Sleep patterns and sleep disorders in children with autistic spectrum disorders: insights using parent report and actigraphy

Sleep patterns and sleep disorders in children with autistic spectrum disorders: insights using parent report and actigraphy Luci Wiggs* BSc DPhil; Gr...
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Sleep patterns and sleep disorders in children with autistic spectrum disorders: insights using parent report and actigraphy Luci Wiggs* BSc DPhil; Gregory Stores MA MD FRCP FRCPsych, University of Oxford Department of Psychiatry, Oxford, UK. *Correspondence to first author at University of Oxford Section of Child and Adolescent Psychiatry, Park Hospital for Children, Old Road, Headington, Oxford, OX3 7LQ, UK. E-mail: [email protected]

The present study sought to describe the profile of sleep disturbance reported in children with autistic spectrum disorders (ASDs) and to document any sleep disorders underlying reports of sleeplessness. Sixty-nine children aged 5 to 16 years (mean 9 years 4 months, SD 2 years 7 months; 14 females) with an ASD were assessed by detailed sleep histories taken from parents, the Simonds and Parraga Sleep Questionnaire, a 2-week sleep diary, and actigraphs worn by the child for five nights. Parent-reported sleeplessness featured prominently (64%). Sleep disorders underlying the sleeplessness were most commonly behavioural (i.e. to do with inappropriate sleep-related behaviours), although sleepwake cycle disorders and anxiety-related problems were also seen. In addition, the sleeplessness patterns of a large minority of children could not be classified by conventional diagnostic criteria. Sleep patterns measured objectively did not differ between those children with or without reported sleeplessness, but the sleep quality of all children seemed to be compromised compared with normal values.

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Severe sleep problems are reported in most children with autistic spectrum disorders (ASDs). Various aspects of sleeplessness (extreme difficulty getting to sleep, long periods of night waking, short duration sleep at night, early morning waking and consequent daytime sleepiness) are consistently the most commonly reported (reviewed in Stores and Wiggs 1998; Richdale 1999, 2001). Other types of disturbed sleep have received less attention but certain parasomnias (episodes of disturbed behaviour during sleep) have been reported to occur more frequently in children with ASDs than in other various groups (DeMeyer 1979, Schreck and Mulick 2000), although other studies report no increased rate of parasomnias (Richdale and Prior 1995, Patzold et al. 1998). Inconsistencies are perhaps unsurprising because the literature on sleep problems in children with ASDs is limited, not only in quantity but also in quality, in that reports frequently contain shortcomings that prevent firm conclusions from being drawn. Major difficulties in comparing results are changes in diagnostic criteria for autism over time, poor control for (or at least description of) relevant factors (including associated medical conditions) affecting sleep, and variable assessment and documentation of sleep and its disorders (Stores and Wiggs 1998). When objective measures of sleep have been examined, apparently non-specific abnormalities in detailed sleep architecture have been inconsistently identified (see Stores and Wiggs 1998). It is interesting that the one study comparing parent report of sleep problems in children with ASDs with an objective documentation of sleep patterns (Hering et al. 1999) failed to find objective evidence of disruption apart from confirming that the children with ASDs woke earlier in the morning. The authors suggest that the parents of such children might be biased in their reporting, although methodological limitations of the study could be another explanation. There is certainly a need for more studies to examine the matter of correspondence between parent report and objective sleep disruption. One can conclude that the available literature highlights sleep problems, of one sort or another, as being common and serious but without sufficient detail to allow adequate guidance for choice of treatment. This is because an important distinction should be made between sleep problems (the presenting pattern of sleep disturbance) and the underlying sleep disorders giving rise to those disturbed patterns. Whereas there are three main types of presenting sleep problem (sleeplessness, excessive sleepiness, and parasomnias), there are over 80 different sleep disorders listed in the International Classification of Sleep Disorders – Revised (American Sleep Disorders Association 1997) that could be the underlying cause of the sleep problem. Identifying sleep disorders, rather than problems, has important practical consequences because the choice of treatment needs to be based on the individual’s sleep disorder, not simply the presenting symptoms. As an illustration, the sleep problem of ‘sleeplessness’ might be caused by sleep disorders related to behavioural matters, anxiety or, for example, circadian rhythm abnormalities; different approaches to treatment would be required for these various underlying causes. Thirumalai et al. (2002) presented the polysomnographic findings of a series of 11 children with autism whose parents complained of ‘frequent nocturnal awakenings’ and identified rapid eye movement sleep behaviour disorder (which typically most commonly affects elderly males with neurodegenerative disease) in five

