Improvements in Cognitive Function and Quantitative Sleep EEG in OSA after Six Months of CPAP Treatment.

STUDY OBJECTIVES: Untreated obstructive sleep apnea (OSA) is associated with cognitive deficits and altered brain electrophysiology. We evaluated the effect of continuous positive airway pressure (CPAP) treatment on quantitative sleep electroencephalogram (EEG) measures and cognitive function.

METHODS: We studied 162 OSA patients (age 50±13, AHI 35.0±26.8) before and after 6 months of CPAP. Cognitive tests assessed working memory, sustained attention, visuospatial scanning and executive function. All participants underwent overnight polysomnography at baseline and after CPAP. Power spectral analysis was performed on EEG data (C3-M2) in a sub-set of 90 participants. Relative delta EEG power and sigma power in NREM and EEG slowing in REM were calculated. Spindle densities (events p/min) in N2 were also derived using automated spindle event detection. All outcomes were analysed as change from baseline.

RESULTS: Cognitive function across all cognitive domains improved after six months of CPAP. In our sub-set, increased relative delta power (p<0.0001) and reduced sigma power (p=0.001) during NREM were observed after the 6-month treatment period. Overall, fast and slow sleep spindle densities during N2 were increased after treatment.

CONCLUSIONS: Cognitive performance was improved and sleep EEG features were enhanced when assessing the effects of CPAP. These findings suggest the reversibility of cognitive deficits and altered brain electrophysiology observed in untreated OSA following six months of treatment.