Daytime sleepiness and EEG spectral analysis in apneic patients before andafter treatment with continuous positive airway pressure

Background: Obstructive sleep apnea syndrome (OSAS) is characterized by rec urrent apneas during sleep, resulting in repetitive hypoxemic episodes and interruptions of the normal sleep pattern. A previous study showed EEG slow ing tie, a higher ratio of delta + theta frequencies to alpha + beta freque ncies on EEG) during rapid eye movement (REM) sleep and wakefulness in untr eated OSAS patients. Study and objectives: To determine whether EEG slowing is reversible with c ontinuous positive air pressure (CPAP) treatment and to verify whether the persistence of excessive daytime sleepiness (EDS) is correlated with residu al slowing of the EEG. Patients: Ten healthy subjects (9 men and 1 woman) and 14 patients with mod erate-to-severe OSAS (13 men and 1 woman) were studied before and after 6 m onths of treatment with CPAP. Results: Untreated OSAS patients showed EEG slowing in frontal and central cortical regions during both wakefulness and during REM sleep compared to h ealthy control subjects. This EEG slowing was found to be independent of ti me spent with arterial oxygen saturation < 90%, severity of OSAS, or mean s leep latency as determined by the multiple sleep latency test. CPAP treatme nt was found to correct the EEG slowing for both REM sleep and wakefulness. Daytime sleepiness also greatly improved with treatment, but some degree o f somnolence remained. Conclusion: CPAP treatment was found to correct the EEG slowing that was ob served in untreated OSAS patients. Persistent EDS may be related to persist ent obesity after CPAP treatment.