As a behavioral scientist, I read pediatric sleep research to better understand what factors can influence sleep. I am reading articles beyond those related to assessment and treatment. The Wu et al. (2018) paper caught my attention due to sleeping differences between regions captured within the same country.

In a previous post, I looked at how pediatric sleep varies across countries (Mindell et al., 2010, 2013). In this post, I look at how those differences show up within one country.

Within China, what counts as a typical bedtime, wake time, and amount of sleep shifts by nearly an hour from one region to another. As such, it is important to talk with each family about what is typical for their region, not the national average.

A 4.5-year-old in China wakes at 7:30 AM. In one province, that is among the earliest wake times in her class. In another, it is among the latest. Both children live on the same Beijing clock and follow the same national sleep recommendations.

In eastern China, 16.9% of preschoolers slept less than the 10-hour minimum. In western China, 9.3% did not meet the same criterion. Same country, same threshold, nearly twice the rate of insufficient sleep in one region.

Wu et al. (2018) collected parent reports on 1,610 Chinese preschoolers, ages 3 to 6, across 10 cities, from November 2012 through January 2013. They split the sample by time zone: 1,201 children in eastern China (UTC+8, on Beijing time, the wealthier eastern coast including Shanghai and Beijing) and 409 children in western China (UTC+7 and UTC+6, including Xinjiang and Tibet). Sleep variables were measured using questions adapted from the Children’s Sleep Habits Questionnaire.

The five figures below were built from data tables in the Wu paper. These exact figures do not appear in the source paper.

In the United States and across much of the Western literature, lower-income neighborhoods are associated with shorter sleep in children. In China, the wealthier and more developed eastern provinces are the ones whose children sleep less. Wu et al. speculated that evening academic tutoring, screen time, and competition for primary-school admission were associated with the differences across regions.

Data in the figure above represent the mean bedtime, in Beijing clock time, on weeknights, by region and age. Children in eastern China went to bed about 20 minutes earlier than children in western China across the four ages, and the spread of bedtimes within each region (the whiskers) overlapped considerably. The bedtime gap was small but consistent.

Data in the figure above represent the average wake time, in Beijing clock time, on weekday mornings, by region and age. The wake-time gap was much larger than the bedtime gap. Children in eastern China awoke about 40 minutes earlier than children in western China, and within each region the spread was reasonably tight, around 28 minutes on either side of the mean. In standardized terms (Cohen's d = 1.24), this is the largest within-country effect Wu et al. report.

Data in the figure above show each region's full weekday sleep window, age by age, on a single 24-hour clock. The eastern-China band sits earlier; the western-China band sits later. The two bedtimes are close, but the wake times are clearly displaced. Across the four ages, the east-to-west gap within China was consistent.

Data in the figure above represent how many minutes later children went to bed and woke up on weekends than on weekdays, by region and age. Both regions showed a delayed bedtime and wake time; western China slides further at both ends. The wake delay in western China (the dashed orange line) sits at the top of the chart at every age, with the bedtime delay in western China just below it. The wake delay and bedtime delay in eastern China sit clustered together at the bottom. The western-China lines stay roughly 10 to 30 minutes above the eastern-China lines across the full four-year age range.

Wu et al. attributed the shortfall in sleep in eastern China to a specific stack of evening pressures, in their words (pp. 537–538):

"For example, children in eastern China are more likely to participate in mathematics tutoring, piano lessons, and other extracurricular activities at night in order to gain entry to a better primary school. Digital technology use is more popular among children in eastern China." Wu et al., 2018, p. 538

From a behavioral perspective, the question is what fills the evening in each region. Children in eastern China are not sleeping as much due to their delayed bedtime. Math tutoring, piano lessons, and screen time may push the bedtime hour later in the wealthier provinces. Children in western China, whose families face less competitive primary-school pressure, more often have earlier bedtimes

Wu et al. closed their paper with a recommendation for parents and policy:

"It is recommended that parents in China allow and support their children to get enough sleep according to the recommended NSF sleep time through the maintenance of a stable sleep pattern throughout the week, in order to avoid misalignment." Wu et al., 2018, p. 539

What counts as early or late, and what counts as enough sleep, depends on where in China a child lives, how far local solar time runs from Beijing time, and what evening practices are common in their region. Every conversation about a child’s sleep should begin with the family’s actual bedtime, wake time, and the activities that fill their evenings. The national average is a reference point, not the schedule the child experiences each night.