of 11 children. Appropriate intervention (namely clonazepam or carbamazepine) successfully controlled the sleep disorder, illustrating the need for careful assessment and treatment of the disorder underlying any sleep abnormalities. Effective treatment is important, not only because sleep disorders are distressing to the child and the family at the time that they actually occur, but also because there is good evidence that persistent sleep disturbance has a harmful effect on the child’s learning and behaviour in several ways (Stores and Wiggs 2001). This is a particularly serious matter for children who are already compromised in these areas. Further, children’s sleep disorders are associated with increased rates of family difficulties, such as maternal ill health, marital discord, and impaired parent–child relationships including the use of physical punishment and, possibly, abuse in extreme circumstances (Chavin and Tinson 1980; Richman 1981; Quine 1991, 1992). Fortunately there have been studies suggesting that successful treatment of the child’s sleep problem reduces or resolves some of these associated negative factors (Quine 1992, Wolfson et al. 1992, Minde et al. 1994, Wiggs and Stores 2001). Given the high rates of reported sleep problems in children with ASDs and the negative associations between childhood sleep problems and child and family function, it is of practical importance to investigate ways of treating sleep problems in children with ASDs. However, to evaluate the effectiveness of treatments for sleep disorders in children with ASDs, the types of sleep disorder to which they are prone need to be ascertained so that appropriate interventions, likely to affect the largest number of children, can be examined. There are case reports suggesting that a variety of approaches can be useful (Richdale 2001) although, as pointed out by Schreck (2001) there is a need for high-quality data upon which management guidelines can be based. There are also worrying indications that the treatment needs of children with sleep disorders and special needs are not being met adequately (Wiggs and Stores 1996a). Improving understanding on the part of parents and professionals is an important step towards increasing the number of children who receive appropriate help. The current study, therefore, had the following aims. (1) To investigate the wide range of possible sleep disturbance and to describe the profile of reported sleep disturbance in a group of children with ASDs. (2) To describe the nature and extent of sleep disorders underlying sleeplessness (because it seems to be the most commonly reported sleep problem) in a group of children with ASDs, in order to indicate the type of help needed for such children, including suggesting which specific interventions should be the focus of future controlled investigations. (3) To document the objective sleep disturbance associated with parental reports of sleeplessness in view of the inconsistent correspondence reported in the literature between subjective and objective assessment. The investigation was given full approval by the local research ethics committee, and informed consent was obtained from the parents (and children where appropriate). Methods PARTICIPANTS

Letters of invitation to participate were sent, with reply slips and freepost envelopes, to 144 consecutive eligible families identified via the Oxfordshire Education Autism Support Service and the Oxfordshire Parent Support Group for Autism.

Children associated with these services have been diagnosed by psychiatrists, paediatricians, and clinical psychologists according to ICD-10 criteria (International Classification of Diseases; World Health Organization 1992). Criteria for eligibility were being aged between 5 and 16 years, and living in the Oxfordshire area. Reminder letters were sent to non-responders after 1 month. A total of 108 replies were received: 67 families (two of the families had two eligible children; thus 69 children in total) agreed to participate, and 28 decided not to participate (no reasons for non-participation were offered); thirteen were not eligible (three outside age range, 10 living outside the catchment area). In total, 70 children were recruited into the study but the results are based on 69 children because, on enquiry, one child was found not be eligible as the family had moved out of the catchment area for study recruitment. The final sample comprised 69 children ages 5 to 16 years (mean 9 years 4 months, SD 2 years 7 months; 14 females) with an ASD. ASSESSMENTS

