OBJECTIVE: To assess the effectiveness of a weighted-blanket intervention in treating severe sleep problems in children with autism spectrum disorder (ASD).
METHODS: This phase III trial was a randomized, placebo-controlled crossover design. Participants were aged between 5 years and 16 years 10 months, with a confirmed ASD diagnosis and severe sleep problems, refractory to community-based interventions. The interventions were either a commercially available weighted blanket or otherwise identical usual weight blanket (control), introduced at bedtime; each was used for a 2-week period before crossover to the other blanket. Primary outcome was total sleep time (TST) recorded by actigraphy over each 2-week period. Secondary outcomes included actigraphically recorded sleep-onset latency, sleep efficiency, assessments of child behavior, family functioning, and adverse events. Sleep was also measured by using parent-report diaries.
RESULTS: Seventy-three children were randomized and analysis conducted on 67 children who completed the study. Using objective measures, the weighted blanket, compared with the control blanket, did not increase TST as measured by actigraphy and adjusted for baseline TST. There were no group differences in any other objective or subjective measure of sleep, including behavioral outcomes. On subjective preference measures, parents and children favored the weighted blanket.
CONCLUSIONS: The use of a weighted blanket did not help children with ASD sleep for a longer period of time, fall asleep significantly faster, or wake less often. However, the weighted blanket was favored by children and parents, and blankets were well tolerated over this period.
- ABC —
- Aberrant Behavior Checklist
- ASD —
- autism spectrum disorder
- CONSORT —
- Consolidated Standards of Reporting Trials
- CROS —
- crossover analysis
- CSDI —
- Composite Sleep Disturbance Index
- SCQ —
- Social Communication Questionnaire
- SOL —
- sleep onset latency
- SSPCQ —
- Short Sensory Profile Caregiver Questionnaire
- TST —
- total sleep time
What’s Known on This Subject:
Children with autism sleep poorly compared with their peers. Sensory integration, including use of weighted blankets, is proposed as a means to reduce arousal and stress. There is, however, no evidence that weighted blankets can improve sleep for these children.
What This Study Adds:
This is the first robust study to evaluate the impact of weighted blankets and show that they do not improve sleep parameters in children with autism spectrum disorder.
Children with autism spectrum disorder (ASD) are more likely to have disturbed sleep than typically developing children, with a prevalence of sleep disturbance in children with ASD between 40% and 80%.1 The most commonly reported sleep disturbances are increased sleep latency (time to fall asleep) and frequent night waking, which result in reduced sleep duration.2 The etiology of sleep disorders in ASD is poorly understood.3 Sleeping difficulties are frequently chronic, resulting in additional learning and behavior problems4 and affecting the whole family’s well-being. Behavioral interventions work with some children, but not all.5 Pharmacological interventions, with exogenous melatonin, have shown potential for reducing sleep latency by ∼30 minutes but have a less significant impact on total sleep time (TST).6,7
Weighted blankets are often recommended by professionals who work with young people with ASD to assist with calming and relaxation, as well as to assist with sleeping.8,9 The theory underlying the reasons for using weighted blankets and other weighted items for calming purposes is based on sensory integration.10 It is hypothesized that the deep pressure and more consistent sensory input provided by weighted items reduces the body’s physiologic level of arousal and stress, which might improve sleep. Although weighted blankets potentially offer a relatively cheap, nonpharmacologic intervention, research on their efficacy in children with ASD is lacking. This trial was therefore conceived to establish whether this novel intervention could increase TST and improve other sleep parameters in children with ASD.
Study Design and Oversight
This randomized, multicenter, controlled, crossover phase III trial was undertaken in 3 sites in England. The study was approved through the UK Integrated Research Application System and the review board of each participating center and was conducted in accordance with the International Conference on Harmonization Good Clinical Practice Guidelines and the Declaration of Helsinki. Written informed consent was obtained from the legal guardians of the children. Informed written assent was also obtained from competent study participants between 8 and 16 years of age.
