New research shows that high rates of sleep disorders -- especially sleep apnea -- plague Iraq and Afghanistan war veterans with post-traumatic stress disorder (PTSD) or head trauma.

Of the 317 soldiers studied at Walter Reed Army Medical Center in Washington, D.C., 56 percent had obstructive sleep apnea, 49 percent had insomnia, 71 percent had fragmented sleep and 87 percent were sleepy during waking hours, researchers found. All of the soldiers who participated in the study had PTSD, traumatic brain injuries,or both.

"We found that sleep disorders appear to break down by presence or absence of injury and by the type of injury," noted Dr. Jacob Collen in a presentation to the American College of Chest Physicians in Honolulu.

Researchers found sleep apnea was significantly more common in PTSD patients without brain trauma or physical injuries.

Insomnia among injured veterans is not a surprise --but the high incidence of sleep apnea found in the study was unexpected, said Dr. Brian Carlin, a sleep medicine specialist at Allegheny General Hospital in Pittsburgh, who was not involved in the study.

"You just wonder now what is the relationship between trauma to the head and sleep disorders."