This longitudinal study aimed to investigate the effects of the COVID-19 pandemic on preschool-aged children’s PA, screen time, sleep, and mental health using subjective and objective measures.
Our results demonstrated that compared to the pre-COVID-19 period, weekday MVPA, weekday light PA (LPA), and weekend LPA decreased, whereas weekday and weekend SB increased as measured using an accelerometer during the COVID-19 pandemic. Our results on PA were consistent with the results of a Spanish study 32 and a Chilean study 33 on preschool-aged children, as well as with the results of Tunisian 34, Chinese 8, Canadian 9, US 10, and German 35 studies on school-aged children between 5 and 17 years of age with different restrictions such as lockdowns. In particular, one notable finding of this study is that LPA and MVPA were affected by COVID-19 and that the levels during weekends and weekdays decreased.
Children generally engage in PA, as they participate in organized play, games, and dance in institutions (childcare, kindergarten, and elementary school) and spend time in the playground and park after school 36. However, the transition to online learning and social restrictions brought on by the COVID-19 pandemic hindered preschool-aged children’s participation in school-based or community-based PA through physical education, sports, or other activities. Our results demonstrate that weekday MVPA decreased after the COVID-19 outbreak, which suggests that social restrictions also contributed to reduced organized PA among children in childcare centers (wearing a face mask during exercise, bans on group play, and restricted play areas). It has been reported that children and adolescents are spending less time outdoors during the COVID-19 pandemic 9,10. Reduced outdoor playtime may have a substantial impact on reduced MVPA and LPA among children. A systematic review reported that the guidelines for maintaining an active lifestyle during the COVID-19 pandemic published by many international organizations have little consideration of vulnerable groups (older adults and young children) and that even during this period, individuals need to engage in periodic PA to maintain good mental and physical health 37. As demonstrated in the present study, outdoor play is crucial to boost PA during the COVID-19 pandemic, and policies that enable children to play outdoors with minimal infection risk (use of a face mask and physical distancing in playgrounds, parks, and other green areas) should be devised to address this issue. Both weekday and weekend SB, objectively measured using an accelerometer, increased during the COVID-19 pandemic. Our results are consistent with a previous Spanish study on preschool-aged children, reporting that PA decreased and SB increased 32. The WHO 24-h MG suggests that PA, SB, and sleep are mutually influential through physiological interactions throughout 24 hours. Further, the time spent on one activity may affect another activity. Therefore, each activity should not be treated independently 7.
Next, we compared the rate of adherence to the screen time recommendation of the WHO 24-h MG before and during the COVID-19 pandemic, and the rate significantly decreased from 27.2% before the pandemic to 19.9% after the pandemic. This is markedly low even when compared to Asian countries with similar cultures, such as Japan 21, China 38, and Singapore 39, before the pandemic. After the COVID-19 outbreak, social distancing measures and parents’ self-implemented restrictions on their children due to the risk of infection led to dramatically less outdoor time and increased screen time at home. Previous studies also reported that screen times have significantly increased since the implementation of COVID-19-related quarantine measures 8,36,40. Screen time is an integral social phenomenon in modern society, as screen-based online learning enhances children’s self-esteem, social skills, and knowledge 41. However, the focus should be on reducing screen time on activities, which may have an adverse impact on recreational time, such as playing games and watching TV. Adherence to screen time recommendations is reported to be more strongly associated with family factors, such as parents’ screen time modeling, parents’ TV watching, and house rules, as opposed to individual factors or social factors 42. Hence, subsequent intervention studies should consider parents’ behaviors and support.
Our results also demonstrate that restricted social activities due to COVID-19 had a considerably negative impact on preschool-aged children’s mental health. These results were consistent with findings from other countries, where administrative measures such as lockdowns imposed due to COVID-19 had adverse impacts 43–45. Further, a study on Japanese elementary school students reported that externalizing problems, such as hyperactivity and inattention, increased 46. Our results were also in line with the results of population-based studies conducted before the COVID-19 pandemic, where boys demonstrated more hyperactivity and inattention than girls (boys: 3.2, girls: 2.5) 47. Of the various mental health problems affecting preschool-aged children, externalizing problems (hyperactivity and inattention) are reported to be associated with individual, family, and social factors 48. Hence, it is possible that COVID-19-triggered anxiety and depression among parents may have contributed to children’s externalizing problems 49. Because the social restrictions imposed in response to the COVID-19 pandemic have led to more family time, during which families build stronger relationships with one another, children with hyperactivity and inattention would face a high level of family conflict. The low level of prosocial behaviors, such as cooperativity and empathy, may also be attributable to fewer opportunities to interact with other people outside the childcare center due to the COVID-19 pandemic. Parents, childcare teachers, educators, and administrators must take action to reduce the mental health repercussions of COVID-19 in preschool-aged children. To prepare ourselves for a potential second wave of COVID-19 or the post-COVID-19 era, programs promoting mental health and prevention tailored toward young children in need of care must be developed.
Some limitations need to be considered in the interpretation of the findings of this study. First, since this study was targeted at preschool children in the northeastern region of Japan, it is not clear whether it can be generalized nationally to preschool children in Japan. Second, the study employed a questionnaire survey in which the parents or family members of the child observed the child’s screen time and sleep duration and filled out the questionnaire, as in other studies with preschool children. Third, as parents’ psychological condition has been reported to influence their evaluation of their children’s behaviors 50, mental health and emotional symptoms are likely to be underestimated; these factors should be considered when interpreting the results 51.