Visual dysfunction and computational sleep depth changes in obstructive sleep apnea syndrome

The aims of this study are to clarify whether patients with obstructive sleep apnea syndrome (OSAS) have a decline in verbally or visually-based cognitive abilities and whether the possible decline is related to particular sleep depth changes. In addition, the effect of continuous positive airway pressure (CPAP) on the possible changes is investigated. Fifteen OSAS patients and 15 healthy controls joined two full-night polysomnographies, including a computational measure of deep sleep percentage (DS%) bilaterally from the frontal, central and occipital channels, and a neuropsychological assessment. After a 6-month CPAP the patients underwent one more full-night polysomnography with computational DS% analysis and a neuropsychological assessment. At the baseline, the OSAS patients had poorer performance in the Picture Completion, in the Digit Symbol and in copying the Rey-Osterrieth Complex Figure Test (ROCFT) compared to the controls. The patients also showed reduced DS% in all 6 electrographic (EEG) channels compared to controls. The patients had an inter-hemispheric difference showing less deep sleep in the right hemisphere than in the left hemisphere both frontopolarly and centrally, while the controls showed this inter-hemispheric difference only frontopolarly. After CPAP the patients still had poorer performance in the Picture Completion and in the ROCFT. The patients continued to show reduced DS% in all 3 channels of the right hemisphere and occipitally in the left hemisphere, also the inter-hemispheric difference frontopolarly and centrally remained. OSAS patients have mild visually based cognitive dysfunction and reduced amount of deep sleep in the right hemisphere even after CPAP.