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References

Hirshkowitz, M., Whiton, K., Albert, S. M., Alessi, C., Bruni, O., DonCarlos, L., Hazen, N., Herman, J., Katz, E. S., Kheirandish-Gozal, L., Neubauer, D. N., O’Donnell, A. E., Ohayon, M., Peever, J., Rawding, R., Sachdeva, R. C., Setters, B., Vitiello, M. V., Ware, J. C., & Adams Hillard, P. J. (2015). National Sleep Foundation’s sleep time duration recommendations: Methodology and results summary. Sleep Health, 1(1), 40–43. https://doi.org/10.1016/j.sleh.2014.12.010

Mindell, J. A., Sadeh, A., Wiegand, B., How, T. H., & Goh, D. Y. T. (2010). Cross-cultural differences in infant and toddler sleep. Sleep Medicine, 11(3), 274–280. https://doi.org/10.1016/j.sleep.2009.04.012

Mindell, J. A., Sadeh, A., Kwon, R., & Goh, D. Y. T. (2013). Cross-cultural differences in the sleep of preschool children. Sleep Medicine, 14(12), 1283–1289. https://doi.org/10.1016/j.sleep.2013.09.002

Paruthi, S., Brooks, L. J., D’Ambrosio, C., Hall, W. A., Kotagal, S., Lloyd, R. M., Malow, B. A., Maski, K., Nichols, C., Quan, S. F., Rosen, C. L., Troester, M. M., & Wise, M. S. (2016). Recommended amount of sleep for pediatric populations: A consensus statement of the American Academy of Sleep Medicine. Journal of Clinical Sleep Medicine, 12(6), 785–786. https://doi.org/10.5664/jcsm.5866

Wu, R., Wang, G.-H., Zhu, H., Jiang, F., & Jiang, C.-L. (2018). Sleep patterns in Chinese preschool children: A population-based study. Journal of Clinical Sleep Medicine, 14(4), 533–540. https://doi.org/10.5664/jcsm.7038

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A four-year-old sleeps in their parents’ bed. Is that a sleep concern? It is essential that we talk with each family because there are notable cultural differences in where children sleep, when they go to bed, when they wake up, and if they nap.

In the United States, about three-quarters of preschoolers sleep in their own room. In China, fewer than 7% do (Mindell et al., 2013).

In a previous post, I looked at parent-reported sleep durations of children across four countries (Iglowstein and colleagues, 2003, Switzerland; Schlarb and colleagues, 2015, Germany; Cespedes and colleagues, 2014, USA; Li and colleagues, 2013, China). Children’s total sleep durations varied considerably depending on where the children were raised.

In this post, I am looking at the larger cross-cultural sleep surveys. The two papers led by Dr. Jodi Mindell and colleagues (2010, 2013) collected parent-reported sleep variables from 29,287 infants and toddlers (ages 0 to 36 months) across 17 countries, and from 2,590 preschoolers (ages 3 to 6 years) across 13 of those same countries. The two studies used the same questionnaire framework, which allowed us to look at different aspects of sleep across the first six years.

The four figures below were built from the data tables and graphs published in the two Mindell papers. I plotted values from both studies on the same axes so the developmental and cross-cultural patterns can be read across the first six years on the same page. The exact figures shown here do not appear in either source paper.

One reason these comparisons matter for clinical practice and for parents was stated by Mindell et al. (2006):

“In addition, culturally-based values and beliefs regarding the meaning, importance, and role of sleep in daily life, as well as culturally-based differences in sleep practices (e.g., sleeping space and environment, solitary sleep vs. co-sleeping, use of transitional objects) have a profound effect not only on how a parent defines a sleep ‘problem’ but on the relative acceptability of various treatment strategies.” Mindell et al., 2006, p. 1264

Data in the figure above are from the two Mindell studies and are plotted across the first six years. The cross-cultural gap in total sleep was already present in infancy. Mindell et al. (2010) reported an aggregate difference of 0.71 hours, or about 43 minutes, between predominantly Caucasian and predominantly Asian infants and toddlers, with the predominantly Caucasian group sleeping more.

Data in the above figure represent bedtimes for 17 countries at infant and toddler ages on the left column and 13 countries at preschool ages on the right column. Bedtimes varied across countries by almost 3 hours at both ages, but there were notable degrees of variability for each country. New Zealand, the United Kingdom, and Australia had the earliest group means at every age (before 8:00 PM). India and Hong Kong have the latest at both ages (after 10:00 PM); South Korea is among the latest at infant and toddler ages but slightly earlier at preschool age (about 9:55 PM). The country rankings, for the most part, remained stable from infancy through preschool.

Data in the above figure represent the percentage of children who sleep in their own room across countries. This was the largest cross-cultural effect in either Mindell paper (effect size φ = .70 in the 2013 paper). In countries grouped as predominantly Caucasian, most children slept in their own room from infancy onward. In countries grouped as predominantly Asian, the percentage of families for which a child slept in their own-room remained low at both age groups and remained in single digits in several countries through age 6. As such, what counts as "on track" for sleeping in their own room is a cultural question more than a developmental one. This is critical as we work with families and schools on improving pediatric sleep.

Data in the above figure represent the percentage of parents reporting a consistent bedtime routine on most nights. The two papers used different thresholds (Mindell et al., 2010 used “more than 4 nights per week” and Mindell et al., 2013 used “3 or more nights per week”). Countries grouped as predominantly Caucasian reported consistent routines at higher percentages than countries grouped as predominantly Asian.

Where a child sleeps and when a child goes to bed differ across the world. What looks like a problem in one country is a cultural expectation in another one. This is why every discussion about a potential sleep concern requires listening to what is valued by the family at the start and throughout the assessment and treatment process.

