Sleep apnea harms the brain by breaking down the blood-brain barrier which helps protect brain tissue, according to a new study published in the Journal of Neuroimaging.

Approximately 22 million Americans suffer from obstructive sleep apnea (OSA), which causes breathing to repeatedly stop and start during sleep.

The blood-brain barrier keeps bacteria, infections, and chemicals from getting into the brain, and studies have found that a breakdown in the blood-brain barrier is linked to the brain damage caused by stroke, Alzheimer's, multiple sclerosis, and other conditions.

"We found that the blood–brain barrier becomes more permeable in obstructive sleep apnea, a breakdown that could contribute to brain injury, as well as potentially enhancing or accelerating the damage," said Rajesh Kumar, the study's principal investigator.

"This type of brain injury in obstructive sleep apnea has significant consequences to memory, mood and cardiovascular risk, but physicians and researchers have developed pharmacologic and non-pharmacologic therapeutic strategies to repair blood–brain barrier function in other conditions," said Kumar, who is an associate professor in the departments of anesthesiology and radiological sciences at the UCLA Geffen School of Medicine.

Scientists already knew that OSA damaged the brain in ways that led to high blood pressure, memory loss, depression, and anxiety.

OSA can also lead to stroke, diabetes, and loss of testosterone and endocrine-related problems.

Brain damage is probably caused by the reduction of oxygen due to the continuous interruptions in breathing.

Previous studies have found that high blood pressure and reduced oxygen can affect the blood-brain barrier, which can damage brain tissue, but the new study is the first to show that the breakdown occurs during OSA.

Using a unique MRI procedure to measure the breakdown in the blood-brain barrier, the researchers found that the permeability of the blood–brain barrier was significantly higher in patients recently diagnosed with OSA than it was in healthy people.

"This suggests that besides improving breathing in obstructive sleep apnea patients, we need to repair or improve blood–brain barrier function, perhaps by using treatments already available for other conditions," said Kumar.