This study investigated the bedroom environment and parental awareness of adolescents and its association with adolescents’ sleep. We hypothesized that improving the bedroom environment would help resolve sleep-related problems among adolescents. However, contrary to our expectations, no significant association was found between the bedroom environment and sleep. More notably, our results indicate that social schedule and parental awareness have a greater influence on adolescent sleep than bedroom environment. One key finding was the positive correlation between wake-up time on weekdays and morning departure time for both junior and high school students. Among junior high school students, earlier departure time was associated with earlier bedtime on weekdays. However, for high school students, despite an earlier morning departure time, bedtime did not change. Furthermore, the correlation between morning departure time and sleep duration was stronger for high school students (rs = 0.32) than for junior high school students (rs = 0.12). High school students compensated for insufficient sleep on weekdays by extending their weekend sleep duration. Additionally, insufficient sleep and skipping breakfast were more prevalent among the high school students. For junior high school students, an earlier morning departure time may be manageable by going to bed earlier, suggesting a potential for self-directed solutions. However, this may not be feasible for high school students, who often face longer commutes due to reliance on trains or buses, resulting in earlier departure time compared to junior high school students. Our study also revealed that high school students departed significantly earlier, although both junior and high school students left for school around 07:30 h–07:40 h. The wake-up time for both groups was approximately 06:30 h. According to the recommended sleep duration [2], adolescents in this age group need 8–10 h of sleep. To meet this recommendation, students would need to go to bed between 20:30 h and 22:30 h if they awoke at 06:30 h. However, the results of this study showed that high school students went to bed around 23:30 h, making it unrealistic to encourage bedtime between 20:30 h and 22:30 h. This discrepancy is partly due to the biological tendency of adolescents, particularly those in their late teens, to shift toward a later chronotype, making it difficult for them to fall asleep earlier [1]. Therefore, aligning school schedules with biological rhythms is crucial. Previous studies have shown that delayed high school start times improve sleep, reduce daytime sleepiness [16, 17] and enhance academic performance [18]. Later start times have also been linked to lower migraine frequency [19]. In Hong Kong, a 1-h delay in school start time was associated with improved sleep duration, mental health, and life satisfaction, as well as increased breakfast consumption and decreased unexcused tardiness, absences, and clinic visits [20]. However, another study suggested that, although later start times may delay sleep onset, they do not necessarily extend sleep duration, suggesting that delayed start times may be a necessary but insufficient measure to ensure adequate sleep [21]. Although society expects students to have sufficient sleep time, simply providing sleep time may not resolve the issue of insufficient sleep. In Japan, where sleep duration is the shortest internationally [22], it is necessary to establish an understanding of and practice to ensure adequate sleep duration, both socially and individually. Furthermore, longer commuting time has been linked to depression among high school students in Japan [23], highlighting the need for measures that allow sufficient sleep and support for overall health. It is essential to raise awareness regarding the importance of mental health and sleep hygiene among schools, parents, and students. Schools should consider students’ biological rhythms when planning school schedules, while personal strategies that students and parents can adopt include ensuring that the school’s schedule allows for the maintenance of a healthy lifestyle, including sufficient sleep duration, when selecting schools.

The study found that insufficient sleep, late chronotype, and skipping breakfast were associated with parental attention to ensure an adequate amount of sleep. A previous review of parental factors influencing adolescent sleep suggested that bedtime rules and restrictions on the nighttime use of electronic devices are linked to sleep duration in adolescents [24]. This study further suggests that parents may play a key role in shaping their adolescents’ sleep habits, as there is a notable similarity in sleep patterns between parents and their adolescents, along with the understanding that adolescent behavioral patterns develop based on social learning theory. Therefore, promoting healthy sleep habits among parents is crucial for interventions aimed at addressing sleep-related problems among adolescents. A study conducted in Dutch high schools found that parental subjective norms and perceived behavioral control were associated with longer sleep duration in adolescents [25]. These findings suggest that sleep education for both students and their parents could be an effective intervention to promote adequate sleep durations. Figure 1 shows that parental awareness of sleep issues was weaker among high school students than junior high school students, which aligns with the increasing independence of adolescents in this age group. However, it is noteworthy that parental concern about sleep-related.

problems still plays a role among high school students, underscoring the continued importance of parental involvement even as adolescents strive for greater autonomy. Ensuring adequate sleep, maintaining a healthy chronotype, emphasizing the importance of breakfast, and fostering healthy lifestyle habits at a young age are crucial for long-term health and wellness. Therefore, these factors are an important public health concern.

Contrary to our hypothesis, the association between the bedroom environment (e.g., window direction, curtain type, and lighting color) and sleep was not confirmed. Instead, this study found that social schedule and parental awareness had a more significant impact on sleep. Although an association was observed between lighting color and skipping breakfast among junior high school students, the reasons for this relationship remain unclear. Future research should incorporate objective measures such as light intensity (lux) and other environmental factors.

This study has several limitations. First, as the survey was conducted by an online research company, the generalizability of the findings may be limited. Second, although we assessed the sleep pattern of junior and high school students based on parent-reported data, which may not fully reflect the students’ actual sleep behaviors, a previous study have shown that parent reports tend to overestimate sleep duration compared to objective measures such as actigraphy [26]. Considering this, it is possible that the prevalence of insufficient sleep among adolescents may be underestimated. Nevertheless, the differences in sleep patterns and sleep-related problems observed between junior and high school students were consistent with well-established findings, suggesting that the results are reasonable and reliable. Furthermore, our study provides valuable insights into bedroom environments and parental awareness, contributing important evidence to this field despite inherent limitations. Third, a comprehensive understanding of adolescents’ sleep would require direct information on their daily life, school activities, and time use. Therefore, future research is needed to conduct bedroom environment surveys targeting both adolescents and their parents, taking into account overall lifestyle and physical and mental health.