sleep patterns and daytime sleepiness in adolescents and young adults with williams syndrome

Brief report

Sleep patterns and daytime sleepiness in adolescentsand young adults with Williams syndrome

S. E. Goldman,1 B.A. Malow,1 K. D. Newman,2 E. Roof2 & E. M. Dykens2

1 Sleep Disorders Program, Department of Neurology,Vanderbilt University Medical Center, Nashville,TN, USA2 Vanderbilt Kennedy Center for Research on Human Development, Nashville,TN, USA

Abstract

Background Sleep disorders are common in indi-viduals with neurodevelopmental disorders and mayadversely affect daytime functioning. Children withWilliams syndrome have been reported to have dis-turbed sleep; however, no studies have been per-formed to determine if these problems continueinto adolescence and adulthood.Methods This study examined overnight sleep pat-terns and daytime sleepiness in 23 adolescents andadults with Williams syndrome age 25.5 (8.0) years[mean (SD)]. Interviewer-administered sleep ques-tionnaires were used to evaluate nighttime sleepbehaviours and daytime sleepiness. Wrist actigraphywas used to evaluate sleep patterns.Results Although individuals in our sample aver-aged 9 h in bed at night, daytime sleepiness andmeasures of sleep disruption were common andcomparable to those of other populations with neu-rodevelopmental disorders. These measuresincluded reduced sleep efficiency [74.4 (7.0)%]with prolonged sleep latency [37.7 (37.3) min],

increased wake time after sleep onset [56.1(17.6) min], and an elevated movement and frag-mentation index [14.3 (4.6)].Conclusion Adolescents and young adults withWilliams syndrome were found to be sleepy despiteaveraging 9 h in bed at night. Implications are dis-cussed for associated causes of sleep disruption andfuture polysomnographic evaluation.

Keywords adolescents and young adults, daytimesleepiness, sleep patterns, Williams syndrome

Introduction

Williams syndrome, a developmental disorderresulting from a microdeletion of several genes onchromosome 7q11.23, results in cardiovascular,endocrine and neurological problems (Pober &Morris 2007). Williams syndrome is associated witha distinctive cognitive-linguistic profile, marked byvisual-spatial deficits and relative strengths inexpressive language. Individuals with Williams syn-drome also have high levels of non-social anxiety,worries and fears, as compared with others withintellectual disabilities (ID) (Einfeld et al. 1997;Davies et al. 1998; Dykens 2003), even though they

Correspondence: Suzanne Goldman, Vanderbilt University MedicalCenter, Department of Neurology, Sleep Disorders Program, 1301

Medical Center Dr, Room B-727, Nashville TN 37232, USA(e-mail: [email protected]).

Journal of Intellectual Disability Research doi: 10.1111/j.1365-2788.2008.01140.x

volume 53 part 2 pp 182–188 february 2009182

© 2008 The Authors. Journal Compilation © 2008 Blackwell Publishing Ltd

mailto:[email protected]

show marked sociability and interests in interactingwith others. In addition, children with Williams syn-drome may exhibit over activity and short attentionspans. Approximately 65% are diagnosed withattention-deficit hyperactivity disorder (ADHD) orother behavioural disorders (Einfeld et al. 1997;Dykens 2003; Leyfer et al. 2006; Pober & Morris2007). Both mental health and medical problemspersist into adulthood, and may reduce adultquality of life (Davies et al. 1998; Howlin & Udwin2006).

Sleep is one aspect of the Williams syndromephenotype that has yet to be adequately character-ized. Sleep disorders are common in individualswith developmental disorders, and persist if nottreated (Lancioni et al. 1999). Prevalence ratesrange from 13% to 86% dependent on age, physicaland mental impairment, and genetic syndrome(Didden & Sigafoos 2001). To date, only one studyhas specifically looked at sleep in Williams syn-drome. Parents of 28 children [mean age (SD = 4.7(2.3) years] participated in a telephone survey toexamine possible sleep problems (Arens et al. 1998).The authors reported, based on parental response,that 16 children (57%) had symptoms consistentwith a possible sleep disorder. In particular, restlesssleep, awakening and sleep initiation were reported.Polysomnography was performed on seven of thesechildren and the authors reported a periodic limbmovement index that was fivefold greater in thesechildren than in control subjects. These childrenalso had a greater amount of sleep time spentawake than control subjects. Based on this study,and extrapolating from the literature on sleep innormal children, it was suggested that children withWilliams syndrome may be at risk for sleep disrup-tion because of limb movements, restless leg syn-drome or sleep disordered breathing (Mason &Arens 2006). These authors further suggest that asleep history should be included in the clinicalevaluation of children with Williams syndrome.Clinically, sleep complaints are believed to persistinto adulthood (Pober & Morris 2007), althoughstudies have yet to examine the nighttime sleep pat-terns and associated daytime sleepiness in adoles-cents or adults with Williams syndrome.

