According to new study by researchers at the UCLA School of Nursing, individuals with sleep apnea have significant changes in the levels of two important brain chemicals; this finding could explain why many of them have symptoms that impact their day-to-day lives. The study authors explain that one in 15 adults has moderate to severe obstructive sleep apnea, a disorder in which an individual’s breathing is frequently interrupted during sleep, as many as 30 times per hour. People with sleep apnea also often report problems with thinking such as poor concentration, difficulty with memory and decision-making, depression, and stress.
The investigators examined the levels of two neurotransmitters, glutamate and gamma-aminobutyric acid (GABA) in a brain region called the insula, which integrates signals from higher brain regions to regulate emotion, thinking and physical functions such as blood pressure and perspiration. They found that individuals with sleep apnea had decreased levels of GABA and unusually high levels of glutamate.
GABA is a chemical messenger, which functions as an inhibitor in the brain; it can slow things down; thus, instilling calmness. GABA affects mood and is involved in the production of endorphins. In contrast, glutamate is an accelerator; when glutamate levels are high, the brain is working in a state of stress, and consequently does not function as effectively. High levels of glutamate can also be toxic to nerves and neurons.
“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 these two chemicals that influence how the brain is working,” noted lead researcher Paul Macey, an associate professor at the UCLA School of Nursing. He added that he and his colleagues were surprised by the differences in the GABA and glutamate levels. He explained, “It is rare to have this size of difference in biological measures. 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.”
Macey noted that the findings are, in a way, encouraging. He said, “In contrast with damage, if something is working differently, we can potentially fix it.” He added that the link between sleep apnea and changes in the state of the brain is important news for clinicians. He explained, “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, which is the gold standard treatment for sleep disturbance, physicians now know to pay attention to helping their patients who have these other symptoms. Stress, concentration, memory loss — these are the things people want fixed.”
The researchers have planned future studies that have the goal of determining whether treating the sleep apnea, using CPAP or other methods, returns patients’ brain chemicals back to normal levels. If not, they will search for treatments could be more effective. They are also studying the impacts of mindfulness exercises to see if they can reduce glutamate levels by calming the brain.
The study was conducted at the UCLA Sleep Disorder Center and published online in the Journal of Sleep Research on February 4.