sleep disorders are very common in children , but due to their varying presentations , their incidence as behavioral , learning , and mental - behavioral problems can not usually be diagnosed . sleep patterns change throughout life , although the quality and quantity of sleep always depend on individual factors such as age , sex , and psychological and environmental factors ( 1 ) . in children quantitative sleep problems such as disorders in sleep onset and qualitative sleep disorders such as frequent awakenings may lead to insufficient sleep ( 3 ) . inadequate sleep symptoms and complications in children are different from those of adults and may reveal themselves as changes in mood , activities , and excessively shortened attention span and neurological cognitive disorders such as inattention . sleep disorders in children not only affect their health and hygiene , but can also be an important factor for causing stress , pressure , and tension in the family , and even cognitive disorders in adolescence ( 4 ) . information on sleep disorders in children is an important factor influencing their growth and development ( 5 ) . sleep is an organized behavior that is repeated every day as a vital necessity based on biological rhythm , but its exact mechanism is not known . chemical , vascular , and hormonal theories have been suggested in regards to sleep ( 2 ) . people need different amounts of sleep depending on a variety of factors such as age , genetics , and their physical and mental states ( 6 ) . at 6 weeks of age , children need about 14 - 16 hours of sleep ; by one year of age , they require 12 - 24 hours ; during the second year of age , the number of hours needed is reduced somewhat , reaching almost 12 hours a day ; and the sleep characteristics of three - year - old children are similar to those of adults ( 7 ) . there are different views on the onset of sleep disorders in childhood according to study groups and health care providers . the prevalence of sleep disorders has been reported as 10% - 30% in primary care and up to 37% in sleep centers ( 8) . establishing a healthy sleep pattern in children requires parents information and cooperation . therefore , at each visit for growth monitoring , the parents should be questioned regarding their child s sleep patterns , and they must pay attention to the development of a proper sleep pattern just as they support good nutrition and oral hygiene ( 9 ) . the prevalence of sleep disorders in children encompasses a wide range and has been reported from 15% to 86% ( 10 ) . goldman reported the prevalence of sleep disorders as 33% ( 11 ) . in a study by rzepecka , the prevalence of sleep disorders was reported as 42% ( 12 ) . in iran , the prevalence of sleep disorders was reported as 41.6% ( 13 ) , 30.9% ( 14 ) , and 50.4% ( 15 ) . ebarhim et al . found that the most common sleep problem in children was daytime sleepiness ( 16 ) . some factors that affect sleep include socioeconomic conditions , drug side effects , psychological factors such as parental distress , environmental factors such as sleep environment , sleep patterns representing social - cultural differences that govern the communities , and children s interactions with their parents ( 17 ) . the high prevalence of sleep disorders in children indicates the considerable importance of addressing them in preschool - aged children ; unfortunately , they are not addressed sufficiently in children care . the most serious complication related to sleep disorders in children is cognitive problems , which place children at risk for educational failure , family problems , and social psychological problems ( 18 ) . the purpose of this study was to assess the prevalence of sleep disorders among 4- to 6-year - old children attending the health centers of shahid beheshti university of medical sciences , tehran , iran , in 2013 . this cross - sectional study was conducted on 400 children from december 2012 to may 2013 . the area of health care centers related to shahid beheshti university of medical sciences in tehran was divided into four geographical classes : north , south , west , and east . two centers were chosen from each class , and 400 children from these centers were randomly selected . after explaining the study objectives , if their children met the study inclusion criteria , informed consents were obtained from the children s mothers . the questionnaires were filled out through interviews with each child s mother . the sample size was calculated according to this formula : p * ( 1 - p ) * ( z ( alpha/2 ) + z ( beta ) ) ^ 2/epsilon ^ 2 = 384 ( 19 ) . children with chronic disease ( n = 8) , mental disability ( n = 5 ) , or who used sleep drugs ( n = 7 ) were excluded . in total , 400 children participated ( figure 1 ) . this study was approved by the ethics committee of shahid beheshti university of medical sciences ( no : 91 - 01 - 43 - 61331 - 1 , dated : 2012/03/18 ) . after obtaining permission from the authorities of the shahid beheshti university of medical sciences , the authors approached the parents of qualified children . the objectives of the study were explained , written informed consent was obtained , and the parents participated in the study in a private setting . the parents were assured