Children were eligible to participate if they were aged between 5 years and 16 years 10 months and had an ASD diagnosis and if their parents reported a sleep problem (as defined later), for at least the previous 5 months. The diagnosis of ASD was reached if clinical records from the local multidisciplinary team agreed to an unequivocal ASD diagnosis including autism, Asperger syndrome, or pervasive developmental disorder not otherwise specified. In addition to consideration of school reports and direct observations, these teams used a range of standardized diagnostic instruments reflecting usual ASD diagnostic practice in the United Kingdom.11,12 Sleep problems were characterized as failing to fall asleep within 1 hour of “lights off” on 3 of 5 nights and/or achieving <7 hours of continuous sleep on 3 of 5 nights. Children were not included if they were known to suffer from obstructive sleep apnea, night terrors, or other disorders likely to have an impact on sleep. Two amendments were made to the eligibility criteria after trial commencement: the age for inclusion was raised by 1 year to 16 years 10 months, and patients on a stable dose of permitted medication for >6 months were included (see protocol). These changes were to maximize recruitment without affecting trial fidelity.
A number of commercially available weighted blankets in common use that adhered to the original guidance on sensory interventions as proposed by Ayres10 (providing constant proprioceptive stimulation distributed across the body) were considered by the senior occupational therapist of this study (DG). A specific weighted blanket used in the United States and United Kingdom was chosen. The weighted blanket weighed 2.25 kg (small) or 4.5 kg (large) and was heavy without being thick (and therefore too warm) through the use of 3-mm steel shot pellets embedded evenly throughout the blanket. Although we were aware that blinding child and parent to the different weights of study and control blanket was impossible, we matched the control blankets by size, color, and texture of the material. Some children with ASD during pilot stages were aware of the subtle texture of the weighted blankets’ steel shot, and so we commissioned the suppliers to incorporate lightweight plastic beads identical in size to the steel shot into the bespoke control blankets.
Two sizes of blankets (small: 147 × 76 cm; large: 152 × 152 cm) according to the size of child were used, consistent with recommendations by manufactures and therapists.
After screening and consent, eligible participants began a baseline adaptation and monitoring period of 7 to 21 days.
During treatment phases, each blanket was used for 12 to 16 days, with actigraphy and sleep diary monitoring. After the first treatment phase, the researchers removed the initial blanket, diaries, and actigraph and provided the next blanket, actigraph, and new sleep diaries. Care was taken to ensure that the baseline and intervention phases were conducted during school-term time and that no breaks occurred between interventions (avoiding school holiday periods, for example). All interviews and data collection were carried out by the researchers and visits took place in clinic, within designated schools, or whenever possible, the patients’ homes.
Remote randomization was carried out by Kings Clinical Trial Unit by using block randomization with random variable block lengths of 2 and 4, and stratified by center. Randomization requests were generated by the researchers, who then dispensed the allocated treatments. Because of the nature of the treatment, researchers were unblinded; however, all trial investigators (PG, DG, LW, BW) and the statistician (VA) were blind to treatment allocation throughout the trial and analysis.
The trial design included both objective (actigraphy) and subjective (parent-completed diary) measures of sleep as recommended by Sadeh.13 There are benefits with each approach and also reasons the results may not be concordant14,15; for example, sleep diaries would not detect periods when the child was awake but not disturb the household (a particular concern for determining sleep onset latency [SOL]), and actigraphy may interpret restless sleep as being awake.
The actigraph (Micro Mini Motionlogger, Ambulatory Monitoring, Ardsley, NY), an accelerometer, was worn on the nondominant wrist, and movement was monitored continuously and stored within the unit. Subsequent analysis of frequency and pattern of movement by means of validated algorithms permits detection of basic sleep–wake patterns.13 Movements were scored in 1-minute epochs; all epochs that are scored above a preset threshold using an algorithm by Sadeh13 are scored as “awake” and those that are below this threshold are scored as “sleep.”
Various assessments of sleep parameters, sensory profiles, daytime behaviors, and perceptions of blanket use were conducted at different time points (Table 1).
The primary outcome was TST, measured by actigraphy. A minimum of 5 of 7 nights’ actigraphy data (or ≥71% if >7 nights were captured) was required at baseline and during each blanket phase, and averages were calculated at each time point. Children not meeting this requirement were excluded from the data analyses of the main research questions.
Secondary sleep outcomes included TST measured by parental diary; SOL measured by diaries and actigraphy; and sleep efficiency (the proportion of time spent in bed asleep) measured by actigraphy.
