Obstructive sleep apnea: brain structural changes and neurocognitive function before and after treatment

The paper assesses the effect of obstructive sleep apnea on brain structure and cognitive performance, and the changes after treatment with Continuous Positive Airway Pressure. The main finding is that cognitive impairment is associated with a decrease of grey-matter volume in specific cerebral regions, and that these can be reversed by treatment with an increase of grey-matter volume in specific hippocampal and frontal brain regions. These changes are significantly correlated with the improvement in specific neuropsychological tests (executive-functioning and short-term memory), underlining the importance of early diagnosis and treatment of sleep apnea. Specific neuropsychological measures represent valuable tools for the assessment of therapy success, and can offer the evidence that adherence to treatment can lead not only to clinical, but also to brain-structural, recovery. Objectives: To investigate the cognitive deficits and the corresponding brain morphology changes in OSA, and the modifications after treatment, using combined neuropsychological testing and Voxel-Based-Morphometry. Methods: 17 treatment-naïve sleep apnea patients and 15 age-matched healthy controls. All underwent a sleep study, cognitive tests and magnetic resonance imaging. After threemonths treatment, cognitive and imaging data were collected to assess therapy efficacy. Measurements and Main Results: Neuropsychological results in pre-treatment OSA showed impairments in most cognitive areas, as well as in mood and sleepiness. These impairments were associated with focal reductions of grey-matter volume in the left hippocampus (enthorinal cortex), left posterior parietal cortex and right superior frontal gyrus. After treatment, we observed significant improvements involving memory, attention and executive-functioning that paralleled grey-matter volume increases in hippocampal and frontal structures. Conclusions: The cognitive and structural deficits in obstructive sleep apnea may be secondary to sleep deprivation and repetitive nocturnal intermittent hypoxemia. These negative effects may be recovered by consistent and throughout treatment. Our findings highlight the importance of early diagnosis and successful treatment of this disorder