Article ID: 2408oa
This study assessed daytime sleepiness in young adults, including individuals with idiopathic hypersomnia (IH) and narcolepsy (NA), using subjective and objective measures. The participants included adults (N = 42): 13 with IH, 10 with NA, and 19 with healthy controls (HC). We excluded HC participants with a score of ≥11 on the Japanese version of the Epworth Sleepiness Scale. Participants underwent nocturnal polysomnography in a sleep laboratory, followed by administration of the Japanese version of the Karolinska Sleepiness Scale (KSS-J) before each session of the Multiple Sleep Latency Test (MSLT) the next day. We divided HC participants into two groups based on their mean sleep latency on the MSLT: low sleep propensity (low SP; ≥8 min) and high sleep propensity (high SP; <8 min). The high SP group demonstrated a discrepancy between subjective and objective sleepiness. The correlation between KSS-J scores and sleep latency in each nap trial was low and varied by the group. A significant proportion of HC individuals in the high SP group exhibited shorter sleep latency similar to those with IH or NA despite not experiencing subjective sleepiness. We concluded that some healthy individuals show objective signs of sleepiness comparable to those with hypersomnia or narcolepsy, even without reporting subjective sleepiness, underscoring the significance of using subjective and objective measures to assess daytime sleepiness.
