Sleep initiation patterns and sleep quality among toddlers in the southeast of China: initial study results

Infancy is the fastest growing period of physical and psychological development in a person’s life, good sleep may have an important impact on the physical growth, psychological and behavioral development of infants. The growth in length of toddlers is associated with extended sleep and increased naps [6]. The sleep routines of toddlers and their parents were disturbed during the COVID-19 pandemic, especially COVID-19-related lockdowns. Interestingly, diverse alterations in sleep patterns among pediatric populations in different countries have been observed during the COVID-19 pandemic, as highlighted in pertinent literature, and there is no consistent expectation of worsening sleep patterns. In comparison to the 2018 sample, preschoolers (aged 4–6 years) in Southwest China exhibited altered sleep patterns before the COVID-19 outbreak, including later wake times and bedtimes, shorter nap durations, extended nocturnal sleep, and reduced sleep disturbances [7]. Research carried out during the complete lockdown in Italy, focusing on children aged 2–5 years, indicated noticeable delays in both wake-up and bedtime routines. Nevertheless, the proportion of children with some sleep difficulties (i.e., SDSC > 39) remained constant, increasing from 41.46% before the lockdown to 44.72% during the lockdown [14]. An Israel research explored the possible negative implications of the COVID-19 pandemic on sleep for both children aged 6 to 72 months and their mothers. However, data showed that approximately 30% of mothers reported a decrease in the children’s sleep duration and quality, and also mothers reported positive changes [15]. A meta-analysis encompassing children and adolescents from diverse Asian countries, South America, and European countries demonstrated that at least 21.3% of children experienced sleep disturbances during COVID-19 pandemic [16]. As reported in the research by Cassanello et al. [8], longer sleep latencies (> 30 min) ware observed in more infants and toddlers (with a median of 33.9% versus 12.3%). Before and under the COVID-19 outbreak lockdown, the proportions of children whose sleep perceived as problematics were 39.4% and 44.1%. This study identified that feeding to sleep and cuddling to sleep significantly reduced the length of nighttime sleep among the toddlers during the pandemic of COVID-19. In our study, 331(67.1%) initiated sleep accompanied by parents, 67(13.6%) slept independently, 59(12.0%) were breast fed/bottle fed to initiate sleep, 27(5.5%) were held and 9 (1.8%) rocked during COVID-19 pandemic. Thus, although the proportion of infants and children of different ages who fall asleep poorly varies in different places, poor sleep patterns are still widespread.

Poor sleep pattern is defined as the inability to fall asleep alone and relying on behaviors such as nursing, patting and rocking that are not for feeding purposes. The present study showed that different sleep-initiated patterns influenced the length of night sleep and the number of night awakenings of toddlers, among who were fed, rocked, and held to sleep were significantly more frequent than those who fell asleep on their own. Regular nighttime breast feeding, excessive viewing, or lack of general knowledge about child sleep hygiene (e.g., mistaking vocalizations, sport activities, and facial expressions that occur in the baby’s light sleep state as signs that the baby is awake and picking the baby up) may artificially increase the number of infants and toddlers waking up at night [17]. Additionally, sleep initiation with bottle feeding/breast feeding, rocked and cuddled may all exhibit certain poor bedtime soothing behaviors, which interfere with the normal development of young children’ sleep rhythms, resulting in longer sleep latency, more nighttime awakenings, and poorer sleep [8, 18]. A multi-center cross-sectional survey on the dose-dependent relationship between sleep outcomes and bedtime routines in infants and young children from mainland China indicated that 48.5% (632/1304) children had not established regular sleep routines reported by the parents. The more regular sleep routines were associated with earlier bedtime, fewer night awakenings, shorter sleep onset latency and duration of nighttime waking, and longer the sleep duration. For example, people who had a bedtime routine “every night” had significantly longer nighttime sleep than those who “never” had a bedtime routine[9.5(95%CI: 9.4–9.6) vs 0.8.9(95%CI: 8.6–9.3), t = 3.345, p = 0.001] [19]. Sleep initiation patterns in young children were associated with extended use of electronic devices, and young children who are exposed to electronic screens every day have a higher probability of being breast fed/bottle fed to sleep [20]. The fact that screen time viewing replaces other sleep-friendly activities [21], such as parent-child interactions or exercise duration, and excessive screen time can trigger sleep problems [22]. It is estimated that for every hour of screen use, sleep is delayed by 5–10 min [21]. For this of reason, the American Academy of Pediatrics recommends not using them at least 1 h before bedtime [23]. Our findings show that a higher probability of needing to be rocked to sleep at bedtime in toddlers exposed to electronic screens on a daily basis, which is hypothesized to be related to an increase in sleep latency, where bright light may lead to cognitive and emotional activation [24], producing a state of heightened arousal [25], reducing melatonin production [26], and a delay in sleep latency and the need for alternative ways to help falling asleep. During the COVID-19 pandemic, limited outdoor activities, lack of interaction with children of the same age, and excessive electronic screens may result in delayed sleep, more sleep problems, and decreased sleep quality compared to weekends and holidays. These may further have a negative impact on physical and mental health, and therefore it requires attention and intervention.