that all of their information would be kept confidential and that they did not need to mention their names on the questionnaires . all ethical issues - informed consent , conflicts of interest , plagiarism , misconduct , data fabrication and/or falsification , double publication and/or submission , redundancy , etc . have been considered carefully by the authors . the inclusion criteria were : being iranian ; not having chronic diseases or mental , physical , or mental disability ; not using sleep drugs ; and lack of known parental mental and physical diseases . the data collection tools were the children s sleep habits questionnaire ( cshq ) containing 50 items , and the questionnaire for the demographics of the women and their husb parents and children ands containing 37 items . the cshq ( standard ) is designed in likert style , with each item rated on a three - point scale : 1 = rarely ( 0 - 1 time per week ) ; 2 = sometimes ( 2 - 4 times per week ) ; and 3 = usually ( 5 - 7 times per week ) . a total score of greater than 41 is the cutoff for diagnosing sleep disturbances in children . sleep disturbances included bedtime resistance , sleep onset delay , sleep duration , sleep anxiety , awakening during the night , parasomnias , sleep - related breathing disorders , and daytime sleepiness . in iran , the cshq was used in the study by shoghy et al . ; they reported on its reliability using the test - retest method ( r = 0.97 ) ( 20 ) . wang et al . assessed the cshq using the content validity method , and cronbach s alpha coefficient of the cshq was 0.80 ( 21 ) . cronbach s alpha coefficient of the cshq was found in a previous study to also be 0.80 ( 12 ) . in this study , the cshq was validated through content validity . for internal consistency of the cshq , cronbach s alpha coefficient for the total scale was 0.82 and its reliability was measured by test - retest with a 10-day interval ( r = 0.95 ) . data were analyzed with the statistical package software for social science , version 16 ( spss , inc . , the normality of the data was evaluated by the one - sample kolmogorov - smirnov test ( p > 0.05 ) and the homogeneity of variances was evaluated by the leven test ( p > 0.05 ) . frequency , percentage , and mean standard deviation were used to describe the characteristics of the children and the prevalence of sleep disorders . for the relationship between the quantitative variables of sleep disorders - age and body mass index - the pearson test was used . the t test was used for the relationship between the binary variables of sleep disorders . ( after checking anova assumptions ) , the relationship among the third and fourth groups sleep disorders and father s job , that over two groups was analyzed by anova . ) .logistic regression was also used for the strength of the relationship . for all of the statistical tests , a p value of less than 0.05 was considered significant . children had favorable weight ( 98.25% ) , head circumference ( 99.75% ) , and developmental condition ( 100% ) . the mothers mean age was 31.06  5.14 years and the fathers mean age was 36.55  1.85 years . most mothers were housewives ( 87.25% ) , many were university educated ( 40.5% ) , did not smoke ( 98.5% ) , and did not use opium ( 100% ) . some had physical diseases ( 12.5% ) and used drugs ( 7.5% ) . the mean bedtime for children was 9:51 pm ( sd = 3 hours and 58 minutes ) ; the mean duration of sleep was 9 hours and 8 minutes ( sd = 3hours and 9 minutes ) . sleep disorders were significantly associated with children s age , height , and body mass index ( bmi ) , mother s diseases , father s drug abuse , and the level of satisfaction of the parents sexual relationship ( p < 0.05 ) ( see table 3 ) . anova showed that sleep disorders were significantly associated with the father s job ( p = 0.016 ) . the tukey s test ( post - test ) showed that the mean scores for sleep disorders in children whose fathers worked were higher than the mean scores in children whose fathers had private jobs ( p = 0.10 ) . sleep disorders were significantly associated with the children s residence ( p = 0.011 ) . the tukey s test ( post - test ) showed that the mean scores for sleep disorders in children who lived in tenant housing were higher than the mean scores in children who lived in private houses ( p = 0.042 ) . logistic regression was used for the relationship between sleep disorders and the variables ( see table 4 ) . the authors found the prevalence of sleep disorders in the studied population to be 36.25% . wang et al . reported the prevalence of sleep disorders in children to be 69.3% ( 21 ) , which is higher than that of our study . ardani et al . found the prevalence of sleep disorders in children to be 39.8% ( 22 ) . day et al . found the prevalence of sleep disorders in children to be 43.5% ( 23 ) . jan et al . reported the prevalence of sleep disorders to be 25 - 40% ( 24 ) . these differences in the prevalence of sleep disorders can be attributed to differences in the study populations and the use of different tools for data gathering ( 13 ) . sleep disorders can cause fatigue , lethargy , depression , negative moods , and dysfunction ( 25 ) . sleeping habits and the quality and quantity of sleep affect childhood health . learning bad