The worst danger of sleep apnea might not be losing sleep. New research shows the condition can damage parts of the brain.

An estimated 12 to 20 million Americans suffer from varying degrees of sleep apnea.

The condition causes muscles in the throat to relax and cut off the airway. In some cases, people can stop breathing for several minutes.

"I would wake up in the night, gasping for air," sleep-apnea patient Jim Reynolds said.

Reynolds said apnea zapped his energy and focus. Dr. Ronald Harper, with UCLA, found that Reynolds also suffered from another common side effect of sleep apnea: short-term memory loss.

"If you imagine what it's like when you go through a night without any sleep, the next day you're foggy," Reynolds said. "Imagine what it's like going through 10 years of that."

Doctors have long thought sleep deprivation caused short-term memory loss. However, Harper found that much more goes on in the minds of sleep-apnea patients.

Mammary bodies in the brain store memories, but in sleep-apnea patients, that area of the brain shrinks significantly. Constant oxygen deprivation might be the cause.

Researchers are experimenting with giving sleep-apnea patients a pill used to treat alcoholics with memory loss.

Until the results of that trial are known, the best treatment is sleeping with a breathing assist machine and daily exercise.

"We're finding brain areas do recover, especially after exercise," Harper said.

Reynolds said that prescription has ameliorated his symptoms. "My sharpness during the day improved tremendously," he said.

However, Reynolds said his short-term memory has not returned fully – and he wonders if it ever will.