Brief Report: An Epidemiologic Survey of the Prevalence of Sleep Disorders Among Children 2 to 12 Years Old in Beijing, China
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《小儿科》
the Department of Respiratory Medicine, Beijing Children's Hospital, Affiliated with Capital University of Medical Sciences, Beijing, People's Republic of China
ABSTRACT
Objective. This survey was conducted to examine the prevalence of sleep disorders in 2- to 12-year-old children in the Beijing area of China.
Methods. From October 2001 to June 2002, 5979 children 2 to 12 years old in 6 randomly selected counties in Beijing were investigated with questionnaires.
Results. The average total sleep time per day ranged from 11.38 hours among 2-year-olds down to 9.34 hours among 12-year-olds. The overall prevalence of sleep disorders was 21.2% and included parasomnia symptoms (bruxism [6.5%], sleep talking [4.9%], enuresis [1.0%], sleepwalking [0.6%], restless sleep [5.0%], and leg movements [1.9%]) and symptoms of sleep-disordered breathing (frequent snoring [5.6%], mouth breathing [4.1%], choking/gasping [0.9%], and breathing pauses [0.2%]).
Conclusion. The overall prevalence of parent-reported symptoms of sleep disorders in a large sample of children in Beijing, China, was comparable to that reported in other countries, although the prevalence of some specific symptoms differed somewhat.
Key Words: children sleep sleep disorders
Sleep is an important physiologic process in human beings, occupying one third of a lifetime. Among children, sleep quality is directly associated with physical health, development of intelligence, and emotional growth.1,2 Few studies have examined sleep problems in one of the world's largest pediatric populations, that of mainland China. Previous studies have focused primarily on behavioral sleep problems (eg, night waking, bedtime struggles). This survey was conducted to examine the prevalence and correlates of symptoms associated with organic sleep disorders, specifically symptoms of sleep-disordered breathing, parasomnias, and restless sleep, in a large sample of children 2 to 12 years old in the Beijing area of China.
METHODS
October 2001 through June 2002, 5979 children 2 to 12 years old were investigated via questionnaires in 6 randomly chosen counties in Beijing: 2 city zones (highest socioeconomic status), 2 counties on the plains, and 2 counties in a mountainous area (lowest socioeconomic status). In each region, 2 or 3 kindergartens and primary schools were selected randomly, from which 100 children in each age group were chosen. The survey was conducted in the schools. We obtained consent from parents and human-subject approval from the local health bureau before conducting the survey.
An epidemiologic survey questionnaire from the Sleep Center of the Sydney Children's Hospital and Sydney University in Australia was adapted, translated into Chinese, and revised for regional dialects. The questionnaire consisted of 28 items addressing birth, prenatal, and feeding history; sleep-related items (sleep disorders [frequent snoring, choking/gasping, mouth breathing, breathing pauses] bruxism, sleep talking, sleepwalking, leg movements, and restless sleep); and respiratory diseases (eg, asthma). Parents were asked to answer sleep-related questions regarding their children's sleep in the previous 12 months. Most of the questions were yes/no items; parents had to supply numbers or frequencies for 9 items.
The investigators who conducted the survey were all trained to explain and ask questions in a uniform manner to ensure consistency and quality of findings. We conducted a pretest consistency check by having all the investigators ask the same question of the same parent and verifying concordance of responses. The investigators checked their own and one another's questionnaires. During the survey, the school principals from different regions checked questionnaires randomly in their counties to ensure integrity and quality of responses. Five percent of questionnaires were checked in this way.
For statistical analysis, the 2 test was used to assess the effects of age, gender, and region on sleep problems. All analyses were performed by using the Statistical Program for the Social Sciences (SPSS) for Windows, version 10.0. All statistical significance was set at P < .05.
RESULTS
The total sample number was 6600, a 90.6% response rate. To gain an overview of the differences between age groups, we created 4 categories: toddler (2 years old), preschool (3–5 years old), grammar school (6–10 years old), and middle school (11–12 years old).
Time Spent Sleeping
The mean duration of sleep per day for each group and the proportions of each age group sleeping different numbers of hours per day are shown in Table 1. As would be expected, sleep duration decreased as age increased.