Three questionnaires were completed at baseline and at the end of both intervention periods: the Composite Sleep Disturbance Index (CSDI; frequency and duration of sleep problems),16–18 the Aberrant Behavior Checklist (ABC; to assess behavioral problems),19,20 and the Sensory Behavior Questionnaire (SBQ; sensory stimuli response profile).21 Three questionnaires were only completed at baseline: the Children’s Sleep Habits Questionnaire (a parent-report validated sleep screening instrument), the Social Communication Questionnaire (SCQ; a screening instrument for ASD),22 and the Short Sensory Profile Caregiver Questionnaire (SSPCQ; a questionnaire to establish a profile of children’s sensory responses).23 The trial flowchart can be seen in Fig 1.
Children and parents also completed subjective ratings of sleep quality and acceptability of the blanket. The sleep diary contained a section for parents to estimate the percentage of the night the blanket was in contact with the child’s body.
The frequency and severity of adverse events were monitored carefully through a 24-hour telephone number and weekly parent reviews (face-to-face or telephone).
The “intention to treat” principle was used throughout, with analyses undertaken by using SPSS (version 20; SAS Institute, Cary, NC).24 Missing data for questionnaire responses were prorated if <10% was missing, and data were excluded otherwise.
The TST primary outcome (actigraphy) was analyzed by taking the average TST over baseline and each of the 2-week intervention periods. It was powered at 80% with a 5% significance level to detect a change from baseline of 40 minutes between the study blanket and placebo blanket periods using a common SD of 1.7.24,25 Allowing for 20% missing data based on pilot work, 63 in total were required.
The actigraphy data and sleep diary outcomes were analyzed by taking the average TST (actigraphy and diary) and average SOL (actigraphy and diary) over the baseline and each of the 2-week intervention periods. At baseline a descriptive summary was undertaken between the randomization groups, with mean (SD) or median (interquartile range) for continuous data and n (%) for categorical data. No statistical tests were used to compare baseline data (Consolidated Standards of Reporting Trials [CONSORT]; http://www.consort-statement.org/downloads).
The primary analysis was to compare TST when using weighted blanket versus control blanket (actigraphy). To rule out a period effect, a crossover analysis (CROS) was undertaken. The sum of the TST values was calculated for the time period when using weighted blanket and when using control blanket for each subject. This was compared across the sequence groups by means of an independent t test. Where the test was not significant, this indicated that there was no evidence of a period effect.26 The second stage of CROS is to test the difference between the weighted blanket and the control blanket. The differences in the TST were calculated between the first period and the second period, and this difference was compared across the sequence groups by means of an independent t test. This method of analysis adjusts for the period effect and so reduces the effect of any period difference.
This was then followed by the more conventional analysis of a CROS by using a paired t test to compare TST when using weighted blanket versus TST when using control blanket, which was irrespective of starting group. The existence of crossover effects must be ruled out before this method is valid (see http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3345345).
The same statistical procedures were followed for secondary sleep data. For data from the SPBQ, ABC, and CSDI, a CROS was again undertaken, by using Mann-Whitney tests to examine the crossover effect. A Wilcoxon paired test was then used to compare the study blanket and control blanket scores, irrespective of starting group where the existence of crossover effects was ruled out. Exploratory analysis of sensory influences on TST in response to blankets was undertaken by using repeated-measures analysis of variance.23
All analyses were performed on SPSS (version 20; IBM SPSS Statistics, IBM Corporation). P < .05 was considered to indicate statistical significance.
Seventy-three children were recruited and followed up between August 2011 and October 2012.
Seventy-three patients were randomized, and 6 were subsequently excluded. Four could not tolerate or declined to use the weighted blanket, 1 chose to withdraw to attend an alternative clinic, and 1 had an unrelated illness and could not continue. The baseline characteristics of the 2 groups can be seen in Table 1.
It is interesting to note that despite agreed ASD diagnoses from multidisciplinary teams, 13 (19%) were not above the recommended cutoff of 15 on the SCQ, but of these 11 were above the cutoff of 11 discussed in the review by Norris and Lecavalier27 as the cutoff with maximum sensitivity and specificity.
