Recent international research has shown that sleep patterns and problems during early childhood can vary substantially according to culture and context (123). Although maturational processes related to establishing sleep/wake cycles during infancy and toddlerhood are partially biologically- and physiologically-determined, psychosocial factors, including parenting behaviors and aspects of the child’s sleep ecology, also influence the development of sleep patterns (45). Importantly, psychosocial factors can contribute to both the etiology and maintenance of early childhood sleep problems (25678), which, if untreated, have deleterious effects on subsequent physical and mental health during childhood (9101112). Examining cross-cultural differences in sleep patterns, sleep ecology, and parenting behaviors can provide important information for parents, health providers, and researchers in conceptualizing and effectively addressing sleep problems in infancy and toddlerhood (12). For instance, comparisons between young children’s sleep habits in predominately Asian versus predominately Caucasian countries/regions revealed that children from predominately Asian contexts had significantly later bedtimes, shorter sleep duration, and increased room-sharing and parental perceptions of sleep problems (2). However, parental presence and behaviors at bedtime were found to be more strongly predictive of problematic sleep outcomes among children in predominately Caucasian regions (1).

Broad cross-cultural comparisons, such as those between predominately Asian and predominately Caucasian countries/regions, should be supplemented with additional country-specific comparisons given that child sleep patterns and problems may vary both within and across different cultures and contexts. For example, a study that examined young children’s sleep patterns in Hong Kong showed that these children had later bedtimes and less total sleep duration compared to children in predominately Caucasian contexts and to children in predominately Asian contexts (9). Falling asleep independently was associated with longer nocturnal sleep duration and fewer nocturnal wakings. Such information is useful for parents and physicians in Hong Kong who are treating common early childhood sleep problems such as frequent night wakings, particularly given that children in Asian regions tend to room-share and are less likely to fall asleep independently (12). Similarly, a study examining infant and toddler sleep in Australia and New Zealand found country-specific differences that have implications for understanding sleep patterns and treating sleep problems in these countries and in comparable contexts (3). Parents in Australia and New Zealand were more likely to encourage young children to self-soothe and to fall asleep independently; these positive parenting practices likely contributed to the longer sleep duration and fewer night wakings found among children in these countries (3). Context-specific studies have also provided normative data on infant and toddler sleep by age (3), which increases within-country/region knowledge of maturational sleep patterns and informs future context-specific research on sleep problems and related interventions.

Few studies have focused on infant and toddler sleep patterns in Korea. One study of 160 Korean infants (birth to 6 months) found decreased sleep duration and increased maternal contact with increasing infant age, although this trend was non-significant (13). A more recent study utilizing the Nursing Child Assessment Sleep/Activity Record in a sample of Korean infants ages birth to 6 months (n = 94), provided limited data on average sleep duration, night wakings, and maternal behaviors regarding infant sleep (14). Unfortunately, these and other studies of sleep among young children in Korea have included small samples that are limited in child age and have used a variety of different sleep assessment tools, making it difficult to generalize normative sleep patterns of infants and toddlers in Korea and to compare study findings across samples (1516).

Accordingly, the purpose of this study was to examine sleep patterns in a large sample of 1,036 Korean infants and toddlers, in order to establish maturational norms on early sleep patterns and problems in this context. We also compared sleep patterns, sleep problems, sleep ecology, and parental behaviors at bedtime among children in Korea to global data from infants and toddlers in both predominately Asian and predominately Caucasian regions/countries, as a method to inform the treatment of early childhood sleep difficulties in Korea. We additionally examined parent and child demographic information, parental behaviors, and aspects of the sleep ecology as predictors of sleep patterns among infants and toddlers in Korea.