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References

Mindell, J. A., Kuhn, B., Lewin, D. S., Meltzer, L. J., & Sadeh, A. (2006). Behavioral treatment of bedtime problems and night wakings in infants and young children. Sleep, 29(10), 1263–1276. https://doi.org/10.1093/sleep/29.10.1263

Mindell, J. A., Sadeh, A., Wiegand, B., How, T. H., & Goh, D. Y. T. (2010). Cross-cultural differences in infant and toddler sleep. Sleep Medicine, 11(3), 274–280. https://doi.org/10.1016/j.sleep.2009.04.012

Mindell, J. A., Sadeh, A., Kwon, R., & Goh, D. Y. T. (2013). Cross-cultural differences in the sleep of preschool children. Sleep Medicine, 14(12), 1283–1289. https://doi.org/10.1016/j.sleep.2013.09.002

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In clinical practice, I focus on applying practical assessment and intervention approaches. I will share my experiences on those in the future. For now, I am looking at what sleep looks like across cultures and countries.

In a previous post, I re-graphed data from the National Sleep Foundation’s 2026 survey of North American families alongside sleep guidelines from the National Sleep Foundation and the American Academy of Sleep Medicine. One implication for practice is that more awareness of the recommended total sleep durations is warranted, which could inform the timing of children’s bedtime. You can toggle on and off the different studies in the visual here.

As I have continued to look at research on sleep timing and duration of children, I noticed parent-reported sleep durations published by research teams from different countries. I was interested in studies that provide fine-grained, parent-reported sleep duration data in 1-year or 1.5-year intervals rather than aggregating across wide age bands (e.g., 3 to 5 year olds, 6 to 13 year olds). Below is a visual I created comparing data from four studies of families in the USA, Switzerland, Germany, and China.

You can toggle off and on the mean data from each country as well as the variability bands in the interactive graphical depiction here.

Above are data from Iglowstein and colleagues (2003; Switzerland) and Schlarb and colleagues (2015; Germany). The lines represent means; the bands represent the 25th to 75th percentile (50% of children). Swiss children slept 30 to 50 min longer than German children from about age 1 to age 6. The Iglowstein et al. cohorts were born between 1974 and 1993, which is 10 to 30 years before the other three studies collected their data. It is plausible that the sleep durations of Swiss children have decreased since the study was conducted, which would be consistent with a trend of later bedtimes and relatively unchanged wake times observed across the Swiss cohorts in the Iglowstein study.

Above are additional data from a Massachusetts (USA) cohort and Chinese families as obtained by Cespedes and colleagues (2014) and Li and colleagues (2013), respectively. On average, North American children slept less than German and Swiss children. Children in China slept the least for older age ranges.

The graph above shows pairwise differences between countries at each age. For example, German children slept more than American children across all overlapping ages, as indicated by the blue data points in the bottom left panel.

These data are descriptive, and there are differences in when and how these data were obtained. How much children sleep varies considerably depending on where and when children are raised. Cultural practices around bedtime (e.g., finishing academic work, later mealtimes, screen use near bedtime) and wake times likely contribute to these differences. This will be explored more in the future.

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The Study - National Sleep Foundation. (2026). Sleep in America Poll: A focus on America’s youngest sleepers

The National Sleep Foundation has conducted the Sleep in America Poll since 1991, with each edition focusing on a different theme (e.g., teens, technology). In 2004, The National Sleep Foundation surveyed parents of children up to age 10. The 2026 edition returned to children and families, covering ages 0 to 13.

The NSF surveyed 977 parents and caregivers in English and Spanish around September 2025. The sample included 53% biological mothers, 33% biological fathers, and 14% other caregivers (i.e., step-parents, grandparents, aunts, and uncles). The children are represented four age groups: 206 under 1 year old, 320 ages 1 to 2, 207 ages 3 to 5, and 244 ages 6 to 13.

All of these data are based on parent report. Parents are not always in the room when a child falls asleep, and they are not there when the child wakes at night without making enough noise to alert them. Every number in this poll reflects a subjective estimate.

The Commonly Referenced Standards for Sleep Durations

In 2015 and 2016, two independent organizations reviewed the evidence as perceived by sleep experts. The National Sleep Foundation convened 18 experts who reviewed 312 studies. The American Academy of Sleep Medicine assembled 13 experts who reviewed 864 studies. Three of five shared age groups got identical ranges. Where they differed, the gap was one hour.

The National Sleep Foundation’s 2026 survey data used the Hirshkowitz and colleagues (2015) ranges as the benchmark when they surveyed 977 parents. They asked: How much sleep does your child need? At every age group, the average parent estimate fell below the recommended range.

Because parents are not familiar with the recommended sleep ranges, it may be one factor leading to children not meeting the age-based sleep recommendations.

In Addition to Parents Underestimating How Much Sleep is Needed, Parents Overestimate their Child’s Sleep when Compared to Objective Measures (i.e., actigraphy).

From Prokasky and colleagues (2019), parents overestimate how much their young child sleeps. When 185 toddlers wore wrist actigraphy devices for two weeks, parents overestimated their child's sleep by 2 hours and 10 minutes per night.

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