The main results of this study were the correlations between sleep and the HRQoL-dimensions psychological well-being, school environment, and social support and peers. It is difficult to say what comes first, sleep disturbances or poor HRQoL. Certainly, they are associated with each other and likely connected with each other like a vicious circle. Sleep disturbances in children have previously been reported to be associated with emotional problems such as anxiety , leading to late bedtimes, poor sleep duration, and frequent night awakenings [24,25]. In a systematic review, longer sleep duration has been found to be related with better emotional regulation and quality of life in 5–17-year-old children . The overall sleep duration for the children in the present study was 9–11 hours per night, which is in line with general sleep duration recommendations [2,27], but contrasts with other studies describing less sleep duration in the latest decennium [7,28]. Longer sleep duration was seen in younger children compared to older. Biological rhythm of sleep and waking is regulated through both circadian and homeostatic processes, but also active and complex neurophysiologic processes that change over the life course, especially in the first five years, leading to longer sleep duration . Furthermore, it could be expected that older children have later bedtimes than younger children. According to Norell-Clarke and Hagquist , there has been a change in bedtime over time, with later bedtimes, less sleep, and sleep onset difficulties in 11-year-old children in Sweden. However, the children in our study were below the age of 11 years and cannot be fairly compared to the above-mentioned study. The widespread possible answer (3 hours) in the PISI (item no. 6: total hours of sleep on most nights) should also be taken into consideration. Therefore, the PISI may be more appropriate for screening sleep problems such as SOP and SMP, than measuring subjective sleep duration, i.e. total hours of sleep.
In present study, problems maintaining sleep were related to the HRQoL-dimension poor school environment, which includes cognitive capacity and feelings about school, as well as the dimension social relation with peers and friends. These results are in line with those reported by Gustafsson et al. , who report associations between daytime sleepiness and HRQoL, including school-related sub-score measured by the Pediatric Quality of Life Inventory, in 10–15-year-old Finnish school children. Several other studies have revealed the association between sleep and impaired school performance, academic achievement, attention, and learning motivation [30,31]. Furthermore, peer victimization, including bullying, has been shown previously to be related to sleep problems [32-34]. The relation between peer victimization and sleep problems is stronger in younger than older children . Being bullied is associated with symptoms of severe mental health problems and can have serious consequences over time [35,36]. Direct questions about victimization or bullying are not included in KIDSCREEN-27, but the quality of the interaction between the child and peers as well as their perceived support are explored. Low scores are interpreted as feeling excluded and not accepted by peers . Knowing that sleep is important to manage school as well as being able to interact with peers and friends, teachers, and school nurses should inquire about both the quality and quantity of the child’s sleep on a routine basis to promote health and well-being in school children, and advice and support should be offered to the children and their parents in following good sleep hygiene principles.
In the present study, only one child out of 10 was reported to have trouble falling asleep at night, and one out of six took longer than 30 minutes to fall asleep. Moreover, we found that the child’s age was associated with sleep problems; the lower the age, the more problems. It has been previously explained that sleep problems, such as nightmares, sleep terrors, and sleep walking, are more common in pre-schoolers compared to school-aged children [37,38]. It is important to acknowledge children’s sleep as well as psychological well-being when meeting the child at regular health visits. Advice about calming bed routines and healthy sleep habits in combination with good sleep hygiene should be provided early to parents to help prevent sleep problems and manage sleep problems when they happen .
This study is one of few studies exploring healthy children’s sleep and its correlation to HRQoL. The study has several strengths, such as a representative sample, even distribution between girls and boys, and validated measurements, and it provides valuable insight into the importance of sleep for psychological well-being, school, and social relations. However, there are some limitations that need to be mentioned. Since we used parent-proxy reports, our findings must be interpreted with caution. Sleep problems could have been underreported because of parental unawareness of their child’s behaviours at night, especially older children. Children’s self-reports have been shown to reveal more sleep disturbances compared to parental reports [39,40]. Moreover, only Swedish-speaking parents were included in the study, which excludes a large part of the population. Another limitation is that the PISI does not have a cut-off for acknowledging symptoms of severe sleep problems. Future research should focus on determining a cut-off score, as presented in the adult version of the Insomnia Severity Index . Furthermore, the validity of subjective measurements is always questionable. A validation of the PISI to an objective assessment tool, such as actigraphy or polysomnography, would be of highest interest.