Basic descriptive information A structured interview was used to gather information about the following: (1) demographic information; (2) the child’s health (including developmental history, any medications being taken, current and past physical or psychiatric problems including epilepsy); (3) intellectual level classified broadly according to the type of school placement: mainstream school, highest functioning children (i.e. generally without intellectual impairment); educational unit, middle functioning group (i.e. mild intellectual impairment or behavioural difficulties that necessitate attending a special educational unit for autistic children attached to mainstream school, many being slowly integrated into mainstream); and special school, lowest functioning children with intellectual impairment (moderate and severe); (4) family medical history; (5) matters relating to autism (e.g. diagnosis and by whom, age of child at time of diagnosis, specific treatments tried in the past). Sleep Objective and subjective measures of sleep patterns were made. Sleep history. A detailed sleep history, based on the child’s 24-hour sleep–wake patterns, was taken from the parents (Stores 1996). As part of this assessment, parents were asked ‘In your opinion does your child currently have a sleep problem?’ and ‘In your opinion has your child had a sleep problem in the past?’ If they answered yes to either of these questions they were asked to describe the problem in detail. To gather more systematic information about a wide range of sleep disorders the history-taking schedule included verbally administering the Simonds and Parraga Sleep Questionnaire (Simonds and Parraga 1982). The questionnaire covers a wide range of sleep disturbances. Part one of the questionnaire is concerned with the quantity and quality of the child’s sleep. Items require yes/no answers or a reply in hours (e.g. ‘Does your child generally sleep soundly?’, ‘How many hours does your child sleep?’). Part two of the questionnaire is concerned with identifying sleep disorders. Four broad categories of disorder are covered and expressed in plain English: disorders of initiating and maintaining sleep, parasomnias, sleep-related breathing problems, and daytime sleep-related features (i.e. drowsiness or increased activity as a possible consequence of

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sleep disturbance in children). A seven-point scale to indicate the frequency of a problem was used, so that a distinction could be made between minor and clinically significant problems. Parents were asked to rate the frequency of occurrence of the sleep-related behaviours on a scale of ‘Never’, ‘Less than once a month’, ‘About once a month’, ‘Two to four times a month’, ‘Once or twice a week’, ‘Three to six times week’, or ‘Daily’. Behaviours occurring ‘Never’, ‘Less than once a month’, ‘About once a month’, or ‘Two to four times a month’ were classed as ‘Infrequent’. A distinction was made between more frequently occurring behaviours which were classed as happening ‘Sometimes’ (‘Once or twice a week’) or ‘Often’ (‘Three to six times a week’ or ‘Daily’). On the basis of this information children were divided into two groups: those with sleeplessness and those without sleeplessness. Sleeplessness was defined as parents reporting the frequent occurrence (i.e. happening three or more times per week) of any of the items concerned with these sleep problems, namely: reluctance to go to bed; fear of going to bed; problems settling child; child taking longer than 1 hour to settle to sleep; waking in the night; insisting on sleeping with someone else; waking before 05:00 (early waking); and excessive daytime sleeping. Sleep diary. A sleep diary record was completed by parents over a 1-week period. This has been shown to provide additional useful information about a child’s sleep patterns and problems, especially parents’ attempts to deal with sleep difficulties, and has been shown to be an important adjunct to actigraphy (described below) when used to edit data and remove artefacts (Sadeh 1996). Parents recorded their child’s sleep and wake times (including daytime naps), bedtime and night-waking behaviour (of parent and child), and any other significant events that occurred by day or night. Actigraphs. The children wore actigraphs (Ambulatory Monitoring Inc, New York, USA) for five weekday nights to provide an objective recording of their sleep. Activity monitors are movement sensors, worn on the non-dominant wrist like a watch. Validated software scoring permits the identification of periods of sleep and wake (Sadeh et al. 1994). The following variables were derived for every night of recording: (1) Time at sleep onset. (2) Sleep latency (i.e. time in minutes taken to fall asleep between getting into bed to settle for sleep and time at sleep onset). (3) Time at final waking. (4) Total sleep duration (minutes). (5) Activity (percentage of minutes of the period from sleep onset to final waking with any movement). (6) Minutes of wake (total number of minutes spent awake between sleep onset and time of final waking). (7) Number of wakes after sleep onset. (8) Duration of longest wake (in minutes). (9) Sleep efficiency (percentage of time in bed between ‘lights out’ and ‘get up’ actually spent asleep). (10) Acceleration Index (index ranging from –1 to +1, with 0 representing uniform distribution of activity during sleep period, a negative value indicating slowing activity and positive values indicating an acceleration of activity during the sleep period). Data for each child were averaged over the five nights, as recommended (Acebo et al. 1999) and the averaged scores were analyzed. On the basis of this detailed assessment using both subjective and objective information, sleep disorders underlying the parent-reported sleeplessness could be diagnosed according to the diagnostic criteria defined in the International Classification of Sleep Disorders – Revised

