Are unrefreshing naps associated with nocturnal sleep architecture specificities in idiopathic hypersomnia?

Study Objectives Unrefreshing naps are supportive clinical features of idiopathic hypersomnia (IH) and are reported by more than 50% of IH patients. They are, however, not mandatory for the diagnosis, and their pathophysiological nature is not understood. This study aimed at verifying whether IH patients with and without unrefreshing naps constitute two subtypes of IH based on their demographic/clinical characteristics, and sleep architecture. Methods One hundred twelve IH patients underwent a polysomnography (PSG) followed by a multiple sleep latency test (MSLT). They completed questionnaires on excessive daytime sleepiness, mood, and sleep quality. They were met by sleep medicine physicians who conducted a semi-structured clinical interview and questioned them on refreshing aspects of their naps. Patients who reported unrefreshing naps were compared to patients reporting refreshing naps on questionnaires, MSLT and PSG variables, with age as a covariable. As sensitivity analyses, we performed the same comparisons in participants presenting objective markers of IH and those diagnosed with IH based only on clinical judgment (subjective IH), separately. Results In the whole sample, 61% of patients reported unrefreshing naps. These participants had less awakenings, a lower percentage of N1 sleep, less sleep stage transitions, and a higher percentage of REM sleep on the nighttime PSG compared to the refreshing naps subgroup. When subjective and objective IH patients were tested separately, more group differences were observed on PSG for subjective IH patients. Conclusions Patients with unrefreshing naps have less fragmented sleep compared to those with refreshing naps. Future studies should investigate whether this group difference indicates a weaker arousal drive.

Automated summary

This study aimed to investigate whether patients with unrefreshing naps and patients with refreshing naps are two subtypes of idiopathic hypersomnia (IH) based on their demographic/clinical characteristics and sleep architecture. The results showed that patients reporting unrefreshing naps had less fragmented sleep compared to those reporting refreshing naps, with fewer awakenings, a lower percentage of N1 sleep, fewer sleep stage transitions, and a higher percentage of REM sleep on the nighttime PSG. This suggests that patients with refreshing naps experience more disrupted sleep. Further research is needed to understand whether this difference indicates a weaker arousal drive.