By Mary Elizabeth Dallas
"In previous studies, we've seen structural changes in the brain due to sleep apnea, but in this study we actually found substantial differences in ... two chemicals that influence how the brain is working," said lead researcher Paul Macey. He is an associate professor at the UCLA School of Nursing in Los Angeles.
These changes could help explain why people with the disorder develop symptoms that interfere with their daily lives, the investigators suggested. But the study could not prove that these altered levels of brain chemicals actually cause thinking and memory problems.
Moderate to severe sleep apnea affects one in 15 adults. The condition can cause people to experience as many as 30 interruptions in breathing per hour while they sleep. Sleep apnea is also associated with trouble concentrating, memory problems, poor decision-making, depression and stress.
For the study, the researchers examined levels of two brain chemicals: glutamate and gamma-aminobutyric acid, also known as GABA. These chemicals are found in a part of the brain called the insula. This part of the brain combines and coordinates signals from other brain regions to help regulate emotions, thinking, and certain physical functions such as blood pressure and perspiration, the researchers said.
People with sleep apnea have lower levels of GABA and abnormally high levels of glutamate, according to the study published online recently in the Journal of Sleep Research.
While GABA acts as a mood inhibitor, slowing things down and keeping people calm, glutamate has the opposite effect. When glutamate levels are high, the brain is stressed and doesn't work as well, the researchers explained in a university news release.
"It is rare to have this size of difference in biological measures," Macey said. "We expected an increase in the glutamate, because it is a chemical that causes damage in high doses and we have already seen brain damage from sleep apnea.
"What we were surprised to see was the drop in GABA. That made us realize that there must be a reorganization of how the brain is working," he said.
The researchers said their findings highlight the importance of treating sleep apnea.
"What comes with sleep apnea are these changes in the brain, so in addition to prescribing continuous positive airway pressure, or CPAP, a machine used to help an individual sleep easier ... physicians now know to pay attention to helping their patients who have these other symptoms," Macey said. "Stress, concentration, memory loss -- these are the things people want fixed."
Looking ahead, the researchers plan to investigate whether available treatments for sleep apnea help return patients' brain chemical levels to normal.