Patients with obstructive sleep apnea may be at greater risk of developing atrial fibrillation, or irregular heartbeat, new research finds.

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Researchers say that OSA could increase the risk of atrial fibrillation.

Lead author Dr. Tetyana Kendzerska, Ph.D., of the University of Ottawa in Canada, and colleagues came to their findings by analyzing the medical records of more than 8,000 adults.

The results were recently presented at the American Thoracic Society Conference 2017, held in Washington, D.C.

Obstructive sleep apnea (OSA) is a condition characterized by pauses in breathing during sleep, due to a partial or complete blockage of the upper airway.

According to the American Sleep Apnea Association, more than 22 million people in the United States are affected by sleep apnea, with OSA being the most common form.

Patients with OSA are more likely to have high blood pressure, or hypertension, which is a major risk factor for heart disease and other cardiovascular conditions.

When it comes to atrial fibrillation (A-fib), however, the new study from Dr. Kendzerska and team finds that the risk of this condition may be higher for patients with OSA, independent of high blood pressure.

A-fib is a condition characterized by an irregular, often rapid heartbeat, which can increase the risk of stroke, heart failure, and other complications.

Abnormal oxygen saturation level during sleep may raise A-fib risk

The study involved 8,256 adults of an average age of 47 years. All adults had suspected OSA at study baseline, but they had not been diagnosed with A-fib or any other condition involving irregular heartbeat.

The researchers reviewed the medical records of each patient. They looked at markers of OSA severity, including how many partial or complete breathing pauses occurred during each hour of sleep, and how much time patients spent with abnormal oxygen saturation, defined as an oxygen saturation below 90 percent.

During a median follow-up period of 10 years, a total of 173 patients developed A-fib that required hospitalization.

The researchers found that patients with abnormal oxygen saturation were at a significantly greater risk of developing A-fib during follow-up than those with a normal oxygen saturation level; the number of breathing pauses during each hour of sleep did not appear to affect A-fib risk.

The researchers came to these findings after accounting for numerous risk factors for A-fib, including age, sex, smoking status, and even blood pressure.

"Hypertension may be the causal pathway between OSA and AF [atrial fibrillation], so including it might have diminished the association between OSA and AF," says Dr. Kendzerska.

"However, in our secondary analysis, we did control for hypertension," she adds, "and the association between oxygen desaturation and AF remained significant, suggesting that OSA can directly cause AF without the intermediate step of developing hypertension."

Why might OSA increase A-fib risk?

The researchers are unable to describe the precise mechanisms that drive the link between OSA and increased risk of A-fib, but senior author Dr. Richard S. Leung, of the University of Toronto in Canada, has some theories:

"Greater endothelial dysfunction, higher propensity to develop pulmonary and systemic hypertension and impaired heart rate responses to autonomic challenges in women with OSA may explain these findings," he says, "but further studies are needed to confirm this finding and understand the potential mechanisms."

The researchers admit that there are some limitations to their study. For example, they did not have data on patients' adherence to treatment with continuous positive air pressure, which is the primary therapy for patients with OSA.

What is more, the team was unable to determine whether or not patients were being treated for high blood pressure.

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