P030 The effects of continuous positive airway pressure (CPAP) therapy in moderate to severe obstructive sleep apnea (OSA): A high-density electroencephalography (EEG) study

INTRODUCTION: A previous high-density EEG investigation in OSA showed regional sleep EEG deficits particularly slow wave activity (SWA) in the parietal region. It is unclear whether CPAP treatment can reverse local sleep EEG abnormalities, and whether any recovery is related to improved cognitive function. METHODS: Fifteen males with moderate-severe OSA (age 50.4±6.5yrs, AHI 51.7±23.5/h) underwent polysomnography with 256-channel high-density EEG at baseline and following 3 months of CPAP. Tasks assessing cognitive performance and sleep-dependent memory were administered. Topographical spectral power maps were calculated for standard frequency ranges for sleep stages. Differences in normalized power between baseline and treatment were determined by statistical nonparametric mapping. RESULTS: In 11 CPAP compliant patients (data loss: intolerant of CPAP[n=3]/high-density EEG [n=1]), total sleep time did not change after CPAP but N1 (baseline vs. treatment: 66.9 vs. 39.5 mins, p=0.008) and N2 (195.0 vs. 150.6 mins, p=0.002) sleep was lower and N3 (89.8 vs. 128.7 mins, p=0.003) was higher. Topographic high-density EEG analysis revealed a regional increase in SWA (1–4.5Hz) during N3 sleep in a cluster of 22 electrodes overlying the parietal cortex (paired t-test, t(10)=-3.9, p=0.0029). The change in N3 SWA in the parietal cluster after CPAP was correlated with improved overnight procedural memory on the motor sequence task (rho=0.79, p=0.03) and better executive functioning (Stroop accuracy, rho=0.73, p=0.01). CONCLUSION: CPAP treatment reduces localised deficits in sleep EEG, and specific regional recovery relates to short-term improvements in memory and executive function. These data also highlight the potential for long-term therapeutic effects on cognitive outcomes.