INTRODUCTION

Quality sleep is essential for physical and mental health, including organic and immune functions, as well as for the well-being and development of children^1-5. Good sleep is extremely important for children’s neurodevelopment, cognitive performance, memory processes and decision-making. It also helps regulate emotions, behavior and stress^5-8. Sleep disorders, on the other hand, can negatively affect these domains, with possible consequences for health, physical functioning, psychosocial development and cognition^4,5,9-12. There is also a consistent evidence base suggesting an association between these problems in childhood and behavioral and mental health alterations, thus representing an important pediatric outcome^4,5,9-12. These disorders are characterized by significant worsening in stressful situations such as those experienced during pandemics as a result of confinement and changes in social support^6-8.

Pre-school children are at a crucial stage of development when it comes to establishing healthy sleep routines¹². In turn, children are at greater risk of sleep and mental health disorders as a result of the rapid changes that take place during development⁵. Children’s sleep is intrinsically regulated by homeostatic and circadian processes¹³, and sleep and wake behaviors into adulthood are mediated by the characteristics of child development^12,14. However, extrinsic factors play an important role in determining sleep/wake patterns and circadian rhythmicity³. Thus, behavioral factors (screen time, physical activity and bedtime routine), the physical environment (exposure to light and noise) and parental factors (stress, upbringing and attachment between parents and children) influence children’s sleep¹³. In addition, timetables, activities and teaching methods are mediators of exposure to sunlight and the use of technology, influencing children’s sleep-wake cycle and sleep duration^3,4.

Overexposure to blue light, through the use of screen-based devices, especially at night, and less exposure to external light, can lead to disturbances in the circadian sleep/wake rhythm and, therefore, sleep, due to the suppression of melatonin and activation of wakefulness systems^5,10,11. Compared to adults, children are more susceptible to the negative effects of exposure to artificial light at night, as melatonin is more sensitive to light at this stage of life¹⁰. In addition, the content consumed by screen devices can make it difficult to fall asleep⁵. On the other hand, physical activity and outdoor play, in particular, can help regulate melatonin secretion and the circadian rhythm, with positive results on sleep¹⁵.

With regard to behavioral factors and parenting practices, it should be noted that pre-school children require more attention and care from their parents, as they have more pronounced separation and attachment problems^16,17. In this sense, sleep disorders can appear as a result of parental stress and anxiety, especially maternal stress^3,18. The stress and sleep disorders have a bidirectional relationship in which non-harmonious, dysfunctional and less positive parental relationships can harm the child’s behavior, well-being and quality of sleep^19,20. High levels of stress and anxiety can be passed on from parents to children, making it impossible to provide a supportive environment for them²¹.

Many of the factors that influence children’s sleep patterns have been significantly affected by the lockdown caused by the coronavirus disease 2019 (COVID-19) pandemic, including limited access to areas for play and recreation, as well as school closures^{2-4,7,8,12,22,23} With the lockdown, children have been exposed to routines, activities and changes in the use of electronic devices that trigger sleep disorders¹². In particular, children’s absence from school, with increased screen time, less physical activity and irregular sleep patterns, can impair circadian rhythms and sleep¹⁰.

As a result of the lockdown, there was less exposure to daylight, changes in daily routines (increased use of electronics with more exposure to blue light, reduced physical activity, limited outdoor activities and reduced leisure time), continuous contact with family, less social interaction, increased family worries, more stress and anxiety for parents, and unrestricted sleep schedules^{2-4,7,8,12,22,23}. In addition, confinement posed a challenge for parents to manage their children’s behaviors¹⁶. Thus, the impact of COVID-19 on the lives of children and their parents can be striking, resulting in a significantly large number of consequences not only on health, but also on children’s social, emotional and mental well-being, including their sleep patterns^2,3,9,23. This impact can be lifelong⁹.

The harmful effects of these changes on children’s sleep have been examined by studies reviewing the world’s literature^24-26. In the first review on the subject, researchers showed a combined prevalence of sleep disorders in children and schoolchildren of 54% and a worsening of sleep quality of 27% during the pandemic²⁴. In children aged 12 and under, the most important changes related to the COVID-19 lockdown on sleep found were longer sleep duration, delays in going to bed and waking up, increased sleep latency, daytime sleepiness and other sleep disorders²⁵. In another systematic review with meta-analysis, the results suggest an influence of the pandemic on sleep characteristics, such as increased sleep duration, late bedtimes and decreased sleep efficiency²⁶. In addition, according to the study, changes in family routines during the pandemic were related to these sleep changes and increased use of screens/electronic devices was associated with poorer sleep quality²⁶. Thus, studies are needed to better understand the effects of social distancing and school closures on children’s sleep during the COVID-19 pandemic^24-26.

Thus, the aim is to assess the sleep habits of pre-school children when they return to school after the COVID-19 lockdown in Brazil. A better understanding of the effects of the pandemic on children’s sleep can help to take the necessary measures aimed at changing behavior, and educating parents and health professionals, in order to avoid short- and long-term consequences.

