Adults with obstructive sleep apnea (OSA), a condition in which airways become blocked during sleep and breathing stops for brief periods, are more likely to die suddenly from cardiac causes while they are asleep, a pattern that is opposite to that of the general population, new research indicates.

Dr. Apoor S. Gami and colleagues reviewed death records of 112 subjects who died suddenly from cardiac causes after undergoing sleep studies at the Mayo Clinic Sleep Disorder Center in Rochester, Minnesota, between 1987 and 2003. They report their findings in The New England Journal of Medicine for March 24.

Seventy-eight of the patients had been diagnosed with OSA. Sudden cardiac death between midnight and 6:00 a.m. occurred in 46 percent of those with OSA and 21 percent of those with other diagnoses. In the general population, about 16 percent of cardiac deaths occur during sleep, the authors note.

“Usually sleep hours are thought to be a protective period,” Gami told AMN Health, “but our data suggest a reason why individuals may have sudden death during sleep.” The team found that death during sleeping hours was correlated with severity of OSA.

Continuous positive airway pressure or CPAP is sometimes used as a treatment for OSA, the investigators note. While their “look-back” study cannot provide any firm conclusions about the role of CPAP in preventing sudden cardiac death during sleep, the researchers say CPAP is associated with several mechanisms that could reduce the risk of sleep apnea-induced Heart Disease.

“CPAP first of all reverses the apneic episodes themselves, and it also reverses hypoxemia (low blood oxygen levels) that occurs during the night,” Gami said. Also, CPAP therapy has been shown to reduce blood pressure surges that occur during the night.

SOURCE: The New England Journal of Medicine March 24, 2005.