestive heart failure and coronary artery disease, but the actual prevalence of sleep apnea among atrial fibrillation patients is unknown, said senior author Virend K. Somers, M.D., PhD.

“Because sleep apnea is significantly underdiagnosed and treatment may lower the risk of recurrent atrial fibrillation, determining its prevalence in patients with atrial fibrillation can be very important,” he said.

In the current study, 151 patients with atrial fibrillation and 312 general cardiology patients answered a questionnaire regarding snoring, daytime sleepiness, body mass index, and hypertension to identify risk of sleep apnea. Almost half (49 percent) of the atrial fibrillation patients were identified as high risk for sleep apnea compared with about one third (32 percent) of general cardiology patients. Patients with atrial fibrillation were twice as likely to have sleep apnea (2.19 odds ratio).

“Atrial fibrillation is predicted to affect more than 5 million people by the year 2050. The coinciding epidemics of obesity and atrial fibrillation underscore the clinical importance of these results,” said Apoor S. Gami, MD, lead author of the study.

Another novel observation was that the association of obstructive sleep apnea with atrial fibrillation was greater than the association of sleep apnea with its traditional risk factors such as body mass index, neck circumference, and hypertension, Gami said. The study suggests that it is not only common diseases associated with both conditions that may lead to atrial fibrillation, but there may be a unique interaction between the pathophysiologies of sleep apnea and atrial fibrillation.

When sleep apnea interrupts breathing, blood oxygen level drops while carbon dioxide increases. The sympathetic nervous system is activated. Also, forceful breathing efforts through the obstructed airway may result in dramatic pressure shifts across the cardiac chambers. These reactions, if untreated over time, may predispose to atrial fibrillation.

Although sleep apnea is ideally diagnosed with overnight observation in a sleep lab, the researchers said the questionnaire was able to very reliably predict who did or did not have sleep apnea. The authors recommend that the possibility of obstructive sleep apnea be considered in all patients with atrial fibrillation and screening might be warranted in dysrhythmia patients who are also obese or have hypertension.