Homeostatic sleep regulation in patients with idiopathic hypersomnia

Objective: To determine whether the spectral activity during sleep of patients with idiopathic hypersomnia (IH) differs from that of healthy subjects. Methods: Spectral analysis of the electroencephalogram (EEG) was performed in 10 patients with IH and in 10 age-matched control subjects. We compared the time course of absolute power for slow wave activity (SWA: 0.75–4.5 Hz), and for theta, alpha, sigma and beta bands for the first 4 non-rapid-eye movement (NREM) episodes. Results: Compared to controls, IH patients had less SWA across the night although the exponential decay was preserved. The fall in SWA was statistically significant for the first two NREM episodes only. The lower power of SWA was related to lower amounts of stages 3 and 4 of NREM sleep during the sleep episodes. No correlation was found between SWA during the night and the mean sleep latency on the multiple sleep latency test (MSLT). Conclusions: These results showed that, in IH patients, the homeostatic sleep regulatory mechanisms are preserved but the sleep pressure, indicated by SWA, is lower.