A descriptive study of sleep disorders and their impact in 2 selected schools in a divisional city of Bangladesh

Background: Sleep disorders are common in children and adolescents and have an important negative impact on their quality of life. Objective: This study was done to estimate the prevalence of sleep problems in 2 selected schools in a divisional city of Bangladesh and to evaluate the impact of sleep disorders on school performance. Method: One thousand school children between 5 to 16 years of age from the two largest schools (one boys’ and one girls’ school) were randomly selected for this study from July to December 2011. A two step procedure involved self-administered questionnaire and direct interview of the affected children and parents. The questionnaire was based on diagnostic criteria for category based classification by American Academy of Sleep Medicine. Academic performance was evaluated on the basis of cumulative results of term examinations throughout the year. Results: A total of 713 (71.3%) questionnaires were eventually returned. Of the children, 353 were boys and 360 were girls. Three hundred and ninety two sleep problems were noted in 202 (28.3%) school children and mean (SD) age of sufferer was 139 (32) months. Among the primary sleep problems, parasomnia (47.8%) was highest followed by dyssomnia (9.5%). Prominent disorders under parasomnia were nightmares (7.4%), nocturnal enuresis (4.1%) and sleep terror (3.4%) and that under dyssomnia was obstructive sleep apnoea (3.6%). School performance was significantly poor in the children with sleep disorders (p<0.001). Parasomnias were much higher in girls than boys (p<0.001). Only 20 (10.8%) parents consulted a physician for primary disorder. ________________________________________ Professor, Assistant Professor, Assistant Registrar, Department of Paediatrics, Khulna Medical College & Hospital, Khulna, Bangladesh (Received on 5 March 2014: Accepted after revision on 25 April 2014) Conclusions: In the 2 selected schools in Khulna city of Bangladesh 28.3% had sleep problems. Sleep disorders had a significant negative impact on school performance. (


Introduction
Sleep quality among children is directly related to physical health, development of intelligence and emotional growth 1,2 .Sleep-wake disorders are common and have an impact on the quality of life of children but if they are promptly recognized and treated, the outcome is favourable 3 .Insufficient quantity and poor quality of sleep in children and adolescents result in excessive daytime sleepiness which often manifests as mood disturbances, hyperactivity, poor impulse control and neurocognitive dysfunction 4,5 .Lack of community awareness of the negative effect of sleep problems also contributes to under reporting of parents at medical consultation [6][7][8] .
Studies of children and adolescents in the general population have indicated that 20-30% have sleep problems of concern to parents 4 .Three general categories of sleep disorder are: initiating and maintaining sleep (dyssomnia), sleep-wake transition disorder (parasomnia) and arousal disorders [9][10][11] .Mindell and Adair emphasized two major groups: dyssomnias and parasomnias 12,13 .American Academy of Sleep Medicine (AASM) has described over 80 problems in the International Classification of Sleep Disorders 14 .This widely accepted classification has two principal groups: primary disorders related entirely to sleep and secondary disorders related to other physical conditions.
Most of the available reports on sleep disorders are mainly focused on preschool children and are reported to be higher in young children and males 15 .However, sleep disorders in school children have rarely been evaluated and might be different from those in preschool children in magnitude, nature and aetiology 16 .

Objectives
• To estimate the prevalence of sleep disorders in 2 selected schools in a divisional city of Bangladesh.
• To evaluate the impact of sleep disorders on school performance.

Method
Sleep disorders were studied in 2 selected schools in Khulna, a divisional city of Bangladesh.Most large scale surveys on child health problems are based on parental perception 16 .This cross sectional observational study was done in two steps as per design of Guilleminault and colleagues: selfadministered questionnaire and direct interview of the affected children and parents to minimize the weakness of recall bias and diagnostic confusion 17 .
Students from each class were randomly selected for enrolment as study cases.Parents of the selected students and the school teachers were invited to a meeting to explain the purpose of the study.Questionnaires were handed over to the parents and guidelines were given on how to fill up the questionnaire along with the characteristics of 20 different sleep problems as included in the format.Children who did not return the questionnaire within two weeks were sent a reminder through the class teacher to maximize the response.In the second step, parents of children having sleep problems were invited to the Sleep Clinic in our hospital for a clinical interview.Elaborate history was reviewed and physical examination of the student was performed by the researchers to crosscheck the information in the questionnaire.A few mothers who failed to attend the clinic were interviewed over the telephone.The diagnosis of the sleep disorders under six categories was based on the criteria set by AASM 14 .A problem being potentially dangerous to life or causing severe disruption to normal activities was considered as a major disorder 18 .
The questionnaire was adapted from validated 'sleep disturbance scale' developed in Rome and applied as survey questionnaire by sleep centre of Sydney Children's Hospital 18,19 .The questionnaire was translated into local language (Bangla) and tailored for appropriateness in the target group.In a self-administered questionnaire, parents were asked if their child had disturbed sleep at night excluding periods of illness.Apart from general information, questionnaire consisted of 20 items, one for each of the sleep disorders viz.Choking/gasping, abnormal leg movement, walking, frighten and forget, paralysis, bed wetting, irresistible sleep, breathing difficulty, panic attack and convulsions.The parents had to tick one of the alternatives that best fitted with their child's condition.The alternatives were: yes/ no/ not known.Parents were also asked if they had consulted a doctor in the last 12 months about their child's difficulty in sleeping.Academic performance was measured on the basis of cumulative results of term examinations in respective class throughout the year.Socioeconomy was considered on monthly family income and income of Tk. 10,000-20,000 was taken as middle class and the higher or lower figure were considered accordingly.Underlying medical conditions were included only when diagnosed by a medical specialist.
A test-retest reliability of the questionnaire was conducted at an interval of one week by distributing the questionnaire among a small group (30) of parents who have a school going child.Response to these questions was verified and questionnaire was revised to make it easily and uniformly comprehensible to the parents.Two investigators were recruited for the survey and they were also trained to explain the questions in a uniform manner to ensure quality and consistency of finding.A forwarding letter along with the questionnaire included a brief description of the study and written informed consent was obtained from each parent.The study was approved by the Ethical Review Committee of Khulna Medical College and Hospital.
Data from questionnaire and interview were cleaned and checked for validity.They were coded and entered in the Statistical Program for Social Science (SPSS version 12, SPSS Inc., Chicago) for analysis.For continuous variable mean, standard deviation and range were calculated.Chi-Square test was done for categorical variable to find out the significance.In all tests p value below 0.05 was considered as significant.

