A study in the Sept. 1 issue of the journal Sleep examined the brain activity of people with obstructive sleep apnea.
The study from Italy involved 17 men with OSA who had never been treated. They had an average age of 44 years.
At the start of the study the men underwent a neuropsychological evaluation. They were tested in areas such as learning, recall, attention and vigilance. They also completed a verbal working-memory task during a functional MRI brain scan.
They were evaluated again after three months of treatment with nightly CPAP therapy. Their performance and brain activity were compared with 15 healthy controls.
Results show that the men with OSA had neurocognitive impairments prior to treatment. Most of these deficits improved after treatment with CPAP.
But during the working-memory task there was no significant difference in the cognitive performance of untreated men with OSA and healthy controls; their accuracy and response times were similar. Men with OSA also showed similar levels of performance before and after treatment with CPAP.
There was a large overlap in the pattern of brain activity in OSA men and healthy controls during the working-memory task. But some regions were less active in men with untreated OSA; additional brain regions also showed increased activation. Then after three months of CPAP therapy, men with OSA showed decreases in the activation of certain brain regions.
What does this mean? The authors suggest that the results support the “compensation hypothesis.”
OSA may cause brain dysfunction. To maintain performance the brain has to compensate for this loss. So it “recruits help” from other brain regions.
Treatment with CPAP therapy helps restore a normal pattern of brain activation. Then the brain no longer needs extra help to preserve cognitive performance.
A similar study of people with insomnia was presented in June at SLEEP 2009; it found that adults with primary insomnia have increased brain activation during a working-memory task.
In March the Sleep Education Blog reported that OSA may cause brain damage; brain imaging studies have found a loss of brain tissue in people with sleep apnea.