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(American Sleep Disorders Association 1997). Other assessments Mothers also completed questionnaires to assess aspects of their child’s and their own functioning. Areas examined were: the degree and type of autistic behaviour (Krug et al. 1993), child anxiety (Einfeld and Tonge 2000), maternal sleepiness (Johns 1991), maternal mental state (Goldberg and Williams 1991), and maternal beliefs and attitudes relating to child sleep patterns (Morrell 1999). Details of these assessments and the results will provided in a separate paper (L Wiggs and G Stores, In preparation). PROCEDURE

Families agreeing to participate were contacted and an appointment was arranged to meet at the family home where the structured interview, to gather basic descriptive information and the sleep history, took place. Families were given an actigraph for the child to wear and were also provided with a sleep diary to complete. Instructions for using both of them were provided and discussed. It was suggested that if the child did not want to wear the actigraph that parents could, if they wished, try attaching the monitor after the child had fallen asleep. One week later the actigraph and sleep diary were collected from the family home. STATISTICAL ANALYSIS

Descriptive statistics were used to describe the profile of sleep disorders and sleep-related features in the group as a whole and also to compare the ASD actigraph data with normal values. A database of limited normal data on 17 children without disabilities aged 6 to 12 years is available (Action-W; Ambulatory Monitoring Inc). The software (Action-W) compares index data with the database scores and provides, among other things, the centile for each score. Centile scores are arbitrarily divided graphically into sections with scores that fall in the top (0 to 16.6%) or bottom (83.4 to 100%) sixth, indicating ‘extreme’ values that deviate furthest from the ‘normal’ database median score. These categorizations for ‘extreme’ and ‘normal’ scores were used to describe the sample. Comparisons between the actigraph data of the sleepless and non-sleepless ASD groups were examined by Mann–Whitney U tests (exploration of the data revealed it to be non-normally distributed, even after transformation). A probability of 0.05 or less was considered to have reached a level of statistical significance. Results given are two-tailed owing to the exploratory nature of this work. Student’s t-test was used to examine age differences, and the χ2 test was used to investigate sex differences and school placement between the sleepless and non-sleepless groups. Results THE FAMILIES

Sixty-four of the families had two parents living in the home (two had stepfathers) and the remaining three families had only the mother living in the family home. In ninety per cent of the families there were additional children without an ASD. The research interview was conducted mainly with mothers alone (78%), although mothers and fathers provided information in 17% of interviews, and parents and children gave information in 5% of interviews.

