The authors have declared that no competing interests exist.
Children with autism spectrum disorders (ASD) often have difficulties settling to sleep and maintaining asleep through the night. Sleep difficulties are linked to challenging behaviour so understanding the causes of these difficulties is vital. Possible explanations are: (1) that irregular innate cycles lead to difficulties maintaining/initiating sleep at the appropriate times; (2) that children with ASD fail to learn from the contingencies that teach neurotypical children to initiate and maintain sleep. If the cycles are innate then small externally imposed changes in routine will not affect the sleep cycle.
The sleep records of 46 children with autism and moderate to profound intellectual impairments attending a residential school were examined to identify the effects of spring time change and weekend leave on 1) the times children went to sleep, 2) the length of their sleep and 3) the number of sleep disruptions. Manual staff recordings of the children’s sleep were conducted and data for these variables were analysed using repeated measures analysis of variance.
A later sleep time was found in children regarding their sleep onset on Sunday after the time change (average onset was 9:57 p.m. ((s.e. = 8.49 minutes) versus 10:17 p.m. (s.e. = 8.19 minutes), with analysis of variance of sleep onset time showing a significant effect (F (3,41) = 5.02,
In this small pilot study, small changes of day/night cycles appear to have few effects on the sleep patterns of children with ASD attending a residential school. While no significant sleep pattern change was found in this population due to change of clock times or weekend visits, larger epidemiological studies addressing other unexamined variables to better delineate changes in ASD are needed.
Systematic reviews
In general, human sleep is controlled by both external cues (i.e., the time shown on the clock, ambient light, exercise etc) and internal cues (i.e., circadian rhythm, melatonin levels etc)
Small perturbations in sleep cycle are often considered to have minimal consequences
In summary, we have argued that changes in environmental cues would have little effect on the sleep patterns of children with ASD since their internal clocks (represented by melatonin production cycles) are disrupted. The occurrence of variation in environmental cues for sleep such as weekend changes in routine and clock time changes in spring and fall (autumn) offers the opportunity to study how environment may be important. In particular, we hypothesize that:
The change in clock time and hence shift in bedtime produces a shifted sleep pattern with loss of sleep in the springtime change.
Weekends should affect sleep latency, sleep duration or night awakenings.
This study was conducted in a residential school enrolling children with ASD, with a maximum capacity of 46 individuals. The staff at this residential school keep records of sleep at night. Every half hour from nine o’clock in the evening to half past six in the morning, each child is checked to see whether they are asleep. The information gleaned from the records were summarized as: (1) time at which the child fell asleep; (2) number of times the child woke in the night; and (3) the number of hours during which the child was recorded as asleep.
The study was conducted during the period from 18th March 2003 to 15th April 2003. Many of the children returned to their guardians on the weekends (Friday and Saturday night) so the number of children resident varies from night to night. In addition, the routines followed by the staff change are different on Saturday morning and Sunday morning because they do not wake the children at 7am. In order to simplify the analyses and avoid using imputation for missing data we have excluded Friday and Saturday nights from analysis, but we can assume that all children have a different routine on those nights. All the children had received diagnoses of autism according to Diagnostic and Statistical Manual for Mental Illness-Fourth Edition (DSM-IV) criteria, checked by a clinical psychologist with more than twenty years’ experience of diagnosis of autism (not including children with a diagnosis of Asperger’s Syndrome). All the children also had moderate to profound intellectual impairments (IQ estimates in their records indicated a range up to IQ=50).
For the summer time, sleep records were available for these children when the change from Greenwich Mean Time to British Summer Time (i.e., 1 a.m. became 2 a.m.) on the morning of Sunday 30th March 2003 . The dates of interest are the 1st April onwards.
The first time that the child is recorded as asleep is considered to be the time at which the child fell asleep;
The number of discreet occasions on which the child was recorded as being awake after this is recorded as a night time awakening. If consecutive half hour checks reveal the child to be awake, we considered that the child was awake throughout the period;
The number of half hour checks on which the child was recorded as being asleep were noted and recorded as the child’s sleep duration.