Results
A total of 1000 questionnaires were randomly distributed among the 6000 school children, half in the girls' school and the other half in boys' school.Initial return was around 55% but after first and second reminder, 353 (71%) questionnaires were eventually returned from boys' school and 360 (72%) from girls' school.Thus the total study population became 713 (71.3%) between 5 to 16 years and the male: female ratio was 1:1.02.Sleep disorders (392) were noted in 202 (28.3%) children with multiple problems.Boys and girls ratio of affected children was 1:1.1 and the mean (SD) age of the sufferer was 139 (32) months ranging from a minimum of 63 to a maximum of 198 months.Majority (43.1%) of children belonged to middle class family and a small portion (25.8%) came from low socioeconomy.Primary sleep disturbances (235; 60%) were much more common than the secondary disturbances (157; 40%) as shown in Table 1.Among the primary disturbances parasomnias (187) were the highest followed by dyssomnias (37) and hypersomnias (11).Prominent disturbance under dyssomnia was obstructive sleep apnoea (3.6%).Prominent disturbances under parasomnia were nightmares (7.4%), nocturnal enuresis (4.1%) and sleep terror (3.4%).Secondary sleep disturbances were frequently associated with mental disease such as post traumatic stress disorder (7%) and neurologic disease such as arousal headache (6%) but medical diseases such as sleep asthma (2.8%) were noticed in a small number of children.

Table 1: Prevalence of sleep disturbance in school children
School performances of the affected children were compared with that of normal children on the basis of term examination result (Table 2).3).On the other hand, most of the sleep categories, when compared individually, were significantly higher in female children than male, particularly parasomnia (p<0.001) but dyssomnias and problems secondary to medical diseases were higher in male children.

Discussion
Sleep disturbances in the present study were noted in 28.3% children with overlapping problems (1.9 problems per child).Frequently encountered primary disorders were nightmares (7.4%), nocturnal enuresis (4.1%), obstructive sleep apnoea syndrome (3.6%) and sleep terror (3.4%).In Great Britain, sleep problems of varied nature and intensity affect 20% children at 5 years, 6% at 11 and less than 1% children had serious problems from age 9 onwards 16 .The decline in sleep problems with age provides indirect evidence that these problems have a good prognosis but several researchers reported that sleep problems persist in a subgroup of children 11,16 .Studies in Belgium, Sweden, New Zealand and Spain have reported current sleep problems between 33% to 46%, well above the prevalence study in Britain, although part of the discrepancy may be due to use of different questions to ascertain sleep problems 12,13,20 .
The overall prevalence of sleep disorder in Beijing was 21.2% and was similar to that in western countries (20-25%)  4,24 .In Britain, parents of severe cases of sleep disorder are reluctant to ask for medical help because they think health service cannot help in this area 16 .Similarly, our study parents were also concerned about sleep disorders in children but they did not consider it as a medical problem to share with the physicians.However, treatment of sleep disturbance in school children might help in improvement of school performances.
In this study, proportion of over-10 year sufferers (29.7%) was higher than under-10 (25.8%) and proportion of affected children among girls (30%) was more than the boys (26.6%) but none of the differences were statistically significant.However, considering the number of problems, most (4/6) of sleep categories were significantly higher in girls.
In fact, prevalence of sleep disorder in children is related to age and stage of physical development 25,26 .In China, boys had more sleep disorders than girls (22.4% vs. 19.8%;p=0.013) and the prevalence of bruxism was significantly higher in preschool (8.5%) than school (3.7%) children 1 .In Australia, sleep disorder persisted across the whole range (4-16 years) showing only small age related decrease and apart from sleep related hyperhydrosis, no strong gender difference was found 15,27 .Our observation regarding age was nearly similar, but regarding gender, parasomnia was remarkably higher in girls, which might be related to insecurity in our society.
The principal limitation of the present study was the identification of sleep disturbances on questionnaires and direct interview without polysomnography due to lack of facilities.Other limitations were a sample of convenience, reliance on parental recall report and their limited awareness of the potential consequences of the sleep problem on the children and families.Several confounding factors influence the school performance besides sleep disorder, which was beyond the scope of present paper.

Conclusions
• In the 2 selected schools in Khulna city of Bangladesh 28.3% had sleep problems.
• Sleep disorders had a significant negative impact on school performance.
Further large scale studies can be done to evaluate the national picture.There is also a need for increased awareness of sleep problems in the community which should be properly addressed at consultation due to its impact on children and families.

Table 2 : School performance in relation to sleep status
Categories of sleep disturbances were divided into two different age groups: under-10 years (248) and over-10 years (465) of age (Table

Table 4 : Gender difference in sleep disturbance
* Chi Square test