THE CHILDREN

Twenty children attended mainstream school, 32 were placed at a Special Educational Needs Unit, and 17 were at a special school for children with learning disabilities.* At the time of the assessment 18 children were ill or had been ill during the past month, although none was considered by parents to have had ‘significant’ or ‘prolonged’ illness. The illnesses were as follows: cold (n=6), hayfever (n=4), diarrhoea/constipation (n=3), vomiting (n=2), asthma attack (n=1), ear infection (n=1), and migraine (n=1). Eight children had current, uncontrolled epilepsy (five of these with infrequent seizures, less than once a month). None was reported to have nocturnal seizures. Three children had experienced seizures in the past but were seizure-free and had been for more than 3 years, and two children were currently undergoing investigations for possible epilepsy. Thirty-two children were currently taking medication or had done so in the past month. The medications being taken (with the number of children taking each medication in brackets) were as follows: homeopathic medications (n=7), carbamazepine (n=4), antibiotics (type unspecified) (n=2), chlorpheniramine maleate (n=2), essential fatty acid supplements (n=2), haloperidol (n=2), methylphenidate (n=2), paracetamol (n=2), trimeprazine tartrate (n=2), chloral hydrate (n=1), lactulose (n=1), loratadine (n=1), melatonin (n=1), niaprazine (n=1), paroxetine (n=1), pizotifen (n=1), ranitidine (n=1), salbutamol (n=1), sodium valproate (n=1), terfenadine (n=1) and vitamin supplements (n=1). Children were not excluded from analysis on the basis of their health status or medications because this was intended to be a descriptive account of a representative sample. However, it is worth noting that melatonin and chloral hydrate were not being taken during the assessment period itself. AUTISM

Mean age at which parents began to feel concerns about their child’s development was 2 years 2 months (SD 1 year 5 months) and the mean age at diagnosis was 4 years 4 months (SD 2 years 7 months). Forty children had been diagnosed as autistic, 18 as being on the autistic spectrum, and 11 as having Asperger syndrome. Diagnoses had been made by psychiatrists, paediatricians and clinical psychologists according to ICD-10 criteria (World Health Organization 1992). There was a known family history of autistic behaviour in eight families. Of the 18 children diagnosed as being on the autistic spectrum, 14 scored in the range of ‘high probability’ (i.e. more than 68) for a diagnosis of autism according to the Autism Behavior Checklist (Krug et al. 1993) and 4 scored below this cut-off (i.e. 43 to 52), reflecting the ‘spectrum’ nature of this group. SLEEP PROBLEMS

In answer to the question ‘Does your child have a sleep problem or have they had a sleep problem in the past?’, 57 (83%) of the children were reported as having a sleep problem in the past and 46 (67%) were reported as having a current problem. The number of children and the types of sleep problem are shown in Table I. As can be seen, many children had multiple problems. Of the 57 children with a past sleep problem, the problem had persisted until the present time in 36 children. The sleep problems described by parents were those that

have been suggested as being particularly common in children with ASDs. Because spontaneous parental reports are prone to bias, systematic enquiry, using the Simonds and Parraga Sleep Questionnaire (Simonds and Parraga 1982), was made about the frequency of occurrence of the range of current sleep behaviours or features. Table II shows how many children were reported to show each behaviour infrequently (‘Never’ to ‘Two to four times a month’), sometimes (‘Once or twice a week’), or often (‘Three to six times a week’ or ‘Daily’). Some parents were not sure of the frequency; this is indicated by ‘Unsure’. The children showed the same prevalent sleep problems described in previous research (difficulty getting to sleep, night waking, short duration sleep, early morning waking, and daytime sleepiness). As planned, further examination was made of these as yet unexplained sleeplessness problems by dividing the children into two groups: sleepless and non-sleepless, as described in the assessments section under the subheading ‘Sleep history’. On the basis of these criteria, 44 children were defined as having a sleeplessness problem. Other frequent sleep behaviours or features described by the parents (which were few in number) were not considered further in this study because, unlike ‘sleeplessness’ they were either not generally sources of diagnostic confusion (e.g. headbanging) in the way that ‘sleeplessness’ can be, or unlikely to affect the parents or child in any adverse manner (e.g. sleeptalking) and would, therefore, be likely to be more appropriately treated or not require treatment respectively. The sleepless group (n=44) and non-sleepless group (n=25) did not differ significantly in terms of age (t=1.6, df=67, p=1.5) nor sex (χ2=1.66, df=1, p=0.20). Similarly, current health status and medications did not seem to differ, in gross terms, between the sleepless and non-sleepless groups: 25 and 28% respectively, had current illness and 57 and 48% respectively, were currently not taking medication. Current epilepsy did perhaps seem to be more common in the sleepless group (14%) than the non-sleepless group (8%), although the number with current uncontrolled epilepsy was the same in both groups (n=4 in each). The small number of participants with each individual condition or taking each particular type of medication makes any meaningful examination of these factors impossible. Further details of the particular illnesses suffered and medications used in each group of participants are available from the authors on request.