Means and standard error (s.e.) values of sleep parameters (sleep onset, sleep disruptions and sleep duration) were reported. The data was analysed by repeated measures analysis of variance, which compares the means, taking account of the variability due to individuals and random factors. The α value was set a priori at 0.05 (i.e. in order for a difference to reach significance it would have to occur less than one in 20 times in a random sample). The minimal clinical significance of a change was set at a change greater than 0.5 of one standard deviation (s.d.).
In order to simplify the analysis, all nights with missing data (March 21, 22, 28, 29, April 4, 5, 11, 12) children were with their parents (Fridays and Saturdays and holidays) were eliminated from the analysis. Thus, a complete set of data for the 46 children was available for 21 nights out of the possible 29 nights between 18th March and 15th April 2003 inclusive. The remaining eight nights for which most data was missing were nights when the children were at home. of these four, were Sunday nights (23rd and 30th of March; 6th and 13th of April) of which one (30th March) was the night after the change to daylight savings time.
The children (39 boys, 6 girls) were aged between 5 years 5 months and 16 years 11 months, with a mean age of 11 years 8 months (s.e. = 2 years 8 months). Eight participants had diagnoses of epilepsy and were being successfully treated at the time with medication. One boy had Fragile X and one girl had Hypomelanosis of Ito.
I – The effect of time changes on sleep parameters
On Sunday nights, the children went to sleep on average at 9:57 p.m. (s.e. = 8.49 minutes). On the night after the change to daylight saving time (i.e., on 30th March) the children went to sleep at 10.17 (s.e. = 8.19 minutes). A repeated measures analysis of variance of sleep onset time on Sundays (March 23rd, 30th, April 6th, 13th) showed a statistically significant effect (F (3,41) = 5.02,
The average number of sleep disruptions per night was 0.07 or about one awakening every fourteen nights. On the night following the time change, 4 night awakenings were recorded for the 46 children. This was due to only three of the children waking during the night, one of whom woke up twice. This does not differ from the number of night awakenings observed on other Sunday nights in the period (Friedman’s analysis of variance by ranks
On average, the 46 children slept for 8 hours 16 minutes. A repeated measures analysis of variance shows significant heterogeneity of variance (Mauchly’s W = 0.002; chi square = 212.5;
The effect of Weekend family visits on sleep parameters during the week
Comparison of Sunday nights to other days of the week in regards to sleep parameters
To examine the effect of weekend changes in awakenings and bedtime onset (the night following the return to school), we compared sleep onset time, sleep disruptions and sleep durations for Sunday nights with the following Monday and Tuesday nights for each of the four weeks. Analysis of the average time to sleep onset, sleep duration, sleep awakenings were conducted.
