Narcolepsy type 1 features across the life span: age impact on clinical and polysomnographic phenotype

Narcolepsy type 1 (NT1) is a chronic neurological disorder typically arising during adolescence and young adulthood. Recent studies demonstrated that NT1 presents with age-specific features, especially in children. With this study we aimed to describe and to compare the clinical pictures of NT1 in different age groups.

In this cross-sectional, multicenter study, 106 untreated patients with NT1 enrolled at the time of diagnosis underwent clinical evaluation, a semistructured interview (including the Epworth Sleepiness Scale), nocturnal video-polysomnography, and the Multiple Sleep Latency Test. Patients were enrolled in order to establish 5 age-balanced groups (childhood, adolescence, adulthood, middle age, and senior).

The Epworth Sleepiness Scale score showed a significant increase with age, while self-reported diurnal total sleep time was lower in older and young adults, with the latter also complaining of automatic behaviors in more than 90% of patients. Children reported the cataplexy attacks to be more frequent (> 1/d in 95% of patients). "Recalling an emotional event," "meeting someone unexpectedly," "stress," and "anger" were more frequently reported in adult and older adult patients as possible triggers of cataplexy. Neurophysiological data showed a higher number of sleep-onset rapid eye movement periods on the Multiple Sleep Latency Test in adolescent compared to senior patients and an age-progressive decline in sleep efficiency.

Daytime sleepiness, cataplexy features and triggers, and nocturnal sleep structure showed age-related difference in patients with NT1; this variability may contribute to diagnostic delay and misdiagnosis.