Table I: Spontaneous reports from parents of current and past sleep problems (n=69) Problem

Number of children with sleep problem Past problem Current problem

Difficulty falling asleep Difficulty staying asleep Early waking Headbanging Sleeping in parents’ bed Excessive daytime sleepiness Night terrors Total number with a problem Number with multiple problems

35 43 8 2 16 2 – 57 39

38 18 9 – 5 1 2 46 22

*US usage: mental retardation.

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The distribution of intellectual level did not differ significantly between the groups (χ2=2.87, df=2, p=0.23). The proportions of the sleepless and non-sleepless group attending mainstream school were 23% and 40% respectively; those attending a Special Educational Needs Unit were 48% and 44%; and the proportions placed in a special school were 29% and 16%.

disorder’, i.e. a complaint of sleeplessness; sleeplessness associated with the absence of certain conditions (such as parental presence or watching television); normal sleep quality and quantity when the associations are present; and increased sleeplessness when the associations are absent.

For the 44 children with sleeplessness an attempt was made to identify the sleep disorders underlying their sleep problem according to the diagnostic criteria in the International Classification of Sleep Disorders – Revised (American Sleep Disorders Association 1997). Underlying sleep disorders could be divided into four main groups: behavioural sleep problems; circadian sleep–wake problems; anxiety-associated sleep problems; other/unclassified sleeplessness.

Circadian sleep–wake problems Again, two disorders were identified. The first was ‘delayed sleep-phase syndrome’, i.e. an inability to fall asleep at the desired time; an inability to wake spontaneously or excessive sleepiness; a phase delay of sleep period in relation to desired sleep period; during holidays/weekends a delayed sleep period of normal quantity and quality is maintained and waking is spontaneous. The second was ‘irregular sleep–wake pattern’, i.e. sleeplessness or excessive sleepiness; an irregular pattern of at least two sleep episodes per 24 hours; total sleep time per 24 hours is within normal limits.

Behavioural sleep problems Two disorders were seen The first was ‘limit-setting sleep disorder’, i.e. difficulty in initiating sleep; stalling or refusing to go to bed at an appropriate time; normal sleep quality and quantity once asleep. The second was ‘sleep-onset association

Anxiety-associated sleep problems Although childhood fears are a recognized cause of sleep disturbance of childhood, and methods of treating them appear in paediatric sleep medicine textbooks and parent selfhelp manuals, they are not easily classified according to the

SLEEP DISORDERS

Table II: Current sleep behaviours and features grouped according to frequency of occurrence (n=69) Description Reluctant to go to bed Problems settling to sleep Insists on sleeping with somebody else at sleep onset/in night Waking in night Early waking (before 05:00) Afraid of the dark Fear of death during sleep Fear of going to bed Needs security object Bedtime rituals Sweats a lot while falling asleep Sweats a lot during sleep Startles or jerks parts of the body while falling asleep Startles or jerks parts of the body during sleep Head/body rolling Head banging Sleep paralysis Hypnagogic hallucinations (perceptual distortions when falling asleep) Tooth grinding Bedwetting Restlessness Sleep talking Sleep walking Nightmares Sleep terrors Episodes of confused behaviour Bites tongue during sleep Mouth breathing Snoring Gags, chokes or snorts loudly during sleep Apnoeic episodes Sleeps with neck extended Daytime overactivity Daytime uncontrollable sleepiness Daytime drowsiness

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Unsure

Infrequent

1–2 per week

3+ per week

– – – 1 2 2 14 – 1 – 1 2 1 – 1 – 39 43 – – 2 4 – 3 1 2 1 13 1 – 3 2 4 – –

45 38 49 45 57 39 54 66 35 35 55 38 65 67 64 65 30 26 60 44 36 62 69 64 66 67 68 38 53 64 61 56 33 65 48

9 5 3 6 7 2 – 1 1 1 2 1 – 1 1 1 – – 1 3 5 3 – 1 2 – – 2 2 4 2 3 1 1 8

15 26 17 17 3 30 1 2 32 33 11 28 3 1 3 3 – – 8 22 26 – – 1 – – – 16 13 1 3 8 31 3 13