habits can affect adulthood health and endangers individual and public health ( 26 ) . sleep problems can cause anxiety , reduced adaptation rate , and low self - esteem in children ( 27 ) . the persistence of these problems is associated with alcohol and drug abuse in adulthood ( 28 ) . showed a positive significant association between sleep disorders and children s age ( 20 ) . in contrast , liu et al . found a significant association between bedtime resistance and children s age ( 29 ) , but gharamaleki et al . did not find a significant association between sleep quality and children s age ( 30 ) . in our study , children s height and bmi had a significant association with sleep disorders . bagley et al . also showed a significant association between sleep quality and bmi ( 32 ) . late - night feeding may lead to sleep disorders because increased fluid intake leads to increased urination , which can lead to more severe insomnia . some childhood diseases such as diabetes whose symptoms develop at night may lead to sleep disorders in children . inadequate sleep can compromise the immune system s function , hormonal function , and cause other health - related consequences ( 34 ) . other studies have also acknowledged the impact of chronic illness on children s sleep ( 24 , 35 ) . although the mechanism is not clear , one hypothesis is that frequent insufficient sleep may change the hormones leptin and ghrelin periodically , which would result in increased hunger and desire to eat food ( 36 ) . another study claimed there was a possibility that shortening sleep duration put children at risk for diabetes ( 37 ) . the present study did not find a significant association between sleep disorders and the father s job and level of education . however , shoghy et al . found a significant association between sleep disorders and the father s level of education ( 20 ) , and sadeh et al . showed that when a father s education level increased , the children s sleep problems decreased ( 38 ) , although the reason is not clear . scientists believe that perhaps this is a result of discipline in such families or better knowledge of educated parents about sleep problems and child - rearing ( 39 ) . furthermore , it seems that increased awareness of educated parents and intimate interactions with their children that lead to a discharge of emotions and lower psychological pressure will cause improved quality of sleep . we did not find a significant association between sleep disorders and having a separate room , but mohammadi et al . reported a significant association between sleep disorders and having a separate room ( 18 ) . in contrast , panaghi et al . also did not find this relationship ( 13 ) . they showed that 63.8% of children slept in separate rooms , 10.1% shared a room , and 26.2% shared a bed with their parents ( 21 ) . for children , socioeconomic status is associated with sleep and insomnia duration ( 40 ) . living conditions in less developed urban areas , with poor hygiene , poverty , and low income , can lead to sleep disorders ( 41 ) . unfortunately , there is no health guarantee factor for millions of children because they suffer from a lack of health promotion services . changes in modern society including the progress of medical awareness and technology , increased urbanization , economic changes , and other changes that will lead to lifestyle changes are factors affecting children s health . recent studies have a greater focus on children because they have the highest level of risk ( 41 ) . the amount of alcohol and cigarette use and other risky behaviors were greater in parents who had children with sleep disorders . this can be attributed to parents stress , since one way to release it is to turn to cigarettes , alcohol , and drugs , as is discussed in other research ( 43 ) . lack of attention or neglectfulness by their parents can lead to the development of anxiety , tension , and fear in children ( 23 ) . we observed a significant association between sleep disorders and marital satisfaction . in a study by shoghi et al . , there was a significant relationship between the number of disputes between parents and sleep disorders in children ( 20 ) . showed that an increase in arguments between parents led to increased nocturnal awakenings in children ( 38 ) . researchers have reported that poor quality of sleep can be due to decreased marital satisfaction ( 44 ) . marital distress and family conflict that is caused by poor interactions between the parents can be a predisposing factor for psychological problems that ultimately show themselves as sleep disorders . marital disputes can have harmful effects on the safety of the home environment and can lead to children s restlessness , bad temperament , not eating , seclusion , and not participating in social games ( 45 ) . marital disputes and conflicts can cause reduced child safety in the home environment , failure or instability in parent - child communications , unsustainable practices , reduced parental monitoring , and aggression in children that requires intervention . it can even influence the addition of other environmental stress factors , such as friendship with peers with high - risk behaviors ( 46 ) . quality of sleep is one aspect of living well and has