The purpose of this study was to examine sleep patterns in a large sample of infants and toddlers (ages birth to 36 months) in Korea, and to compare sleep patterns, sleep problems, sleep ecology, and parental behaviors to global sleep data on young children in both predominately Asian (P-A) and predominately Caucasian (P-C) countries/regions. We also examined demographic and sleep ecology predictors of sleep/wake patterns within the Korean cultural context. To the best of our knowledge, this is the first large-scale study of infant and toddler sleep in Korea. It is our hope that these findings will be used as a reference for future studies of sleep habits among children in Korea.

About the sleep/wake patterns, consistent with other cohort-based studies of sleep in early childhood (181920), infants and toddlers in Korea showed increasingly consolidated sleep patterns with increasing child age. Daytime sleep duration and nocturnal awakenings generally decreased with older child age, whereas nighttime sleep duration and the longest sleep episode both tended to increase. Although it is difficult to directly compare study results to previous work on infant and toddler sleep in Korea due to differences in study measures and samples, findings on increased sleep consolidation with increased child age do align with available research in Korea on this topic. For instance, a previous study of 94 infants in Korea showed that between 0 and 6 months, daytime sleep duration decreased with increased child age (14). Findings from stepwise regressions using child and parent variables to predict sleep outcomes (discussed further below) also support these results, given that older child age significantly predicted decreased night wakings and daytime sleep, increased nocturnal sleep duration, and longer sleep episodes.

Sleep/wake patterns as well as aspects of the sleep ecology and parental perceptions of child sleep problems in the Korea samples differed in comparison to infants and toddlers in P-A and P-C countries/regions. Study findings suggest that infants and toddlers in Korea generally obtain less sleep than their counterparts in both P-A and P-C samples. Specifically, children in Korea had the latest bedtimes, the shortest total sleep time, the shortest daytime sleep duration, and the least number of naps per day compared to both P-A and P-C groups.

On the one hand, shorter total sleep for children in Korea could suggest that these children may be at higher risk for subsequent psychosocial problems relative to children in comparison countries/regions, given linkages between insufficient sleep and poor academic and behavioral functioning in early childhood (91221). Indeed, although normative sleep requirements do vary on both individual and contextual levels, the average of 11.89 total hours of sleep for the samples in Korea is slightly lower than the 12 to 15 hours that infants and toddlers are thought to need (22). On the other hand, children in Korea also had less frequent and shorter night wakings than children in P-A countries/regions (but not P-C countries/regions), which could mean that nighttime sleep, while shorter for children in Korea, is more efficient and consolidated at nighttime compared to their counterparts in P-A countries/regions. Additionally, it may be that children in Korea require less sleep than infants and toddlers in other countries/regions or that these differences in total sleep do not have a significant impact on behavioral functioning (2), although research that tests these hypotheses is needed.

These findings merit further study and global comparisons, particularly in light of cross-cultural differences in parental perceptions of sleep problems (23). Despite the sample in Korea having less total sleep, rates of parent-identified “severe” child sleep problems were lower in both the Korea (2.3%) and P-C (2.2%) samples compared to the P-A sample (18.1%), although overall sleep problem endorsement was similar in Korea and P-A countries/regions (46.9% and 52.2%, respectively). It could be that lower levels of night wakings among infants and toddlers in Korea contributed to lower rates of parent-identified severe sleep problems compared to the P-A group. However, demographic variables (e.g., parent and child characteristics) have been found to be more predictive of parent-identified sleep problems among P-A countries/regions than sleep measures like estimates of night wakings (23). As such, the lower rate of parent-identified severe sleep problems in Korea compared to other P-A countries/regions could be due to unmeasured cultural factors, such as different socio-cultural expectations about child sleep habits or perceptions about what constitutes a “severe” versus a “small” sleep problem (23). Given that Sadeh et al. (23) found substantial heterogeneity in the extent to which parents of different countries/regions within the larger P-A group endorsed severe child sleep problems, future studies should focus on examining in more detail how sleep variables versus socio-cultural factors play a role in determining the severity of parent-reported child sleep concerns among P-A samples.

