|Brain maps showing compromised blood-brain barrier function in one person with obstructive sleep apnea (left) and one person with a healthy brain. Regions with yellow-to-red areas represent an intact blood-brain barrier; regions with blue-scale colors indicate an altered blood-brain barrier.
Image: Courtesy of Dr. Rajesh Kumar
UCLA researchers have reported the first evidence that obstructive sleep apnea contributes to a breakdown of the blood-brain barrier that plays an important role in protecting brain tissue by limiting harmful bacteria, infections and chemicals from reaching the brain. The discovery could lead to new approaches to treat obstructive sleep apnea, which causes frequent interruptions in breathing during sleep because the airways narrow or become blocked.
Studies have found that a compromised function of the blood-brain barrier is associated with significant brain damage in stroke, epilepsy, meningitis, multiple sclerosis, Alzheimer’s disease 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,” says Rajesh Kumar, PhD, associate professor of anesthesiology and a member of the UCLA Brain Research Institute. “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.”
From research conducted at UCLA over the past 12 years, experts have learned that the gasping during the night that characterizes obstructive sleep apnea can damage the brain in ways that lead to high blood pressure, depression, memory loss and anxiety. It also can cause extreme daytime sleepiness and can lead to stroke, diabetes, loss of testosterone and endocrine-related problems.
The damage to the brain likely stems, in part, from the reduction of oxygen to the body as a result of the repeated breathing interruptions. But doctors do not yet fully understand exactly what causes the brain injury and how it progresses. While previous studies have found that reduced exposure to oxygen and high blood pressure can affect the blood-brain barrier, which in turn can introduce or enhance brain-tissue injury, Dr. Kumar and his colleagues are the first to show that this breakdown occurs in obstructive sleep apnea.
The study was conducted with a magnetic resonance imaging procedure that uses the brain’s own blood and fluids to measure the breakdown of the blood-brain barrier. In the new study, the researchers found that in patients who recently had been diagnosed with obstructive sleep apnea and not yet treated, the permeability of the blood-brain barrier was significantly higher 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,” Dr. Kumar says.
He noted that the study was small — nine people with obstructive sleep apnea were compared to nine healthy controls. Now, in addition to confirming these findings in a larger population of patients with obstructive sleep apnea, the researchers are planning to study whether or not strategies known to be effective in overcoming blood-brain barrier breakdown in people who have had a stroke and other neurological conditions also can help minimize brain injury in people with obstructive sleep apnea or other long-standing respiratory problems.
“Water Exchange across the Blood-Brain Barrier in Obstructive Sleep Apnea: An MRI Diffusion-weighted Pseudo-continuous Arterial Spin Labeling Study,” Journal of Neuroimaging, September 1, 2015