This study investigated subjective health complaints and adherence to 24-hour movement recommendations among school-aged children during COVID-19-related school closures and one year after school reopening. Our results indicate that during school closure, children were more inclined to meet only sleep recommendations. However, upon school reopening, a higher proportion failed to meet any recommendation, meeting only screen time recommendations, or meeting both screen time and sleep recommendations. These findings were consistent, irrespective of sex. Additionally, children were prone to experiencing symptoms of irritability and lethargy during school closures. Multiple logistic regression analyses revealed that individuals adhering to two or all three recommendations, excluding physical activity and screen time, had a lower risk of symptoms related to physical and mental pain, fatigue, irritability, and lethargy compared to those who met no recommendation.
It is widely acknowledged that a reduction in physical activity [3–5], an increase in sedentary behaviour (including recreational screen time) [3–6], and an increase in sleep duration [5–7] occurred during pandemic-associated restrictions. Previous studies employing 24-hour movement behaviour guidelines have also indicated that the prevalence of meeting these recommendations presented consistent changes from before to during the pandemic [43–46]. In this study, individuals who met only screen time or sleep recommendations exhibited patterns in line with those of previous studies [43–46]; however, a consistent trend in physical activity was exclusively observed among girls. A survey conducted in Tunisia reported that physical activity decreased during the pandemic among school-aged children, with a decrease of 7% in boys and 17% in girls [47]. However, other studies present contrary results, indicating that the decrease in physical activity is smaller in girls than in boys [48, 49]. Our results, showing a greater proportion of girls meeting the physical activity recommendation one year after school reopening, could support the former report and suggest that the negative impact of school closures due to the pandemic on children’s physical activity was more evident in girls than in boys.
In addition, the impact of the pandemic-associated restrictions on children’s movement behaviours, especially physical activity, seemingly persisted in the aftermath. This was suggested by a Spanish study indicating that adherence to the 24-hour movement behaviour guidelines in children was significantly lower after the pandemic than before it [50].
We hypothesised that attending school would have a positive role in children’s daily movement behaviours; nevertheless, our results revealed an increase in the number of individuals who did not meet any of these recommendations one year after the school reopened. One possible explanation for this outcome could be the increase in individuals who could not meet even the sleep recommendations after schools reopen. Short sleep duration among Japanese children remains a major concern [51]. This issue is so serious that the United Nations Committee on the Rights of the Child has recommended strengthening efforts to ensure every child’s right to sufficient rest and leisure [52]. Our results could reflect that since the schools reopened, the numerous activities that the children are involved in contribute to their short sleep durations. Indeed, a previous study in Japan observed a lack of free time among school-aged children [53], which could explain why they were unable to get sufficient sleep.
Several reports have suggested that there is a high risk of poor concentration, inattention, and irritability in children during the pandemic [54–56]. This finding is consistent with the current results. Further, South Korean and Canadian surveys have indicated that children’s loneliness due to limited social interaction or social isolation during the pandemic impacted their mental health, including depression, irritability, and attention issues [57, 58]. Taken together, the increase in irritability and lethargy observed in this study could be associated with a reduction in social interactions due to school closures. Since social interactions play an important role in children’s psychological development [59], attention should be paid to the current and future mental health of children experiencing extreme social isolation.
Girls were more likely to feel like crying during school closure and experience nausea and headaches one year after school reopening. Academic pressure has a stronger effect on psychosomatic symptoms in girls than in boys [60, 61]. Additionally, school closures contribute to reducing academic pressure on children [62–64]. Thus, our finding of an increase in subjective health complaints, such as nausea or headaches, after the school reopening in girls could be explained by school-related stress.
