Even a moderate case of obstructive sleep apnea could be a risk factor for sudden cardiac death.  

In obstructive sleep apnea, breathing is frequently paused during sleep. The condition causes many health complications and increases the risk for stroke and depression, irregular heart beat. Interrupted sleep can also result in drowsiness during the day. People who do not get to sleep for 8 hours at night are at increased risk for car crashes, work-related injuries and other accidents. Poor sleep for longer durations can also lead to cognitive decline.

"The prevalence of obstructive sleep apnea in Western populations is high and will likely only continue to grow given the obesity epidemic and direct relationship between obesity and sleep apnea," said Apoor Gami, M.D., a cardiologist at Midwest Heart Specialists - Advocate Medical Group in Elmhust, Ill and lead author of the study.

Sudden cardiac arrest is when the heart stops beating suddenly, resulting in the brain and other vital organs losing their blood supply. The condition can lead to death if not treated within minutes, says Mayo Clinic.

The study included over 10,700 people who were followed for more than five years. During the study period, 142 people suffered from sudden cardiac death. The most predictors of cardiac death were age (60 years or above), apnea episodes (20 episodes per hour) and an oxygen saturation level of below 78 percent.

Sleep apnea prevents air from flowing into the patient's lungs during sleep. This leads to a drop of oxygen in the blood and raises a person's risk of cardiac death. In this study, researchers found that a blood oxygen drop of 78 percent raises the risk of sudden cardiac death by 80 percent.

"Treating sleep apnea in one person can improve the quality of life of both bed partners and may have the added benefit of helping to prevent cardiovascular disease. If the spouse sees the bed partner stop breathing repeatedly during sleep, this is an important clue that he or she probably has sleep apnea," said Virend K. Somers, M.D., a professor of medicine at Mayo Clinic College of Medicine in Rochester, Minn., and a senior author of the current study, according to a news release.

The study is published in the Journal of the American College of Cardiology.