Positive sleep state misperception - a new concept of sleep misperception.

To better define the concept of sleep misperception and analyse a category of patients who overestimate their sleep. At present, a condition of underestimation of sleep is classified as paradoxical insomnia. Overestimation of sleep has also been reported in the past, with no clear reference to corresponding polysomnographic (PSG) findings or its clinical significance. Patients were recruited from the general population undergoing a PSG assessment for a cross-sectional retrospective study in a sleep clinic affiliated with a tertiary health center. A group of patients who overestimated their sleep had mostly non-discriminating PSG findings when compared to patients who underestimated their sleep, and correct estimators. The only parameters that were significantly different were objective sleep duration and efficiency, and, importantly, respective multiple sleep latency test (MSLT) results. The patients who overestimated their sleep had a mean MSLT result of 7.8 min, which indicates moderate daytime sleepiness. Patients who underestimated their sleep and correct estimators had the respective MSLT results of >10 min, making a statistically significant difference. The authors identified a condition opposite the previously described sleep underestimation, and named it 'positive sleep state misperception' (PSSM). The condition is characterised by a gross overestimation of sleep. Inadequate sleep results in a clinically significant excessive daytime sleepiness, which patients were not able to predict. The authors propose a new model that incorporates both ends of the sleep misperception spectrum.