Prevalence of Sleep Disorders
In our study, the total prevalence of sleep disorders, defined as the parent reporting the presence of any symptom, was 21.2%. Disorders included parasomnia symptoms (bruxism [6.5%], sleep talking [4.9%], and sleep walking [0.6%]); restless legs/periodic limb movement symptoms (restless sleep [5.0%] and leg movements [1.9%]); and symptoms of sleep-disordered breathing (frequent snoring [5.6%], mouth breathing [4.1%], choking/gasping [0.9%], and breathing pauses [0.2%]).
The prevalence of bruxism was significantly higher in the preschool (8.5%) and grammar-school (6.7%) groups than in the toddler (3.5%) and middle-school (3.7%) groups (P < .002). The prevalence of restless sleep ranged from 9.6% among 2-year-olds down to 3.4% among 12-year-olds (P > .001). The prevalence by age group is shown in Table 2.
There were significant differences between regions in the prevalence of snoring, mouth breathing, and restless sleep, all higher in the city area (Table 3). Snoring prevalence was 7.7% in the city area, 5.4% in the plains area, and 4.1% in the mountain area (P = .004, city versus plains; P > .001, city versus mountain); the prevalence of mouth breathing was 5.4% in the city area, 3.8% in the plains area, and 3.3% in the mountain area (P = .016. city versus plains; P = .001, city versus mountain); and the prevalence of restless sleep was 7.1% in the city area, 3.9% in the plains area, and 4.3 in the mountain area (P = .016, city versus plains; P = .001, city versus mountains).
In addition, there were some significant differences between boys and girls. Overall, boys had more sleep disorders than did girls (22.4% vs 19.8%; P = .013). Boys also experienced significantly more snoring (6.7% vs 4.5%; P > .001) and mouth breathing (4.7% vs 3.4%; P = .013) than did girls (Table 4).
DISCUSSION
The amount of time that people spend sleeping has decreased remarkably with technical progress and changes in lifestyle. At present, sleep duration has decreased by 20% to 25%; however, no significant effects of this decrease on growth, overall health, or lifespan have been seen.3 In our survey, the average daily sleep duration of children 2 to 5 years old was 1 hour shorter than that reported in the Nelson Textbook of Pediatrics,4 demonstrating that insufficient sleep is very common among young children.
Our study showed that the overall prevalence of sleep disorders among children in the Beijing area (21.2%) was similar to that in Western countries (20–25%),5 suggesting that childhood sleep disturbance is very common in Beijing.
The prevalence of sleep disorders in children is related to age, and the occurrence of symptoms is related to stages of physical development. Between 3 and 10 years of age, most children are developing permanent teeth. Growth of the teeth and stimulation of sprouting teeth may cause bruxism during this period.
our research, we found that the prevalence of snoring, mouth breathing, and restless sleep is higher in the city than in the rural area, which is probably because of living conditions, economics, culture, educational level of parents, and other factors. Additional research is necessary to determine the exact causes.
CONCLUSIONS
Childhood sleep disorders are very common in Beijing. Additional research is necessary to clarify the correlates between sleep disorders and age, gender, feeding, geographical location, and physical diseases. The causes and effects of insufficient sleep in young children should be investigated to improve the quality of children's sleep.
FOOTNOTES
Accepted Aug 5, 2004.
No conflict of interest declared.
REFERENCES
Liu X, Lin C, Xue Q, Qian Q. Child Health Care. Nanjing, China: Jiangsu Science and Technique Press; 1989:101
Dahl RE. The impact of inadequate sleep on children' s daytime cognitive function. Semin Pediatr Neurol. 1996;3 :44 –50
You G, Zhu S, Zhang K. Insomnia and sleep disordered disease. People’s Army Med Press. 1999:30
Richard EB, Robert MK, Hal BJ. Growth and development. In: Richard EB, Robert MK, Hal BJ, eds. Nelson Textbook of Pediatrics. 16th ed. Philadelphia, PA: W. B. Saunders Co; 2000:32 –36
Mindell JA, Owens JA, Carskadon MA. Developmental features of sleep. Child Adolesc Psychiatr Clin N Am. 1999;8 :695 –725(Xicheng Liu, MD, Yuyan Ma)
ABSTRACT
Objective. This survey was conducted to examine the prevalence of sleep disorders in 2- to 12-year-old children in the Beijing area of China.
