Polysomnographic study of nocturnal sleep in idiopathic hypersomnia without long sleep time

Summary We investigated nocturnal sleep abnormalities in 19 patients with idiopathic hypersomnia without long sleep time ( IH ) in comparison with two age‐ and sex‐ matched control groups of 13 normal subjects ( C ) and of 17 patients with narcolepsy with cataplexy ( NC ), the latter considered as the extreme of excessive daytime sleepiness ( EDS ). Sleep macro‐ and micro‐ (i.e. cyclic alternating pattern, CAP ) structure as well as quantitative analysis of EEG , of periodic leg movements during sleep ( PLMS ), and of muscle tone during REM sleep were compared across groups. IH and NC patients slept more than C subjects, but IH showed the highest levels of sleep fragmentation (e.g. awakenings), associated with a CAP rate higher than NC during lighter sleep stages and lower than C during slow wave sleep respectively, and with the highest relative amount of A 3 and the lowest of A 1 subtypes. IH showed a delta power in between C and NC groups, whereas muscle tone and PLMS had normal characteristics. A peculiar profile of microstructural sleep abnormalities may contribute to sleep fragmentation and, possibly, EDS in IH .