Prevalence of Sleep Disorder in Chinese Preschoolers: A National Population-Based Study

Introduction

A large number of studies have found that sleep problems are prevalent in childhood. Sleep disorders in children can lead to significant medical and behavioural problems, and children with sleep difficulties were also reported to experience higher rates of impaired cognitive function, learning disabilities, and mental and emotional problems.¹

An accurate report of the prevalence of sleep disorder in the healthy population is essential to provide the necessary guidelines to evaluate sleep difficulties in clinical practice. However, relatively few recent studies have addressed sleep patterns in preschoolers, and no studies are reporting sleep patterns or sleep disorder in Chinese preschool-aged children with a national sample according to our knowledge. Sleep behaviours and sleep problems in children are not only influenced by a wide range of biological and psychological factors but also by cultural and social factors, and in many reports, the prevalence rates of sleep disorders in childhood in different cultures are diversified.² Therefore, cultural sleep patterns and sleep disorder prevalence are needed to provide precise references to parents and clinical professionals.

The aims of this study were to (1) evaluate the prevalence of sleep disorder in Chinese children aged 3–5 years old with parent reports using the Children’s Sleep Habits Questionnaire (CSHQ); (2) describe sleep patterns and problems in Chinese preschoolers.

Materials and Methods

Study Design and Participants

Data were obtained from the Chinese National Cohort of Motor Development (CNCMD).^3,4 2403 nurseries from 551 cities in China were recruited and data was collected from 2018 to 2019. Stratified cluster sampling was used to ensure that the study participants were representative of the Chinese population. The China 2018–2019 National Census was used for stratification by geographic region, age, sex, and socioeconomic status. Children were excluded from the study if they had severe visual, hearing, intellectual impairments, cerebral palsy or other severe developmental disorders including autism spectrum disorder. A total of 114,311 children with complete information on personal characteristics were included in the final analysis (Figure 1).

Figure 1 Flowchart of the study population.

Outcomes

Sleep disorders of the children were assessed using the Children’s Sleep Habits Questionnaire (CSHQ)⁵ filled out by parents. The CSHQ is a widely used scale to measure the frequency of behaviours associated with common pediatric sleep difficulties, which has acceptable reliability and validity in Chinese children⁶ The 33 parent-rated items of the questionnaire are grouped into eight subscales: Bedtime Resistance, Sleep Onset Delay, Sleep Duration, Sleep Anxiety, Night Wakings, Parasomnias, Sleep Disordered Breathing, and Daytime Sleepiness. All eight subscales’ ratings are summed to create a total sleep disorder index. A higher CSHQ score indicates more sleep difficulties, and a total score of over 41 indicates a pediatric sleep disturbance.⁵ Daily sleep hours were also reported by parents as the value of 5/7×Sleep hours during weekdays+2/7×Sleep hours at the weekends.

Statistical Analysis

Differences in the CSHQ scores, the prevalence of sleep disorder, subscale scores of CSHQ, and daily sleep hours by sex and ages were analyzed using independent t-tests, and Chi-squared tests. A statistical significance level was set at a p-value <0.05 (two-tailed). The 95% confidence interval of the prevalence of sleep disturbance was calculated using the Wald method.⁷

Results

Of the 114,311 children included in the final analysis, the average daily sleep hours are 10.72 with a standard deviation of 2.69, and 87,773 children (76.78%,95% CI: 76.54%, 77.03%) were reported to have a sleep disorder. Bedtime Resistance was reported most frequently as a problem in Chinese children’s sleep (97.00%, 95% CI: 95% CI:96.90%, 97.10%), other sleep problems including Daytime Sleepiness (77.68%, 95% CI::77.43%, 77.92%), Sleep Duration (70.24%, 95% CI: 69.97%, 70.50%), Parasomnia (58.52%, 95% CI: 58.23%, 58.80%), Sleep Anxiety(55.53%, 95% CI::55.24%, 55.81%), Sleep Onset Delay (51.99%, 95% CI: 95% CI:51.70%, 52.28%) Night Wakings (30.37%, 95% CI: 30.10%, 30.63%) and Sleep Disordered Breathing (21.86%, 95% CI: 21.62%, 22.09%).

