Aquaporin‐4 in Narcolepsy Type 1: Investigation of Perivascular Fluid Movement in Sleep Disorders

Narcolepsy type 1 (NT1) is caused by the loss of hypocretin-1 leading to excessive daytime sleepiness and cataplexy. Additionally, disrupted nighttime sleep has become an increasingly recognized feature of NT1. As the glymphatic fluid movement has been linked to sleep architecture, we investigated cerebrospinal fluid (CSF) Aquaporin-4 (AQP4) as potential biomarker for perivascular fluid exchange processes in 133 NT1 patients, 145 patients with other sleeping disorders, and 62 controls. NT1 patients showed lower CSF AQP4 concentrations compared to both control groups (p < 0.0001 and p = 0.01). AQP4 levels were correlated to the CSF hypocretin-1 levels. These data suggest potential brain fluid barrier alterations in NT1.