The baseline average TST was 453.3 (60.0) minutes, average SOL (latency) was 77.1 (44.8) minutes, average sleep efficiency was 72.6% (8.7), average duration of wake after sleep onset was 85.4 (45.1) minutes, and the average number of night wakenings was 21.2 (8.1). There were no differences at baseline between the 2 randomization groups (see Table 2).
TST (Primary Outcome)
There was no evidence of a period effect for TST (t52 = 0.996, P = .324). When testing for differences between the weighted blanket and control blanket by looking at the within subject differences in the outcome by sequence groups, there was no significant difference (t52 = 0.893, P = .376). For sequence group weighted-control, the TST was only slightly longer when using control compared with weighted (mean difference [weighted-control] = –0.7 [31.2]), and for sequence group control-weighted, the TST was slightly longer when using control compared with weighted (mean difference [control-weighted] = 7.7 [37.8]). This was confirmed by a paired t test comparing study blanket and control blanket, irrespective of starting group (t53 = 0.896, P = .374). The mean difference was –4.2 (34.5, 95% confidence interval –13.6 to 5.2). Hence, overall there was no significant difference in TST between the study blanket and control blanket (see Table 3 for details of primary and secondary sleep outcomes).
Sleep Latency, Sleep Efficiency, and Wake After Sleep Onset (Secondary Outcomes)
Similarly there was no evidence of a period effect, within subject differences in the outcome by sequence groups, or overall significant differences between study and control blanket for sleep latency, sleep efficiency, or measures of wake after sleep onset (see Table 3 for details).
The baseline average TST was 531.8 (109.6) min, average SOL (latency) was 70.0 (47.6), the average time of the night wake was 16.7 (12.8), and the average proportion of nights with at least 1 wake was 0.30 (0.34). There were no differences at baseline between the 2 randomization groups (see Table 2).
In keeping with the actigraphy, there was no evidence of a period effect, within-subject differences in the outcome by sequence groups, or overall significant differences between study and control blanket for TST, sleep latency, measures of wake after sleep onset, or parents’ perception of percentage the blanket was worn each night (see Table 3).
Table 4 summarizes the questionnaire outcomes. The CSDI showed a clinically small (0.74) but statistically significant (P = .010) lower score (better sleep) during the control blanket period. There were no significant differences for the total scores or subscales between the weighted blanket and the control blanket for the SPBQ or ABC.
Table 5 summarizes results of the child and parent scales used to assess perceived sleep quality and blanket acceptability. More children chose the “really liked” category for the weighted blanket than control blanket (48% vs 31%). More parents felt that sleep was “very much/much improved” (51% vs 16%) and their child calmer (35% vs 14%) with the weighted blanket than control blanket.
No serious adverse events were reported, and other than a 2-day skin rash on 1 child that may have been related to the blanket, all others were unrelated illness (eg, colds, fever, chicken pox, broken bone in hand). No formal statistical tests were undertaken, and the results for each group appeared similar.
Results of exploratory analyses are provided in Table 6. The treatment effect was not modified by age, weight, baseline degree of sleep problems, SCQ autism severity score, or initial sensory profile on the SSPCQ.
In this randomized controlled CROS, a weighted blanket intervention was found to be no more effective than a control (usual weight) blanket at improving TST or any other commonly measured parameter of sleep quantity or quality. This was regardless of whether parameters were measured objectively by actigraphy or subjectively with parent diaries. There were no adverse events. Interestingly, children were more likely to like the weighted blanket and parents more likely to rate their child’s sleep as better, despite no actigraphy or diary evidence to support this. Parents also rated their child’s behavior as calmer when using the weighted blanket. It is possible these findings are related to a perception of improved sleep brought about by improved bedtime behavior, positive attributions about the intervention that affected perceptions or parent child interactions, or that parents were influenced by a desire to please the study team or reinforce widely held beliefs about weighted blankets. It is also possible that parents were aware of some qualitative change in the child that our measures did not capture.
The strengths of our design include (1) the first randomized study specifically designed and powered to assess the impact of a weighted blanket on TST in children with ASD, (2) the purposive inclusion of a “placebo” control, (3) the use of an objective assessment of sleep, (4) the inclusion of secondary outcomes that included sensory and other daytime behaviors, and (5) findings generalizable to children diagnosed in community settings with ASD and poor sleep.