Using data from all four weeks, statistical analysis shows that the children went to sleep later on Sunday nights than on Monday and Tuesday nights (mean sleep onset time on Sundays = 22:01 s.e. = 7.2 min, Mondays = 21:59, s.e. = 6.6 min), Tuesdays = 21:50 s. e = 7.4 min). The weeks also demonstrated some variability (mean sleep onset time Week 1 = 9:50 s. e = 7.3 min, week 2 = 10:05 s. e = 6.7 min, week 3 = 9:52 s. e 8.2 min, week 4 = 9:58 s. e = 7.3 min. Mauchly’s test for sphericity was significant for the interaction term (W (20) = 0.31,
The number of sleep disruptions was small as noted previously, therefore a Friedman’s test was undertaken, which showed no difference between nights (χ2= 17.04,
Using the data only from Sunday, Monday and Tuesday nights the statistical analysis shows that the children slept for a mean of 8 hours 19 minutes over the three nights on all four weeks examined. There was no significant variability between nights: on Sundays, mean sleep duration was = 8:19 (s.e. 7.6 mins), Mondays = 8:18 (s.e. 5.9 mins), and Tuesdays = 8:17 (s.e. 7.9 mins). Similarly, there was no significant different between weeks: week 1, the mean sleep duration week 1 = 8:12 (s.e. 7.4 mins), week 2 = 8:12 (s.e. 7.4 mins), week 3 = 8:27 (s.e. 7.4 mins), week 4 = 8:22 (s.e. 7.4 mins)). The repeated measures analysis of variance (4 weeks, 3 days –Sunday, Monday, Tuesday) showed that sphericity could not be assumed (Mauchly’s W for the interaction = 0.847,
The children with autism in a residential school showed relatively few sleep disruptions, did not seem to have unusual difficulties falling asleep and slept for about eight hours per night on average. The children went to sleep 20 minutes later in response to a one hour time change. Although such a change is statistically significant it does not reach the minimum test of 0.5 standard deviation change. There was no effect of the time change on the duration of sleep or on sleep disruptions. Analysis of sleep parameters comparing Sundays versus Mondays and Tuesdays showed there were statistically significant variations between weeks and nights on sleep onset, but post hoc tests did not clarify which days or weeks were significantly different. Neither weeks nor days had a statistically significant relationship with sleep disruptions or sleep duration. The effect of weekends on sleep patterns were minor (less than ten minutes) and not clinically relevant. One might therefore conclude that the children with autism studied here were more resilient to changes in sleep cues than other populations.
The study of minor sleep perturbations can reveal useful information about the control mechanisms in sleep. Given that the sleep of children with autism is problematic, this study provides new information about the sleep of that group of children attending a residential school who are subject to time changes and weekly schedule changes. The use of sleep diaries to record sleep is often criticised as not being representative of actigraphic sleep recording. However, in this study the sleep diaries are completed by walking night staff who repeatedly check on the children and respond to unusual noises with additional checks. Actigraphy would undoubtedly have produced a more objective result, however like sleep diaries actigraphy is not a direct measure of sleep.
The use of a naturalistic observational design does not allow one to control for staff expectancies around the time change. It is possible that the night staff may have been expecting difficulties so that they provided stronger cues for the children to fall asleep at the correct time. However, this would suggest that the evidence for social environmental cuing of sleep is stronger than we propose.
Finally, the day on which times change might have an effect which mitigates the disruption caused by the change of hour is not examined in this study. Because the clocks are always changed on a Saturday to Sunday night, the children are usually at home. It is therefore impossible to measure the additional sleep that may be allowed at home to counteract the effects of the time change. However, previous studies of the time change and sleep have shown that the effects last several days
Research on the effects of daylight savings time
The children in this study were going to sleep at about the same time as the children with autism spectrum disorders reported in Wiggs & Stores (14). (W&S sleepless group. 22:27, ok group 21:46, this study 22:00). The number of sleep disruptions reported was small (this study 0.07 per night, compared to cf. Wiggs & Stores
Minor perturbations of routine do not seem to affect the sleep patterns of children with autism who are in a residential environment as much as they affect the sleep of neurotypical populations (cf. Lahti et al.
A study using actigraphy like Wiggs and Stores
Actigraphy – the measurement of activity using electronic methods often considered to provide a more objective measure of sleep than diary records.
ASD – Autism spectrum disorder is a group of neurodevelopmental disorders used in DSM-5 and includes autism, Asperger syndrome, pervasive developmental disorder not otherwise specified (PDD-NOS) and childhood disintegrative disorder. However, in this study we used DSM-4 which only includes autism (without the inclusion of other subtypes such as Asperger or PPD-NOS.
Daylight Saving Time - refers to the practice of advancing the clocks by one hour during the summer months so that the evenings are longer.
Neurotypical- used to describe people with no known neurological abnormalities which might affect thinking, learning or behaviour. It is usually contrasted with one or more populations known to have abnormalities affecting one or more of thinking, learning or behaviour.
Zeitgeber – (from German) a notional biological clock which determines sleep wake cycles or shorter duration rhythms. Often considered to be relatively independent of the environment.