Clinical and instrumental comparison between insufficient sleep syndrome and narcolepsy type 1

Insufficient sleep syndrome (ISS) and narcolepsy type 1 (NT1) both feature excessive daytime sleepiness (EDS), yet they differ in etiology and nighttime sleep architecture. We compared clinical characteristics, video-polysomnography (v-PSG), Multiple Sleep Latency Test (MSLT), and actigraphy in ISS and NT1, to better define ISS and differentiate the two disorders. We retrospectively screened patients from a Sleep Medicine Unit who had a confirmed diagnosis of ISS (n = 23) or NT1 (n = 9) and underwent v-PSG, MSLT, and actigraphy. All patients were drug-free, and those with comorbid sleep disorders were excluded. Clinical data were collected through structured interviews, sleep diaries, and standardized questionnaires. Subjective EDS, reported by both ISS and NT1 groups, was similar in severity. MSLT showed that nearly one-third of ISS patients exhibited sleep-onset REM periods (SOREMPs), highlighting the risk of overlap with NT1. In v-PSG, ISS was characterized by high sleep efficiency and a low arousal index; no major differences in sleep parameters emerged between ISS and NT1. Actigraphy provided relevant data: ISS displayed weekday sleep restriction with weekend compensation, whereas NT1 showed fragmented but prolonged nighttime sleep and more frequent daytime naps. Overall, the variability in sleep patterns (time in bed and total sleep time) was more pronounced in ISS on weekends, whereas NT1's hallmark was nighttime fragmentation. While ISS and NT1 overlap in EDS, they differ in the organization of sleep-wake rhythms. Actigraphy, highlighting weekday-weekend changes in ISS and fragmented nighttime sleep in NT1, may be pivotal for differential diagnosis.