Table 1 shows the CSHQ scores and the prevalence of sleep disorder by sex and age. Girls had higher total scores of CSHQ and had a higher prevalence of sleep disorder. Girls also had more problems on subscales of Sleep Duration, Daytime Sleepiness, and Sleep Anxiety, and fewer problems with Bedtime Resistance, Parasomnia, and Sleep Disordered Breathing than boys. The daily sleep hours, and the subscores of Sleep Onset Delay or Night Wakings were not influenced by sex (each p>0.05) (Table 1). Younger children had more disturbances than the older ones, reflected in the total score, the subscores of Sleep Onset Delay, Night Wakings, and Parasomnia. Younger children had longer daily sleep hours, and fewer problems with Bedtime Resistance, Sleep Duration, Sleep Anxiety, Sleep Disordered Breathing, and Daytime Sleepiness (each p<0.05) (Table 1).

Table 1 The Sex and Age-Specific Sleep Problems in Preschool Children (n=114,311)

Discussion

The prevalence of sleep disorders in healthy Chinese preschoolers was reported in the current study with a large nationally representative sample. Sleep disorder defined with a CSHQ score was found to be prevalent in 76.78% of Chinese preschoolers. Bedtime resistance was reported as the most frequently reported sleep problem by parents of Chinese children.

The remarkably high incidence of CSHQ-indicated sleep disorder is consistent with previous studies using the CSHQ which also reported a very high prevalence of sleep disorders in Japanese preschoolers and Chinese preschoolers with smaller multi-regional samples,⁸ but higher than the reports in western culture.^9–11 The clinical cutoff for a global sleep disorder on the CSHQ was based on data obtained from American children,⁵ and our results suggest the cultural features in the sleep behaviours of children, and a local standard may be required when using the CSHQ to define sleep disorders in Chinese children. The CSHQ is a widely used tool in clinical settings to screen children’s sleep problems including in China, and our results suggested that the CSHQ should be used with great caution, especially in preschoolers considering the very high incidence of sleep disorder in Chinese children as defined by the CSHQ. Previous studies reported that environmental factors such as air pollution¹² and co-sleeping¹³ may be the reasons explaining the cultural differences in childhood sleep patterns. However, what is considered normal sleep by parents in different cultures, and both subjective and objective sleep measurements with cross-culture populations should also be further investigated for a better understanding of cultural influences on sleep.

Child age was associated with almost all sleep problems. Specific sleep disturbances in Sleep Onset Delay, Night Wakings and Parasomnia were more common in younger children; and Bedtime Resistance, Sleep Duration, Sleep Anxiety, Sleep Disordered Breathing and Daytime Sleepiness were more prevalent in older children, which might reflect the child’s normal development. Girls had a higher prevalence of sleep disorder and generally experienced more sleep problems than boys but not in all areas. This demonstrated important features in the sleep patterns of Chinese children. Future research should be conducted to investigate the mechanism underlying age- and sex-variance of sleep to examine if it is necessary to develop the sex- and age-specific norms for the CSHQ.

The current study was the first to report the national prevalence of sleep disorder in preschoolers with a large national representative sample. However, our study also had the limitation. In our study, the parent-filled CSHQ was used to measure sleep disorder which may lead to subjective bias or inaccuracy. Thus, large-scale studies using objective measures of sleep instead of parent reports would add substantially to the theoretical and practical utility of future findings.

Conclusion

The high prevalence of sleep disorders in healthy Chinese preschoolers is comparable to the percentages previously reported in East Asia but remarkably higher than in Western countries. Specific sleep problems of Chinese preschoolers vary from other cultures. An in-depth investigation into the reasons for these cultural sleep differences in children should be conducted in future research using a culturally sensitive and comparable approach to ensure appropriate supportive intervention. Our study also emphasized the importance to include the establishment of culturally appropriate norms in studying child sleep.