Limitations include the following: (1) the weighted blankets were obviously heavier than the control blankets, making true masking of weighted versus control impossible. This made a placebo response more likely and was the main reason we decided that subjective outcomes such as sleep diaries would not suffice, choosing instead actigraphy as the most practical objective measure. The run-in period helped maximize the number of children who tolerated actigraphy, and, in contrast to other studies using the same methodology, this technique provided robust objective primary outcome data across >95% of the children recruited. (2) The parental estimation of percentage of blanket contact is likely to be extremely subjective, and we acknowledge this, but we believe it was important to have some estimate of “adherence and concordance” to treatment. If this study were to be repeated, then concurrent infrared video would enable a more precise analysis. (3) Although the study was powered to detect a 40-minute difference in TST with >63 patients, only 54 subjects were available for the weighted blanket–control comparison. The mean differences of ∼4 minutes, however, were not significant, and an additional 9 patients would not have altered the study outcome. (4) This was a pragmatic trial, thus we did not exclude children who were on stable medications and constant doses. It is possible that some of these medications could have altered sleep parameters. However, the randomized crossover design means any effect would be present during both arms. Baseline data show that no child was on medication that was “normalizing” sleep, and all subjects had sufficiently poor TSTs to leave room for improvement.
Weighted blankets are widely available commercially, and anecdotal reports promote their use in children with ASD. The blankets will cost families in excess of £100/115EU/$150 and cannot be returned to manufacturers if they are not effective. Our findings provide valuable evidence that although weighted blankets in children with ASD are safe and well perceived by child and parent alike, there is no measurable evidence they are beneficial for children’s sleep.
The Snuggledown Group acknowledges the support from our funders, Research Autism, the Waterloo Foundation, and the Baily Thomas Charitable Foundation. The group also expresses its gratitude to the children and families who participated in this study and the schools that kindly hosted interviews: Milestone School, Hawkedown Primary School, Alexandra Infant School, and Sonning Primary School. Finally, thank you to Rachael Fallows for concept planning and Dr Sri Gada for his help with recruitment of families.
This study was supported by the United Kingdom Clinical Research Collaboration-registered King’s Clinical Trials Unit at King’s Health Partners, which is in part funded by the NIHR Biomedical Research Centre for Mental Health at South London and Maudsley NHS Foundation Trust and King’s College London and the NIHR Evaluation, Trials and Studies Coordinating Centre.
To access the full trial protocol, please go to: http://researchautism.net/pages/research_autism_projects_studies/research_autism_project_028
- Accepted April 30, 2014.
- Address correspondence to Paul Gringras, MBChB, MRCP, MsC, Evelina Children’s Hospital, St Thomas’ Hospital, Lambeth Palace Rd, London, SE1 7EH, United Kingdom. E-mail:
Professor Gringras was involved in the design of the study, the funding application, development of the protocol, and recruitment of patients as a local principal investigator; was co–chief investigator for the trial and a member of the trial management group; and cowrote the article; Dr Wiggs contributed to the design of the study, the funding application, and development of the protocol; advised on the use of actigraphy and patient-reported outcomes; was principal investigator and co–chief investigator for the trial; was a member of the trial management group; and helped write the article; Ms Rush coordinated the trial, recruited patients, scored actigraphy, helped write the article, and was a member of the trial management group; Ms Sparrowhawk and Ms Pratt recruited patients, helped write the article, and were members of the trial management group; Dr Wright helped recruit patients and coordinate the trial, helped write the article, was co–principal investigator for the trial, and was a member of the trial management group; Ms Hooke and Ms Moore helped recruit patients, respond to family queries, and collect and record data; Dr Allgar helped with the statistical analysis plan, analyzing data, and writing the article; Dr Green contributed to the design of the study, the funding application and ethical submission, advised on the use of sensory questionnaires and patient reported outcomes, helped write the article, and was a member of the trial management group; and Dr Zaiwalla helped with the initial study design and recruitment as lead clinician from the Oxford Group and helped write the article.
FINANCIAL DISCLOSURE: The authors have indicated they have no financial relationships relevant to this article to disclose.
FUNDING: Supported by Research Autism, the Waterloo Foundation, and the Baily Thomas Charitable Foundation.
POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose.
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