METHODS

RESULTS

The results of the study are shown in Table 1. Of all the children in the study, the most prevalent negative health condition was hospitalization since birth for 24 hours or more (38.9%). The proportion of children with SHN was 26.2% and with a complete pentavalent vaccination schedule was 89.7%. Of the mothers, 19.0% said they found it difficult to look after their child and give them advice on health aspects. With regard to recreational screen time, 86.5% of the children spent more than 60 minutes. Physical activity time of less than 180 minutes was 58.7%. During the COVID-19 pandemic, 82.5% of the children wore a mask in their routine, 78.6% used to sanitize their hands, 63.5% were in social isolation whenever/almost whenever recommended and 72.2% felt worried about the disease.

Hospitalization since birth for 24 hours or more (p = 0.047, p = 0.010, p = 0.000) and the mother’s difficulty in caring for the child and guiding them in health aspects (p = 0.003, p = 0.023, p = 0.037) represented lower averages for both bedtime routine and rhythmicity and affective separation. Children with more than 60 minutes of recreational screen time also had lower bedtime routine averages (p = 0.002). For affective separation, health problems at birth (p = 0.001) and screening for SHN (p = 0.025) also influenced the averages negatively.

For the variables on behavior during the COVID-19 pandemic, children who did not express concern about the disease had better bedtime routine habits (p = 0.003) and rhythmicity (p = 0.027). In addition, children with a mask-wearing routine had a higher average bedtime routine (p = 0.003).

DISCUSSION

The present study provides an analysis of the sleep habits of preschool children on their return to school after prolonged confinement at home during the COVID-19 outbreak. The children’s sleep habits resulted in mean scores of 7.0 ± 3.4 for bedtime routine, 7.3 ± 3.6 for rhythmicity and 12.8 ± 4.1 for affective separation, representing 46.7%, 40.6% and 71.1% of the respective maximum scores. The child’s health conditions (health problems at birth, hospitalization and SHN), the mother’s difficulty in caring for the child, the child’s screen time being longer than recommended, the child not wearing a mask during the COVID-19 pandemic and the child’s worry about COVID-19 negatively influenced one or more of the sleep habits analyzed.

The results of studies suggest an influence of the COVID-19 pandemic on the sleep characteristics of young children, such as increased sleep duration, late bedtimes and impaired sleep quality²⁶. For example, a Spanish study showed a decrease in sleep time in 3 to 4-year-old preschoolers³⁵. In France, researchers found a significant increase in sleep disorders in young children, with an increase in the overall score on the Sleep Disorders Scale for Children, a reduction in the number and duration of naps, and an increase in the duration of night-time sleep³⁶. In Italy, they also found disturbances in young children for sleep variables such as duration, falling asleep, nocturnal awakenings and parasomnias³. In contrast, observations of other realities have shown a deterioration in the routine and quality of sleep during the initial phase of confinement with subsequent stabilization, such as in Italian children aged 3 to 637, in Chilean children aged 1 to 538, and in infants (0-35 months) and preschoolers (36-71 months) from different countries, mainly European ones⁶.

Although the results of this study do not allow us to establish changes in sleep as a result of the lockdown, they indicate poor sleep quality during the pandemic, during the back-to-school period, in line with previous studies^3,6,35-38. In Brazil, a study of adults found that sleep quality worsened during the distancing imposed by the COVID-19 pandemic³⁹. In this sense, it can be conjectured that children’s sleep is affected by the interaction between parents and children, including the reaction to adverse events such as confinement, and is related to the parents’ sleep^18,40.

For the sleep habits of interest in this study, rhythmicity and bedtime routine were the most compromised, which reinforces the findings of previous studies that have highlighted the presence of sleep disorders in children related to confinement^{3,6,7,10,18,36}. Thus, it is possible to point out that the children had problems with the regularity of bedtimes and wake-up times, nocturnal awakenings and dependence on sleep, which are plausible for modification through more positive parental practices related to sleep organization^28-31. Establishing a structured day with set times is an easy and efficient strategy for children to improve their behavior and sleep quality⁴¹. Maintaining a regular sleep schedule and using only the bed for sleeping, together with physical exercise and limited use of media before bedtime, are fundamental solutions for promoting good sleep quality⁴². In addition, the importance of the family context, which should be harmonious and communicative, should be emphasized².

Changes in family routines and behaviors during the COVID-19 pandemic may have influenced children’s sleep characteristics^2,26,41. In addition to isolation, the pandemic has led to the need to include contagion prevention habits in the routine, such as wearing a mask and hand hygiene⁴³, which, as previously observed⁴⁴, were frequent in this study. Good adherence to these measures is based on their preventive nature, functionality and safety⁴⁴. However, these habits are not always understood by children⁴³, in whom, in addition, environmental influences generate more consequences as a result of changes in the development process⁶. These circumstances can lead to unfavorable psychological and emotional outcomes and interfere with sleep^6,40,43,45, showing plausibility for the relationship found in this study between the mask-wearing routine and the bedtime routine. However, in another study, the quality of children’s sleep was not associated with adherence to isolation recommendations or with social interaction⁶.

