Sleep problems and infant motor and cognitive development across the first two years of life: The Beijing Longitudinal Study

https://doi.org/10.1016/j.infbeh.2021.101686Get rights and content

Highlights

  • High scores on the Bayley infant development assessment at 6 months predicted less nocturnal awakenings at 1 year of age.

  • Insufficient nocturnal sleep at 1 year predicted poor fine motor development at 2 years.

  • Sleep patterns of Beijing infants were somewhat different from those of their Finnish counterparts.

  • Infant development predicts later sleep problems, but sleep problems can also predict subsequent development.

Abstract

The present study examined bidirectional effects between sleep problems (nocturnal awakenings and insufficient nocturnal sleep) and infant development (gross motor, fine motor, and cognition) in a sample of 182 infants (89 girls) and their parents living in Beijing (China). Using 3 waves of longitudinal data (at 6 months, 1 year, and 2 years of age), this study (a) explored the differences in sleep patterns and developmental outcomes between infants in the current sample and infants from other cultures; and primarily examined (b) whether nocturnal awakenings and insufficient nocturnal sleep prospectively predicted infant development; (c) or whether infant development predicted sleep problems. Mothers reported their children’s sleep problems, and infant development was assessed with Bayley III. Sleep patterns of Beijing infants were slightly different from those from Finland and Singapore, and most scores on Bayley III in this Beijing sample were higher than those in Danish, Dutch and Sri Lankan samples. Sleep problems and developmental measures were stable across the 3 times of assessments, but cross-lagged associations were limited in number and strength. High scores on the Bayley at 6 months predicted less nocturnal awakenings at 1 year of age. Insufficient nocturnal sleep at 1 year predicted poor fine motor development at 2 years. Thus, findings suggest some bidirectional associations between infant development and sleep problems and further highlight the need to understand these relations within specific cultural contexts.

Introduction

Sleep problems during early childhood seem to be universal (Jiang et al., 2007, Paavonen et al., 2020, Owens, 2008). Although there is no consensus on how to define infant sleep problems, anything that disturbs the parents or does not match parents’ expectations about sleep may be considered problematic (Barry, 2021). Super & Harkness (2013) proposed that the development of sleep is not only a biologically based universal behavior, but it is also regulated by social and cultural environments. Most studies on infant sleep problems include Western children from WEIRD countries (Western, Educated, Industrialized, Rich, and Democratic societies; Henrich, Heine, & Norenzayan, 2010), however large differences may, for example, exist in co-sleeping patterns which is not only a traditional custom but still popular in large parts of the world. As suggested by Barry (2021), more work therefore needs to be done on infants experiencing co-sleeping. In China, young children seem more likely to share a room or bed with caregivers than those from Western countries (Mindell, Sadeh, Wiegand, How & Goh, 2010), and a recent systematic review suggested that non-WEIRD countries have higher reported bed-sharing prevalence than WEIRD countries (Mileva-Seitz, Bakermans-Kranenburg, Battaini & Luijk, 2017). In the debate on the roles of sleep problems in children’s development one of the questions is whether they are causes or outcomes (or both) of infant’s motor and cognitive development. This question is addressed in our longitudinal study on families with infants in a non-WEIRD culture.

Frequent and persistent nocturnal awakenings are one of the major concerns of parents when evaluating their children’s sleep quality (Palmstierna et al., 2008, Yu et al., 2017). Insufficient sleep duration is another type of sleep problem that is prevalent among Chinese children beyond infancy (Gong et al., 2018, Takahashi et al., 2018, Wang et al., 2013). According to the recommendation of the National Sleep Foundation (2015), the average total sleep duration of more than 12 h by Chinese infants and toddlers in the study of Mindell et al. (2010) is appropriate. However, young Chinese children went to bed later, and their sleep duration at night was 30 min to 1 h shorter than that of their Western counterparts (Mindell et al., 2010). Since more frequent and longer daytime naps have been found in Chinese infants and toddlers (Lin et al., 2019), their shorter nocturnal sleep might be compensated by longer naps during the day. The facilitating role of daytime sleep on young children’s motor learning and cognitive performance has been examined with respect to specific abilities and sleep states in a number of experimental studies (Jones & Spencer, 2020). In addition, it is often embedded in a cultural belief that there are academic benefits to daytime napping in China. Thus, whether the prolonged daytime sleep duration is one of the indicators of sleep problems remains an open question in the current study.

Developmental cascade theory emphasizes the cumulation of early sleep problems over time that may feed forward or cascade into other developmental domains such as the motor or cognitive domain (Camerota et al., 2019, Masten and Cicchetti, 2010). Previous studies on relations between sleep problems and infant development (assessed by the Ages & Stages Questionnaire or the Bayley Scales), however, showed inconsistent results. Some studies found that sleep duration and awakenings had no relation to any kind of motor ability (Mäkelä et al., 2018, Mindell and Lee, 2015) or cognitive performance (Camerota et al., 2019, Mäkelä et al., 2018, Pennestri et al., 2018, Spruyt et al., 2008). However, other studies found that less fragmented sleep and higher sleep efficiency of infants and toddlers were associated with better performance on the mental scale of the Bayley I (Sun et al., 2018) and Bayley II (Scher, 2005). Moreover, nocturnal wakefulness at 3 months could predict later poor gross motor and cognitive development (Dearing et al., 2001, Tham et al., 2015).

