Sudden cardiac arrest, also called cardiac death, kills some 450,000 Americans a year. And in recent years, the link between obstructive sleep apnea and sudden cardiac arrest has become increasingly clear, with publication of a long-term study bringing the connection into a brighter light.

The study followed 10,701 adult men and women for 15 years. Of those, 78 percent suffered from obstructive sleep apnea. Over the 15-year follow-up period, 142 people experienced sudden cardiac arrest. Some cases were fatal, while others were resuscitated.

The three strongest predictors of risk for sudden cardiac death were being 60 years or older, having low blood oxygen levels, and having at least 20 episodes of apnea per hour.

There is also an association between sleep apnea and atrial fibrillation (AFib), a heartbeat irregularity that causes stroke and other heart-related problems, including sudden cardiac death.

Researchers in Canada reviewed the records of 8,256 adults, average age 47, who were diagnosed with sleep apnea, but had yet to be diagnosed with any heart rate abnormalities, including AFib. They were followed for up to 13 years. During that time, 173 developed AFib serious enough to result in hospitalization.

This study also linked obstructive sleep apnea to a lack of oxygen during sleep, especially in women.