International Classification of Sleep Disorders – Revised criteria (which are more appropriate for adult patients). Modified, and conservative, criteria were, therefore, used as follows: ‘anxiety-associated sleep disorder’, i.e. sleeplessness associated with (1) specific verbalized concerns and fears or (2) overt physiological signs of anxiety (distress, autonomic nervous system activity, muscular tension) and not alleviated merely by parental presence. Other There was a sizeable minority of participants whose sleep problem could not obviously be classified according to conventional diagnostic criteria. However, as a group they shared common clinical features of their sleep disturbance. These unclassified sleep problems are termed ‘unclassified sleeplessness’: sleeplessness when going off to sleep, in the night and/or in the early morning; during wakeful periods remains in bed and does not call for parents nor indulge in any obviously rewarding activities (e.g. no reading or playing); makes contented noises during wakeful periods (quiet talking to self or giggling); does not fulfil criteria for circadian sleep–wake problems, behavioural sleep problems, or anxiety-associated sleep problems. Parents generally felt that the sleeplessness was a problem for their children because they thought it reduced the child’s total amount of sleep. The number of children showing each type of sleep disorder can be seen in Table III. The behavioural sleep problems were most common, although unclassified sleeplessness featured prominently. The figures in Table IV give the number of children who had single and multiple disorders and the combinations of disorders which were seen. As can be seen, most children had a classifiable, single sleep disorder (with or without unclassified sleeplessness) but there were nine children who seemed to have only unclassified sleeplessness. Children were divided into those aged less than 8 years (n=27) and more than 8 years (n=40; a cut-off age for groups chosen to be comparable with the groups reported in Richdale and Prior [1995]). No association was found between age and the presence of circadian rhythm sleep disorders (χ2=0.0001, df=1, p>0.05), anxiety-associated sleep disorders (χ2=2.01, df=1, p>0.05), or unclassified sleeplessness (χ2=0.001, df=1, p>0.05). However, behavioural sleep problems were more common in the younger age group than in the older children (χ2=6.48, df=1, p=0.01). No significant association between sex and any type of sleep disorder was seen. Four of the eight children with current epilepsy had a problem with sleeplessness: three had behavioural sleep disorders (one with limit-setting sleep disorder, one with sleep-onset association disorder, and one with both of these) and one child had a circadian rhythm disorder (delayed sleepphase syndrome). OBJECTIVE SLEEP DATA

Actigraphs were well tolerated by the children, and data were available for 62 of the 69 children. The seven children for whom no data are available either refused to wear the actigraphs at all or removed them during the night. Table V demonstrates that the objective sleep patterns of children with sleeplessness did not differ significantly in any way from

those children without sleeplessness. It was possible to compare the objective sleep data with normal values (by using Action-W software) for the 46 children aged between 6 and 12 years (ages for which norms were available). Table VI shows the percentage of children falling into the various categories of centile scores. Notable features about the sleep of the children with ASDs were as follows. (1) Time at falling asleep and final waking time were commonly abnormally early or late. (2) Time taken to fall asleep and the length of time awake in the night as well as the number of wakes were abnormally high. (3) The total amount of time spent asleep, as a proportion of time in bed (sleep efficiency), was abnormally low. (4) The overall pattern of activity (Acceleration Index) was commonly abnormal in that the normal values showed a slight increase in level of activity over the night, whereas the children with ASDs either showed a uniform pattern of activity over the night or a much larger increase in activity over time. The meaning of this is unclear but might indicate either an increased tendency to wake up (and thus move more) over time or underlying abnormalities in the pattern of different types of sleep throughout the night.