Methods. From October 2001 to June 2002, 5979 children 2 to 12 years old in 6 randomly selected counties in Beijing were investigated with questionnaires.
Results. The average total sleep time per day ranged from 11.38 hours among 2-year-olds down to 9.34 hours among 12-year-olds. The overall prevalence of sleep disorders was 21.2% and included parasomnia symptoms (bruxism [6.5%], sleep talking [4.9%], enuresis [1.0%], sleepwalking [0.6%], restless sleep [5.0%], and leg movements [1.9%]) and symptoms of sleep-disordered breathing (frequent snoring [5.6%], mouth breathing [4.1%], choking/gasping [0.9%], and breathing pauses [0.2%]).
Conclusion. The overall prevalence of parent-reported symptoms of sleep disorders in a large sample of children in Beijing, China, was comparable to that reported in other countries, although the prevalence of some specific symptoms differed somewhat.
Key Words: children sleep sleep disorders
Sleep is an important physiologic process in human beings, occupying one third of a lifetime. Among children, sleep quality is directly associated with physical health, development of intelligence, and emotional growth.1,2 Few studies have examined sleep problems in one of the world's largest pediatric populations, that of mainland China. Previous studies have focused primarily on behavioral sleep problems (eg, night waking, bedtime struggles). This survey was conducted to examine the prevalence and correlates of symptoms associated with organic sleep disorders, specifically symptoms of sleep-disordered breathing, parasomnias, and restless sleep, in a large sample of children 2 to 12 years old in the Beijing area of China.
METHODS
October 2001 through June 2002, 5979 children 2 to 12 years old were investigated via questionnaires in 6 randomly chosen counties in Beijing: 2 city zones (highest socioeconomic status), 2 counties on the plains, and 2 counties in a mountainous area (lowest socioeconomic status). In each region, 2 or 3 kindergartens and primary schools were selected randomly, from which 100 children in each age group were chosen. The survey was conducted in the schools. We obtained consent from parents and human-subject approval from the local health bureau before conducting the survey.
An epidemiologic survey questionnaire from the Sleep Center of the Sydney Children's Hospital and Sydney University in Australia was adapted, translated into Chinese, and revised for regional dialects. The questionnaire consisted of 28 items addressing birth, prenatal, and feeding history; sleep-related items (sleep disorders [frequent snoring, choking/gasping, mouth breathing, breathing pauses] bruxism, sleep talking, sleepwalking, leg movements, and restless sleep); and respiratory diseases (eg, asthma). Parents were asked to answer sleep-related questions regarding their children's sleep in the previous 12 months. Most of the questions were yes/no items; parents had to supply numbers or frequencies for 9 items.
The investigators who conducted the survey were all trained to explain and ask questions in a uniform manner to ensure consistency and quality of findings. We conducted a pretest consistency check by having all the investigators ask the same question of the same parent and verifying concordance of responses. The investigators checked their own and one another's questionnaires. During the survey, the school principals from different regions checked questionnaires randomly in their counties to ensure integrity and quality of responses. Five percent of questionnaires were checked in this way.
For statistical analysis, the 2 test was used to assess the effects of age, gender, and region on sleep problems. All analyses were performed by using the Statistical Program for the Social Sciences (SPSS) for Windows, version 10.0. All statistical significance was set at P < .05.
RESULTS
The total sample number was 6600, a 90.6% response rate. To gain an overview of the differences between age groups, we created 4 categories: toddler (2 years old), preschool (3–5 years old), grammar school (6–10 years old), and middle school (11–12 years old).
Time Spent Sleeping
The mean duration of sleep per day for each group and the proportions of each age group sleeping different numbers of hours per day are shown in Table 1. As would be expected, sleep duration decreased as age increased.