Study findings on rates of co-sleeping were consistent with previous research in this regard (824), and with the larger cross-cultural study from which these data were drawn (123). There were comparable rates of room-sharing and bed-sharing among families in Korea and in other P-A countries/regions. These co-sleeping rates were significantly higher than those of families in P-C countries/regions, where having children sleep in a separate bedroom is more common (824).

Findings for parental behaviors at sleep initiation and resumption within the Korea sample generally converge with the literature on this topic. For instance, rates of bottle-feeding, breastfeeding, rocking, and holding babies at sleep initiation all tended to decrease with increasing child age. Nursing back to sleep, giving the child a bottle, and holding or rocking the child back to sleep also decreased with older child age. Most of these trends are in line with parent behaviors at sleep initiation and resumption by child age reported in the larger cross-cultural examination of these data by P-A and P-C groups, which showed similar reductions in these initiation and resumption behavior with older child age (1). Of note, watching television at sleep initiation increased with older child age, and this behavior was also associated with later child bedtimes, as described further below.

Overall, few demographic, sleep ecology, and parental behavior variables emerged as predictors of significant variation (> 1%) in salient child sleep outcomes. However, child age explained 30.9% of the variance in daytime sleep duration and 23.3% of the variance in night wakings. These findings are consistent with literature showing that child sleep becomes increasingly consolidated at nighttime from infancy to toddlerhood (14181920). As mentioned previously, older child age was also associated with longer sleep episodes and nocturnal sleep, although age explained little variation in these outcomes.

Study findings support previous work indicating that active parent behaviors at sleep initiation or resumption, such as nursing or bottle-feeding, are associated with increased sleep fragmentation (1). In this sample, nursing and bottle-feeding predicted some variation in both nocturnal awakenings and longest sleep episodes. In particular, breastfeeding during the night accounted for 23.3% of the variance in nocturnal awakenings.

Importantly, watching television at sleep initiation was associated with having a later bedtime. This finding is of interest given that infants and toddlers in Korea have significantly later bedtimes and shorter total sleep times than children in both P-C and P-A countries/regions. In light of recent work in predominately Caucasian contexts linking the use of television or electronics at bedtime to insufficient sleep and other poor sleep-related outcomes, television habits, bedtime, and insufficient sleep should be studied further among infants, toddlers, and young children in Korea (141516). While it is premature to conclude that television at bedtime is causal in producing later bedtimes for children in Korea, these two variables appear to be linked, and are typically associated with insufficient sleep in other child samples (141516). Future studies should also examine other factors that could contribute to later bedtimes among infants and toddlers in Korea, especially as television watching and respondent age together explained only a small proportion of the total variance (4.0%) in this outcome.

Study findings are limited by the nature of the sample, which is confined to parents who elected to respond to an Internet-based survey on infant and toddler sleep. Internet-based surveys are likely skewed toward individuals of a higher socioeconomic status and educational background. Additionally, although the BISQ has been shown to be a reliable and valid measure of infant and toddler sleep, parent characteristics may have influenced their BISQ responses (17). Future studies should include objective measures to assess sleep/wake patterns. The cross-sectional nature of this study precludes any conclusions about causal relationships between any parental behaviors or demographics and child sleep outcomes. Longitudinal studies of infant and toddler sleep habits in Korea are necessary, as is research that examines other factors that could contribute to child sleep/wake patterns during this time period, such as bidirectional parent-child interactions (8) and socio-cultural perceptions or expectations about child sleep (23).

In conclusion, several findings from this study can be used to inform culture-specific research directions and clinical practices related to early childhood sleep in Korea. This study suggests that infants and toddlers tend to obtain less total sleep and have later bedtimes in Korea than their counterparts in P-A and P-C countries/regions. Furthermore, almost half of all parents perceive their children as having a sleep problem. Given the associations found in this study between bedtime behaviors (including feeding to sleep and television viewing) and later bedtimes and nighttime awakenings, pediatric practitioners should provide parents with information about healthy sleep habits to encourage positive sleep outcomes.