Table III: Frequency of various sleep disorders underlying reported sleeplessness (n=44) Sleep disorder

Children, n

Subtotal, n

Behavioural sleep problems Limit-setting sleep disorder Sleep-onset association disorder

22 14

36 – –

Circadian sleep–wake problems Delayed sleep-phase syndrome Irregular sleep–wake pattern

6 2

8 – –

Anxiety-associated sleep disorder

8

8

Other/unclassified sleeplessness

19

19

Table IV: Numbers of children with single and multiple sleep disorders (n=44) Disorder

Children, n

Limit-setting sleep disorder (LSSD) Sleep-onset association disorder (SOA) Delayed sleep-phase syndrome (DSPS) Irregular sleep–wake pattern (ISWP) Anxiety-associated sleep disorder (AnSD) LSSD and SOA LSSD and DSPS LSSD and ISWP SOA and DSPS SOA and AnSD LSSD, SOA, and AnSD LSSD, DSPS, and AnSD Unclassified sleeplessness alonea

12 5 1 1 2 3 3 1 1 3 2 1 9

aOf those children with classifiable sleep disorders, 10 also had co-existing unclassified sleeplessness.

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Discussion Results of the current study support the existing literature suggesting that sleep disturbance is a common problem for children with ASDs. In particular, problems going to bed and/or to sleep, staying asleep, and anxiety-related nocturnal behaviour featured prominently in parents’ reports. Although difficult to compare directly, these results have parallels with the results of other studies (e.g. Patzold et al. 1998, Schreck and Mulick 2000) that have found sleeplessness to be prominent. Reported rates of parasomnias in the current study were very low, although without a control group it is not possible to comment about relative rates. As in the general population, the most common sleep disorders underlying the symptoms of sleeplessness were behavioural in origin; that is, the children had not learnt appropriate ways, or had learnt inappropriate ways, of getting to sleep or staying asleep. These disorders were more prominent in the younger children (those less than 8 years old). Such results suggest that it would be appropriate for future intervention studies to evaluate the efficacy of behavioural interventions in this group of children, namely interventions that aim to assist parents with teaching their children appropriate sleep habits and behaviours. Encouragingly, behavioural interventions are used successfully for treating many aspects of behaviour in children with autism (Hall 1997) and several case reports indicate that behavioural interventions can be

effective for treating the sleeplessness-related sleep disorders of children with ASDs (reviewed in Richdale 2001, Schreck 2001) as well as other types of sleep disorders (such as sleep terrors; Durand 2002). However, it cannot be assumed that behavioural interventions will be as effective for sleep problems of children with ASDs as with children from the general population. This is due to their high levels of anxiety, challenging daytime behaviour, use of inappropriate or fixed routines and rituals, and impaired communication and social skills, all of which could potentially make aspects of the implementation of behavioural intervention for sleeplessness more difficult than for children without such problems. Systematic, controlled studies are needed to evaluate the efficacy of behavioural treatments. To investigate this, a randomized, controlled trial is being conducted by the authors based on the results of the current study. Future studies should also be directed towards other types of sleep disorder and their management to ensure that treatment opportunities are not being missed; circadian rhythm disturbance and anxiety-related problems were also well represented in the current series and have been suggested previously as being prominent in children with ASDs (Patzold et al. 1998). The type of unclassifiable sleeplessness noted in this study, involving apparent contentment and positive affect, has also been observed previously in children with ASDs (AL Richdale and K Schreck, personal communication) and in

Table V: Actigraph mean (SD) data of two groups of children with ASD (n=62) and Mann–Whitney U test results Actigraph variable Time at sleep onset Sleep latency, minutes Time at final waking Total sleep duration, hours/minutes Activity (% night with movement) Minutes of wake Number of wakes Duration of longest wake, minutes Sleep efficiency, % Acceleration Index

Sleeplessness (n=38)

No sleep problem (n=24)

Mann–Whitney U

p

22:27 (1:14) 72 (42) 07:14 (00:51) 8/55 (0/46) 40 (12) 39 (38) 11 (6) 14 (14) 79 (10) 0.2071 (0.1490)

21:46 (1:02) 51 (25) 07:03 (00:40) 9/18 (0/60) 38 (12) 38 (32) 11 (6) 15 (12) 83 (7) 0.1742 (0.1762)

178.5 171.0 386.0 358.5 438.0 433.0 440.0 434.0 172.0 406.0

ns ns ns ns ns ns ns ns ns ns

ns, not significant at p