Prevalence of Sleep Disorders
In our study, the total prevalence of sleep disorders, defined as the parent reporting the presence of any symptom, was 21.2%. Disorders included parasomnia symptoms (bruxism [6.5%], sleep talking [4.9%], and sleep walking [0.6%]); restless legs/periodic limb movement symptoms (restless sleep [5.0%] and leg movements [1.9%]); and symptoms of sleep-disordered breathing (frequent snoring [5.6%], mouth breathing [4.1%], choking/gasping [0.9%], and breathing pauses [0.2%]).
The prevalence of bruxism was significantly higher in the preschool (8.5%) and grammar-school (6.7%) groups than in the toddler (3.5%) and middle-school (3.7%) groups (P < .002). The prevalence of restless sleep ranged from 9.6% among 2-year-olds down to 3.4% among 12-year-olds (P > .001). The prevalence by age group is shown in Table 2.
There were significant differences between regions in the prevalence of snoring, mouth breathing, and restless sleep, all higher in the city area (Table 3). Snoring prevalence was 7.7% in the city area, 5.4% in the plains area, and 4.1% in the mountain area (P = .004, city versus plains; P > .001, city versus mountain); the prevalence of mouth breathing was 5.4% in the city area, 3.8% in the plains area, and 3.3% in the mountain area (P = .016. city versus plains; P = .001, city versus mountain); and the prevalence of restless sleep was 7.1% in the city area, 3.9% in the plains area, and 4.3 in the mountain area (P = .016, city versus plains; P = .001, city versus mountains).
In addition, there were some significant differences between boys and girls. Overall, boys had more sleep disorders than did girls (22.4% vs 19.8%; P = .013). Boys also experienced significantly more snoring (6.7% vs 4.5%; P > .001) and mouth breathing (4.7% vs 3.4%; P = .013) than did girls (Table 4).
DISCUSSION
The amount of time that people spend sleeping has decreased remarkably with technical progress and changes in lifestyle. At present, sleep duration has decreased by 20% to 25%; however, no significant effects of this decrease on growth, overall health, or lifespan have been seen.3 In our survey, the average daily sleep duration of children 2 to 5 years old was 1 hour shorter than that reported in the Nelson Textbook of Pediatrics,4 demonstrating that insufficient sleep is very common among young children.
Our study showed that the overall prevalence of sleep disorders among children in the Beijing area (21.2%) was similar to that in Western countries (20–25%),5 suggesting that childhood sleep disturbance is very common in Beijing.
The prevalence of sleep disorders in children is related to age, and the occurrence of symptoms is related to stages of physical development. Between 3 and 10 years of age, most children are developing permanent teeth. Growth of the teeth and stimulation of sprouting teeth may cause bruxism during this period.
our research, we found that the prevalence of snoring, mouth breathing, and restless sleep is higher in the city than in the rural area, which is probably because of living conditions, economics, culture, educational level of parents, and other factors. Additional research is necessary to determine the exact causes.
CONCLUSIONS
Childhood sleep disorders are very common in Beijing. Additional research is necessary to clarify the correlates between sleep disorders and age, gender, feeding, geographical location, and physical diseases. The causes and effects of insufficient sleep in young children should be investigated to improve the quality of children's sleep.
FOOTNOTES
Accepted Aug 5, 2004.
No conflict of interest declared.
REFERENCES
Liu X, Lin C, Xue Q, Qian Q. Child Health Care. Nanjing, China: Jiangsu Science and Technique Press; 1989:101
Dahl RE. The impact of inadequate sleep on children' s daytime cognitive function. Semin Pediatr Neurol. 1996;3 :44 –50
You G, Zhu S, Zhang K. Insomnia and sleep disordered disease. People’s Army Med Press. 1999:30
Richard EB, Robert MK, Hal BJ. Growth and development. In: Richard EB, Robert MK, Hal BJ, eds. Nelson Textbook of Pediatrics. 16th ed. Philadelphia, PA: W. B. Saunders Co; 2000:32 –36
Mindell JA, Owens JA, Carskadon MA. Developmental features of sleep. Child Adolesc Psychiatr Clin N Am. 1999;8 :695 –725(Xicheng Liu, MD, Yuyan Ma)