One key finding is that adhering to two movement behaviour guidelines, particularly combining screen time and sleep or physical activity and sleep, along with meeting all three guidelines, reduces the risk of subjective health complaints among school-aged children. This aligns with previous research suggesting that meeting multiple recommendations improves mental health outcomes in children and adolescents, including depression [29, 32–34], anxiety [29, 32–34], quality of life [35], self-rated physical and mental health [36], and internalising and externalising behaviours [30]. Essentially, meeting at least two recommendations, including sleep, is essential for decreasing the risk of subjective health complaints. This is a remarkable result for Japanese children, as the proportion of children who do not get enough sleep is the highest in the world. Several reports have suggested that sufficient sleep has a stronger impact on children’s mental health than physical activity or sedentary behaviour [33, 65]. These reports and our findings highlight the significance of adhering to sleep recommendations and imply that ensuring sufficient sleep should be a priority for better mental health among school-aged children. If they cannot meet all three recommendations, meeting an additional recommendation in addition to the sleep recommendation could be effective in preventing mental health issues. Strategies that consider the priority of each movement behaviour are necessary, even in abnormal situations, such as social restrictions due to the pandemic.
However, meeting sleep recommendations alone did not significantly reduce the risk of subjective health complaints in this study. One reason for this discrepancy could be that sleep timing was not considered. A later timing of sleep is associated with more headaches, stomach-aches, and backaches among school-aged children in Canada [66]. Not only this study but also other studies have suggested an association between the timing of sleep and mental health among children [67, 68]. Sleep patterns could have substantially differed between the two periods: during school closure and one year after school reopening. Studies on children’s sleep patterns during lockdowns and school closures indicate a tendency for many children to go to bed and wake up later [7, 69]. Taken together, adherence to the 24-hour movement behaviour guidelines is a useful indicator for promoting healthy movement behaviours to improve mental health among children from a public health perspective. However, it is essential to accumulate more evidence to explore the association between combinations of movement behaviours and subjective health complaints. This analysis may need to consider the timing at which each recommendation was achieved.
Previous studies have revealed the prevalence of subjective health complaints in girls [19, 21, 22, 70] and older children [19, 21, 22]. This study examined the differences in sex and age only for fatigue-related symptoms. Additionally, girls were at a lower risk of experiencing these symptoms than boys, which is inconsistent with prior findings [19, 21, 22]. One reason for this difference could be the dissimilar grade ranges of participants. Participants included all elementary school grades. Tanaka and colleagues reported that the scores of subjective fatigue symptoms among boys were higher than those among girls in the third and fourth grades in Japan [71]. Therefore, sex differences could exhibit opposite trends with age. Moreover, a Japanese study on subjective fatigue symptoms revealed that scores for fatigue symptoms were significantly greater in the fifth and sixth grades than in the third and fourth grades [71]. Our results are consistent with this finding and suggest the necessity of a preventive approach for subjective health complaints, particularly those with fatigue symptoms, in the population before early adolescence.
Strengths and limitations
To our knowledge, this study is the first analysis of subjective health complaints among school-aged children during school closures due to the pandemic and one year after schools reopened. While investigations into other mental health outcomes during school closures and surrounding periods exist, they primarily focused on depression and anxiety. This study yields key findings, offering insights into children’s mental health concerns during unprecedented and massive disasters or crises, such as the COVID-19 pandemic.
However, this study had some limitations. First, it employed a cross-sectional design, and participants were recruited using snowball sampling. While participants in this study were drawn from the same schools in both surveys, this was insufficient to completely exclude bias and establish cause-and-effect relationships. We fortunately obtained data twice: in an irregular situation, during school closure, and one year after school reopening. However, future studies on changes in both movement behaviours and subjective health complaints in specific circumstances and settings should include longitudinal data to provide stronger evidence. Second, the data on movement behaviours among the children were self-reported. For a comprehensive observation of movement behaviours and a thorough examination of the genuine relationship between combinations of movement behaviours and subjective health complaints, it is essential to conduct further examinations using accelerometers. Third, this study included a limited number of confounding factors: sex and grade. Sex and gender differences are key factors influencing subjective health complaints [22, 70]. However, further analysis is required to assess various factors and determine what factors potentially affect subjective health complaints among school-aged children. For instance, socioeconomic status is associated with mental health outcomes among children and adolescents [72].