Negative repercussions on children’s sleep during the pandemic may be related to problems with emotional well-being^{2,37,40,45,46}. In a study carried out in Italy, 72.2% of the parents interviewed said that their children had become more nervous, worried or sad six months after the start of the pandemic, representing a risk factor for sleep disorders such as difficulty falling asleep and staying asleep at night⁷. In Canada, researchers have shown changes in family sleep habits associated with fears and concerns about COVID-19 among both parents and children⁴².

In the present study, the proportion of children worried about the disease was significant and a determinant of bedtime routine and rhythmicity. These results may be related to anxiety, which translates into difficulties in self-regulation at bedtime⁴⁴ and interferes with sleep quality^{2,37,40,45,46}. Fear-mongering media and spending too much time reading news or talking about COVID-19 can exacerbate worry about the disease and anxiety^18,42. Educational tools that stimulate development, such as talking to children about COVID-19, practices such as meditation, yoga and listening to relaxing music/sounds before bed, can alleviate feelings of anxiety and improve sleep⁴¹.

In this study, more recreational screen time than recommended among children was 86.5% and led to lower average bedtime routines (p = 0.002). Other studies have shown that pandemic restrictions have led to reduced physical activity, increased screen exposure and altered sleep patterns among preschoolers^35,38,45. The increase in screen time during the COVID-19 pandemic as a condition associated with sleep disturbances was confirmed by a literature review²⁶, highlighting the need to monitor and reduce children’s use of electronics, which could be replaced by social interaction, especially at bedtime^38,41,45. In addition, access to appropriate spaces for active play at home or in the environment can benefit both 24-hour movement behavior and sleep quality^6,38.

This situation is particularly important among preschoolers, who were the group most affected by restrictions during the pandemic, especially with regard to physical activity and recreational screen time, as they have more access to electronic devices and need more space to play, compared to younger children³⁸. It is important to emphasize that restrictions on movement to contain the transmission of the virus have varied according to the country and other particularities, resulting in differences in children’s physical activity patterns, sedentary behavior and sleep^26,35,38. The strength of this influence can be seen in a study which showed that isolation had an attenuated impact on physical activity levels, screen time and sleep quality when children had access to play spaces³⁸. Another important finding was the difference in screen time and sleep when comparing children in situations of strict and relaxed confinement found by other researchers³⁵.

With regard to maternal care, it was found that the mother’s ease of caring for the child led to fewer problems with bedtime routine, rhythmicity and affective separation, reinforcing previous findings that emphasize the importance of childcare in meeting children’s needs and protecting sleep quality^2,6. In this sense, caregiver characteristics such as knowledge about healthy sleep practices, the adoption of consistent sleep routines, communication with children, time available to provide care and resilience are relevant^2,6,7,18,47. However, the pandemic may have influenced these characteristics and caused damage both to parental behavior and control and to children’s sleep quality^24-26. Improvements in the quality of care provided to children are essential, as positive behaviors and reflexes from parents towards their children, with the appropriate synchrony between them, facilitates the development of emotional self-regulation capacity and sleep regulation in young children, whose natural tendency is to synchronize with their social and family environment, especially mother-child, on both behavioral and physiological levels¹⁸. Adequate parental knowledge and practices related to children’s sleep are essential for recognizing, avoiding and managing sleep problems in the first years of life⁴⁷.

Finally, the children’s health conditions, as evidenced by health problems at birth, hospitalization and screening for SHN, also had a negative influence on their sleep habits. A study carried out in Italy six months after the start of the pandemic with ≤18 year olds including children with disabilities, autism spectrum disorders, chronic illnesses and specific learning difficulties showed related results. In this research, the presence of chronic illnesses was associated with difficulties in maintaining sleep, while difficulty falling asleep was greater in children with multiple conditions⁷. These results can be explained by the relationship between sleep and the stress response system. There is evidence showing a link between circadian rhythm and sleep and physiological adaptations and disturbances such as increases in blood pressure, insulin and glucose⁴⁸. Therefore, providing specific guidance on sleep to support family members of children with health-related vulnerabilities is essential, especially in the adverse conditions of confinement⁶.

The results of this study do not allow causality to be inferred based on its design. They should also be interpreted with caution, as they refer to a specific moment after the COVID-19 lockdown in Brazil. Another limitation of this study is that the measurements were based on mothers’ reports, which may not fully reflect the reality of children’s concerns. However, they provide important results on children’s sleep habits related to the pandemic. There is still little evidence on the effects of the pandemic on children’s sleep obtained through face-to-face surveys and the studies carried out show great heterogeneity in the instruments used, with the findings for pre-school children standing out for being inconsistent^24-26.

CONCLUSION

The averages of children’s sleep habits indicated problems mainly with rhythmicity and bedtime routine. Children with health problems, excessive screen time and concern about COVID-19 during the pandemic, as well as the difficulty of maternal care, influenced the children’s sleep habits.