a strong relationship with quality of life , satisfaction with life , stress hormones , and cortisol levels ( 47 ) . quality of sleep in children is an important predicting factor for the mother s quality of sleep , which can affect her daily activities ( 6 ) . a study showed that there was a significant relationship between children s interactions and parents moods . sleep - related behaviors are not only shaped by biological and developmental factors but also by socio - cultural contexts including social values , social norms , and parents behaviors ( 48 ) . cultural differences may affect the place , time , and quality of children s sleep ( 49 ) . in the usa , pediatricians recommend that children sleep alone in their own bed at bedtime , which is a reflection of social factors on individual self - efficacy ( 50 ) . most often , children follow their parents behavioral patterns like staying awake and watching tv in bed ( 51 ) . an increase in irregular sleep habits of parents and delays in their sleep will lead to an increase of bad sleep habits in their children . behaviors such as self - dominance , self - control , stability , and parents taking responsibility are effective for correcting children s behaviors , and usually parents positive emotional responses would result in children s peace - of - mind ( 52 ) . parents with psychiatric disorders spend less time with their children , affect them less , and monitor them very little . they often use more severe punishments and less encouragement and are not flexible in their opinions ( 53 ) . in short , a lot of emotional frustrations in children are associated with their sleep patterns ( 31 ) . sleep is a window into the social , familial , and emotional performance of every person . training sessions on the importance of getting enough and high quality sleep should be held in health centers and proper strategies for sleep should be provided to stressful families with low literacy . sleep disorders should be considered in the differential diagnosis of children s learning and behavioral problems . one limitation of this study was that the information about sleep disorders was obtained from the children s mothers and they may not be aware of sleep disorders in their children . some mothers refused to talk about diseases they , their spouse , or their children had . one of strong points of this study was the assessment of the prevalence of sleep disorders in iranian preschool children . the authors found there was a socioeconomic status relationship with sleep disorders . against this strength , this study was conducted in tehran province , so may not reflect the general population of iran . sleep is a window into the social , familial , and emotional performance of every person . training sessions on the importance of getting enough and high quality sleep should be held in health centers and proper strategies for sleep should be provided to stressful families with low literacy . sleep disorders should be considered in the differential diagnosis of children s learning and behavioral problems . one limitation of this study was that the information about sleep disorders was obtained from the children s mothers and they may not be aware of sleep disorders in their children . some mothers refused to talk about diseases they , their spouse , or their children had . one of strong points of this study was the assessment of the prevalence of sleep disorders in iranian preschool children . the authors found there was a socioeconomic status relationship with sleep disorders . against this strength , this study was conducted in tehran province , so may not reflect the general population of iran .
backgroundsleep patterns may change over a person s lifetime ; however , the quantity and quality of sleep always depend on individual factors such as age , sex , and psychological and environmental factors . in children 
 , sleep is as important as development . 
 quantitative sleep problems related to sleep onset and qualitative sleep disorders such as frequent awakenings may lead to insufficient sleep.objectivesthis study aimed to assess the prevalence of sleep disorders among children 4 - 6 years old attending the health centers of shahid beheshti university of medical sciences , tehran , iran , in 2013.patients and methodsthis was a cross - sectional study on 400 children selected using a multistage sampling method . 
 data were collected by interviews . 
 the questionnaire included two sections : a demographic section with questions about the demographic characteristics of the children and parents and a children s sleep habit questionnaire ( cshq ) . 
 data were analyzed by spss 16 and different statistical tests were used ( p < 0.05).resultsthe mean age of the children was 64.27  9.3 months . 
 the prevalence of sleep disorders was 36.25% . 
 sleep disorders were significantly associated with age , height , body mass index , residence of children , father s occupation , mother s diseases , father s drug abuse , and parents marital status ( p < 0.05).conclusionssleep disorders in children threaten growth and development , and are dangerous for their health . 
 sleep disorders should be considered in the differential diagnosis of children s learning and behavioral problems .