Differences in Sleep Spindle Characteristics Between Children With Narcolepsy and Those With Other Causes of Subjective Sleepiness.

Central disorders of hypersomnolence are characterised by excessive daytime sleepiness. There has been growing interest in analysing sleep micro-architecture, to further understand how sleep is affected by these conditions. We investigated if sleep spindle activity differed between children with narcolepsy, idiopathic hypersomnolence (IH) and subjectively sleepy children with a non-diagnostic multiple sleep latency test, and individually age- and sex-matched controls. Twenty eight children with narcolepsy, 11 with IH and 26 with subjective sleepiness (aged 6-19 years) were included. Spindle activity was characterised as spindle density (number of spindles/min) and intensity (density × average duration) of central (C4) and frontal (F4) EEG electrodes for Slow and Fast spindles and combined (Slow&Fast) across the sleep period and also when separated into NREM sleep periods (NREMP) across the night. C4 Slow and Fast and F4 Slow spindle duration was longer in children with narcolepsy compared to their controls (p < 0.05 for all comparisons) and to those with subjective sleepiness (p < 0.05). In the children with narcolepsy and subjective sleepiness C4 spindle intensity was greater (p < 0.05 for both groups) compared to controls. C4 spindle density and intensity were lower at the beginning compared to the end of the night in the children with narcolepsy and subjective sleepiness (p < 0.05 for both groups). There were no relationships between spindle activity and parental reports of daytime sleepiness. Spindle characteristics differed between children with narcolepsy compared to controls and to children with undiagnosed subjective sleepiness. Our findings may aid in distinguishing between groups of children referred for assessment of excessive daytime sleepiness.