This meta-analysis and systematic review was conducted to evaluate the prevalence rates of sleep disorders among children in Mainland China and characterize the epidemiology of sleep disorders. Through analysis, we identified several characteristics of sleep disorders in Mainland China. Firstly, the point estimate for sleep disorders prevalence obtained in males was higher than in females. Secondly, the prevalence of sleep disorders among the Chinese school-age population observed in this study was observably high. Furthermore, various age groups could impact the prevalence estimation. Thirdly, the prevalence was obviously higher in West China than in South China(47.4% vs. 30.4%). Fourthly, the prevalence of sleep disorders slightly increased over the past two decades (from the point prevalence of 37.6% before 2006 to 39.2% after 2006). Fifthly, the pooled prevalence of sleep disorders among children could be impacted by the application of different questionnaire reference criteria.
Our study showed that the prevalence rates of sleep disorders among children in mainland China ranges from 15.3–76.3%, which was higher than in Europe and the United States(25%). It may be related to the existence of differences in the subjects' own sleep disorders, as well as to the evaluation tools used in the study to assess children's sleep disorders, the screening year of the study, the economic and cultural differences in the study area, feeding practices, and various all kinds of questionnaire reference criteria or diagnostic criteria.In addition, sleep disorders among children may also be closely related with China's traditional culture which places greater emphasis on the cultivation of children's sense of family closeness (e.g., children sleeping in the same bed with parents), indulgently parenting style (e.g., children having a TV or computer in the bedroom), relatively overcrowded housing (e.g., small per capita housing area), and the lack of parental attention to children's sleep hygiene.The present study identified a higher prevalence of sleep disorders in boys than in girls, which may correlated with sex differences in the anatomy and physiology of the upper airway between males and females. What's more, most boys are overly excited during the day,and the cerebral cortex is still in an excited state after sleep, prone to teeth grinding, night terrors, nightmares, sleepwalking or other sleep problems. However, studies have also shown that estrogen, as a protective hormone, can stabilize the respiratory control system and reduce the occurrence of apnea during sleep. The prevalence of sleep problems in children increase with age, which may be related to a variety of reasons, including a higher burden of coursework and academic stress in older children. Moreover, preschoolers and school-age children may be under the academic pressure to the process of children's transition including from kindergarten to primary school or elementary-school to junior high-school,combined with excessive daytime excitement and reduced sleep intake, which may lead to an increased incidence of teeth grinding.
There may be several reasons why the prevalence rates of sleep disorders among children in the western China was significantly higher than in the coastal areas of southern China.First, poor sleep habits are associated with backward regional cultural attitudes, such as having dinner just before bedtime, habit of the midnight snack, difficulty falling asleep alone, and needing assistance to fall asleep, etc., which result in inadequate sleep duration. Second, parental work schedules and sleep habits may have a direct impact on children's late sleep, insufficient sleep duration and poor sleep quality.The prevalence of sleep disorders has increased compared to previous studies. The development of the society and the increasing competitive pressures in the different years investigated may directly or indirectly affect sleep deprivation, poor sleep quality and irregular sleep patterns. In addition, the rapid economic development in mainland China has made electronic products (such as smartphones, tablet computers, laptops, etc.) widely popularized and applied, which may inhibit the brain's secretion of melatonin, leading to hyper-excitement and light sleep in children.
At present, the epidemiological investigation of sleep disorders among children mainly adopts a questionnaire survey to carry out a wide range of screening. In mainland China, the Chinese version of an epidemiologic survey questionnaire from the Sleep Center of the Sydney Children’s Hospital and Sydney University and Children's Sleep Habits Questionnaire (CSHQ), the Sleep Status of Self-rating Scale, and the Pittsburgh Sleep Quality Index (PSQI) are widely used to screen for sleep problems. Generally, parents completed the questionnaire, including information on child feeding at birth, children's sleep, parents' sleeping conditions, the incidence of respiratory illnesses, children's or parents' personal conditions, family environment, etc.. Various reference standards or questionnaires have also contributed to the wide variation in the results of the incidence of sleep problems, and continued research and improvement in future clinical work is needed.
This meta-analysis has its own limitations. Firstly, males included were more than females, which may have lead to an overestimation of the prevalence rate of sleep disorders. Secondly, the prevalence of sleep disorders in all included studies increased with increased age, especially among school-age children. In addition, the age-group categorized differently was associated with the high heterogeneity in all or subgroups analyses. Although we also identified different age groups as possible influencers of these results, the extent of this explanation was very limited. Thirdly, most of the included studies were conducted in the developed regions in mainland China. And some included studies conducted at the relatively backward western regions have an observably high prevalence of sleep disorders, which could lead to widely varying and poorly representative results. Nevertheless, our study had a large sample size and was in line with the PRISMA statement. The sample in the included studies was drawn from a sample survey, and the included cases were screened and clearly diagnosed, so the results have some confidence.