Sleep duration and its association with sleepiness and depression in "ronin-sei" preparatory school students

The Japanese word "ronin-sei" refers to a student who has failed their university entrance examination and is preparing to re-take the examination in the following year. We aimed to determine how sleep duration is associated with daytime sleepiness or depression in ronin-sei because impaired daytime performance is known to result from sleep deprivation.

The participants in this cross-sectional study were 1075 ronin-sei and 285 university students. Sleepiness and depressive symptoms were assessed using the Epworth Sleepiness Scale (ESS) and the Center for Epidemiologic Studies Depression Scale (CES-D), respectively.

Ronin-sei had significantly shorter sleep duration and earlier bed- and rise-times than university students. There was no significant difference in CES-D between the groups; however, the ESS score of university students was significantly higher than that of ronin-sei. Ronin-sei who slept for 5 to <6h had higher ESS scores than those who slept for 6 to <7h. The mean CES-D score in ronin-sei who slept <5h was significantly higher than in those who slept for 5 to <6h, from 6 to <7h, and from 7 to <8h. Ronin-sei who slept for more than 8h also had higher depression scores.

Sleep deprivation appears to be common among ronin-sei. Furthermore, a U-shaped relationship was found between sleep duration and depressive symptoms, revealing that ronin-sei who had too little or too much sleep were more likely to exhibit an increase in depressive symptoms.