Obstructive sleep apnea (OSA), a new research suggests, may cause structural defects in the brain's gray matter, resulting in problems with cognitive functions such as attention and memory.
These brain changes are likely caused by the intermittent oxygen deprivation that occurs in people with OSA, who temporarily stop breathing many times each night.
To determine whether there were quantifiable structural differences in the brains of OSA patients when compared to individuals without OSA, and whether any differences found could be reversed with treatment, Italian researchers compared 17 treatment-na´ve individuals with severe OSA and 15 age-matched controls.
They gathered baseline measurements of brain anatomy using MRI, as well as individual performance on cognitive performance tests that assessed short- and long-term memory, executive functions, constructional abilities, vigilance, attention and abstract reasoning. The subjects also completed the Epworth Sleepiness Scale to assess daytime sleepiness and the Beck Depression Inventory to evaluate mood.
The researchers found significant reductions in gray matter (GM) between OSA and non-OSA subjects. Moreover, the specific locations of the deficits indicated that specific brain functions were more strongly affected than others, including executive function (which controls high-order brain functions such as problem-solving) and abstract reasoning.
"We found reduced GM in the OSA group when compared to the non-OSA group in several key regions of the brain," said Vincenza Castronovo, clinical psychologist at the Sleep Disorders Center, Vita-Salute San Raffaele University and San Raffaele Scientific Institute in Milan, Italy.
"Of particular note were the deficits in the left parahippocampal gyrus and in the left posterior-parietal cortex. We found that these two regions have significant bearing on abstract reasoning and executive function. Deficits in the left posterior-parietal cortex were also shown to be associated with daytime sleepiness."
They also found that on tests, subjects with OSA demonstrated impairments in memory, attention, executive functions and constructional abilities and had higher sleepiness scores.
Remarkably, however, treatment with continuous positive airway pressure (CPAP), seemed to reverse these damages.
The study has been published online ahead of the print edition of the American Thoracic Society's American Journal of Respiratory and Critical Care Medicine.