Event-related potentials in patients with insomnia and sleep-related breathing disorders: evening-to-morning changes

The relationship between event-related potentials (ERPs) and sleep alterations in patients with sleep disorders is still controversial. Whether the ERP alterations are affected by sleep loss and sleep discontinuity can be addressed by studying presleep-to-postsleep changes in ERPs. We investigated if presleep-to-postsleep ERP latencies and amplitudes differ in patients with insomnia and sleep-related breathing disorders and whether these changes are affected by the degree of subjective and objective sleep alterations.

Fifteen patients with a diagnosis of insomnia, 45 patients with sleep-related breathing disorders, and 13 healthy controls were examined. Auditory ERPs were measured in the evening before sleep and in the morning after polysomnography. Subjective sleepiness and sleep quality were assessed by the Epworth Sleepiness Scale and the Saint Mary's Hospital Quality of Sleep Questionnaire.

Analysis of evening-to-morning ERP variations did not reveal significant between-group differences in N100 latency and amplitude or in P200 and P300 amplitudes. Patients with sleep-related breathing disorders had a significant lengthening of P200 and P300 latencies in the morning, compared with controls and insomniacs. A trend to delayed morning P300 was present in patients with insomnia but did not reach statistical significance. The evening-to-morning ERP differences were not significantly related to subjective sleep quality, indexes of sleep fragmentation, or total sleep time.

ERPs are sufficiently sensitive to assess attention dysfunction in patients with sleep disorders when presleep-to-postsleep changes are considered. The lack of relationship between indexes of sleep loss and sleep fragmentation and presleep-to-postsleep ERP changes might suggest that other factors outside sleep alterations affect ERP deterioration in patients with sleep disorders.