Frequent nocturnal awakening is as one of the manifestations of circadian rhythm disturbance. The incidence of problematic nocturnal awakenings is higher in our infants and young children compared to overseas children of the same age [17]. In the current study, the 1–2, and 2–3 rates of toddlers waking up more than once a night was 64.6% and 67.2%, respectively. In addition, parental bedtime habits and toddlers’ sleep patterns are intricately linked, displaying a high degree of chronicity in sleep problems that are influenced by previous sleep behaviors and sleep arrangements. Clinically, when parents are counseled about co-sleeping their infants, the quality of the mother’s sleep should be taken into account. A cross-sectional survey conducted in 2019 (before the outbreak of COVID-19) from six provinces in China indicated that the bed-sharing practice ranged from 69.9 to 78.3%, which was very prevalent at any age. Most young children before age 12 months fell asleep while being rocked/held or feeding. By 35 months of age, 62.4% of children slept in the bed alongside their parents. The most popular explanation for bed-sharing were breast-feeding/bottle-feeding, and difficulty falling asleep and frequent night awakenings among the children were significantly impacted by parental involvement [27]. Good sleep quality is associated with more regular sleep routines [19].

Despite the fact that bed-sharing and parental involvement are still widely practiced among young children in China, on the contrary, our study found young children falling asleep along with parents have less nighttime awakenings during the COVID-19 pandemic. Nor was there an association between sleep and bed-sharing. Bed-sharing remained an independent and graded predictor of nocturnal awakenings and shortened sleep duration, even after controlling for preceding sleep conditions [28]. Irregular and later parental bedtime routines worsted infants and toddlers sleep [29]. Nonetheless, an important finding revealed that children under 36 months of age in Hong Kong who were able to fall asleep independently exhibited fewer instances of sleep awakenings and enjoyed longer nocturnal sleep duration, whereas sleep location did not show the same association. This is especially important for families with restricted living space who cannot avoid parents/children sharing beds or rooms [29]. At present, the proportion of regular sleep patterns among young children in mainland China is still low, and breastfed children mostly rely on breast fed/bottle fed to initiate sleep, while most older toddlers fall asleep mainly in the company of their parents. Further research is required to discern the potential advantages of how bed-sharing interacts with infant care practices beyond sleep [20]. Furthermore, the negative impact of insufficient and inadequate sleep on children’s physical and mental health are indisputable, as are the effects on cognitive functions, academic achievement and performance, all of which are higher risk factors for children in low- and middle-income countries. Behavioral interventions for mothers and young children that are inexpensive and do not require specialized training can reduce the risks faced by these children and thus help prevent future problems [30].

A limitation that is the use of single assessments of sleep in young children, including parent-reported sleep questionnaires. Indeed, multiple assessments of sleep in young children, including parent-reported sleep diaries and actigraphy-based assessments should be considered. Given the sample size, this is a cross-sectional observation of 12- to 35-month-old children in Fujian Province only. And a larger sample size including more ethnic/racial groups are needed in more studies, especially longitudinal studies. There are, however, the causal relationship between sleep quality and sleeping patterns (bedtime, sleep duration), sleep behaviors still need to be assessed by further research. However, it is important to note that there may be some differences in sleep patterns between the during and after COVID-19 pandemic. While our study provides valuable insights into the potential impact of the COVID-19 pandemic on children’s sleep, further research is needed to follow up the sleep of children during and after the COVID-19 pandemic in the following study for comparison.