P300 abnormalities in patients with severe sleep apnea syndrome.

We investigated the mechanism of abnormal P300 findings in the patients with severe sleep apnea syndrome (SAS). Compared with controls, SAS patients showed significantly longer latency of P300. Not the mean sleep latency in multiple sleep latency test but the percentage of total periods in which percentage desaturation time fell below 90% to total sleep time correlated with P300 latency in the patients. During nasal CPAP treatment, P300 latency was significantly shortened in the patients under 45 years, while the elderly patients did not show statistical change. We speculated that P300 latencies might be prolonged due to nocturnal hypoxia with SAS and the abnormality might be irreversible, especially in elderly patients.