Using a dynamic system view Scher and her colleagues found that new gross motor capacities may account for the periodic rise in parents’ reports of night awakenings (Atun-Einy and Scher, 2016, Scher and Cohen, 2015). In addition, Dias & Figueiredo (2019) proposed reversed causality in that lower scores on cognitive development may be associated with worse sleep-wake patterns. Because a limited number of longitudinal studies have focused on how motor or cognitive development affect children’s sleep, important questions regarding the directionality, timing, and magnitude of the association between sleep problems and cognitive and motor development have remained unanswered (Staples & Bates, 2013). As most previous studies focusing on early childhood included only one or two time points, we followed the suggestion by Smithson et al. (2018), to assess both infant sleep and development three times from six months to two years, which allows us to estimate bidirectional associations between sleep problems and infant development.

In two Chinese infant samples, the prevalence of sleep problems reported by parents ranged from 65.97% (Jiang et al., 2007) to 75.93% (Mindell et al., 2010), which was higher than the prevalence reported by Western parents. It is suggested that Chinese parents may differ from their Western counterparts on their perception of their children. Sadeh, Mindell, & Rivera (2011) found that in Western countries reported sleep measures could predict the parental perception of sleep problems. In contrast, demographic variables (age of the child and parent, and parental education level) were more strongly related to parental definitions of the sleep problems in Asian countries. Thus, we examined whether the prevalence of sleep problems reported by highly educated mothers in our sample is still as high as that reported nearly a decade ago. We also compared sleep patterns in the current sample to two similar studies conducted in Finland (Paavonen et al., 2020) and Singapore (Tham et al., 2021).

Chinese parents also differ from Western parents in the kind of parenting they provide (Muthukrishna et al., 2020). Children’s educational achievement is likely to be an important value for Chinese parents, given the accumulating evidence suggesting that children’s education since infancy has become a family project of major investment and management of parents, especially in urban settings (Gu, 2021). A recent survey revealed that 52.7% of the interviewed parents let their children under 5 participate in some courses or activities of early education institutions (Wang, 2016). Cross-cultural studies also indicated that parents may influence their infants’ motor actions (Adolph, Karasik, & Tamis-LeMonda, 2010) and cognition-related activities (Ng, Pomerantz, & Lam, 2007) by specific parenting practices in different cultures. Thus, we first characterized and compared these developmental outcomes in the current sample and four comparable samples from Denmark (Krogh & Væver, 2018), the Netherlands (Steenis, Verhoeven, Hessen & van Baar, 2015), the United States (Bayley, 2006b), and Sri Lanka (Godamunne et al., 2014). Although these comparisons cannot explain the potential differences between these cultures, they may provide culturally relevant background for our findings.

Based on prior research, we propose three main hypotheses. First, we expected significant differences on sleep patterns between the infants with and without sleep problems in this sample; that is, infants with sleep problems would experience more and longer night awakening, spend more time on falling asleep and daytime sleep, and have a shorter nocturnal sleep duration than infants without sleep problems. In addition, we assumed that the rank order of individuals would remain stable over time for sleep problems, but on average sleep problems would decrease over time.

Second, in terms of the commonalities and specificities of sleep patterns, motor and cognitive development, we expected that there would be significant differences in the sleep patterns and other developmental outcomes between infants from Beijing and infants from Western cultures (i.e. Finland: sleep patterns; Denmark, the Netherlands, and the United States: motor and cognitive outcomes, but that there are few differences in the developmental outcomes between Beijing infants and other Asian infants (i.e. Singapore: sleep patterns; Sri Lanka: motor and cognitive outcomes).

Finally, inspired by the developmental cascade theory (Masten & Cicchetti, 2010), we proposed that more sleep problems would predict lower levels of concurrent and later motor and cognitive development. To acknowledge the potentially bidirectional nature of early development in different developmental domains, we proposed that lower levels of infant motor and cognitive development would also predict more sleep problems later in infancy.

Section snippets

Procedure

We recruited participants and collected data between June 2015 and May 2018. Laboratory visits were conducted when infants were 6 months old (T1), 1 year old (T2), and 2 years old (T3). At each time point, primary caregivers completed questionnaire measures pertaining to demographics, income, and educational background of the parents, as well as infants’ sleep before they visited our laboratory. During each laboratory visit, infants were administered the motor and cognitive development

Preliminary analysis

Little’s test of missing completely at random (MCAR test; Little, 1988) was used to determine whether the data were missing completely at random. The result was not significant, χ2 (1151) = 1211.07, p = .11, suggesting that the MCAR assumption was tenable. To reduce the likelihood of selection bias, selected covariates were used as control variables in the analyses. Infants’ gender and family socioeconomic status (SES) were important covariates to account for sleep problems and developmental

Discussion

The present study examined longitudinal associations between sleep problems (insufficient nocturnal sleep and nocturnal awakening) and infant development (fine and gross motor development and cognitive development) during infancy. Sleep problems persisted across the first two years of life, and across the same period, individual differences in motor and cognitive development were relatively stable. Importantly, we found evidence that lower levels of fine motor and cognitive development at 6

CRediT authorship contribution statement

X.L. performed the statistical analysis, interpreted the results and drafted the manuscript. X.Z. and Y.W. collected and prepared the data. Z.W. designed the study. M. V. IJ. advised on the statistical analyses and helped to revise the full manuscript. All authors read and approved the final manuscript.

Conflict of Interest

This was not an industry-supported study. The National Natural Science of China did not have any influence on the study design or report. None of the authors has any financial conflict of interest.

Acknowledgements

We would like to thank all the families and research assistants who have participated in the Beijing Longitudinal Study 2015. We acknowledge Dr. Marianne T. Krogh and colleagues for sharing the data from their Danish sample. The project was funded by the National Natural Science of China, China, Grant/Award Number: 31700967, 31971006; General Project of Science and Technology Plan of Beijing Municipal Education Commission, China, Grant/Award Numbers: KM20201002820, KM201910028003.

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