Disturbed sleep in neurodevelopmental disordersis associated with poorer daytime function andbehaviour (Malow & McGrew 2008). Given their

high levels of fears and anticipatory anxiety, wewished to explore whether disturbed nighttime sleepmight be present in our adolescents and adults withWilliams syndrome. If present our work would thenprovide a basis for future interventional studiesaimed at improving sleep in Williams syndrome,with the goal of improving anxiety and otherdaytime behaviours. The primary objective of thisstudy is to describe the sleep patterns of adoles-cents and adults with Williams syndrome usingsleep questionnaires and wrist actigraphy.

Method

Participants

We examined nighttime sleep patterns and daytimesleepiness in 23 adolescents and adults with Will-iams syndrome (12 males, 11 females) using struc-tured interviews and wrist actigraphy. Participantswere recruited during a residential summer musiccamp offered through the Vanderbilt KennedyCenter for Human Development. Participantsranged in age from 17 to 35 years, with a mean ageof 25.5 (8.0) years. As identified by the KaufmanBrief Intelligence Test-2 (K-BIT-2) (Kaufman &Kaufman 2004), participants’ overall mean IQ was66.1 (14.5). Consistent with the cognitive profileoften seen in Williams syndrome, participantsshowed, on average, better developed verbal skills[K-BIT-2 verbal IQ = 79.3 (15.8)] than non-verbalskills [K-BIT-2 non-verbal IQ = 60.6 (17.7)]. Allparticipants but two lived at home with theirparents; two individuals resided with a roommate ina supervised, supported living apartment in closeproximity to their families. Prior to arrival at thesummer music camp, parents of all participantswere asked if they felt their child would be able toindependently participate in this study and all feltthey would be able to. This study was approved bythe Vanderbilt University Medical Center Institu-tional Review Board and all participants providedinformed consent.

Procedure and instruments

Participants completed an interviewer-administeredsleep habits questionnaire which included theEpworth Sleepiness Scale (ESS), a validated ques-

183Journal of Intellectual Disability Research volume 53 part 2 february 2009

S. E. Goldman et al. • Sleep and daytime sleepiness in Williams syndrome


tionnaire to measure excessive daytime sleepiness inadults. The ESS is widely used in sleep medicine toevaluate daytime sleepiness. The ESS consists ofeight questions designed to evaluate an individual’spropensity to fall asleep during routine daytimesituations. The ESS has a test–retest reliability witha Pearson correlation coefficient of 0.822 in circum-stances where daytime sleepiness was expected tobe stable, and a Cronbach’s alpha = 0.88 for inter-nal consistency (Johns 1991; Johns 1992). A scoreof >10, out of a possible 24, on the ESS is indica-tive of increased daytime sleepiness (Johns 1994).Participants were also asked how often they awokeduring the night, and for what reason; if they feltthey had problems sleeping at night (yes/no); if theysnored (yes/no); and if they were tired during theday (yes/no). Finally, participants were also askedabout feelings in their legs. If they acknowledged legsymptoms, they were queried further as to the timeof day and the character of these sensations.

Three to 4 weeks after the camp ended, partici-pants were contacted to see if they would be willingto wear a wrist actigraph and complete a sleep–wake diary to measure nighttime sleep. A total of 17

individuals assented and they were sent wrist acti-graphs (MiniMitter® AW 64 Mini-Mitter, Respiron-ics, Bend, OR, USA). These 17 individuals did notdiffer from the larger group of 23 participants indemographic variables, sleep or behavioural fea-tures. The actiwatch is a small computerizedwristwatch-like device that is used to detect move-ment (Sadeh & Acebo 2002) and is used as a surro-gate measure of sleep and wake. It was worn on thenon-dominant wrist over seven consecutive 24-hperiods. The actiwatch has been validated as ahighly reliable method to differentiate sleep fromwake (Sadeh et al. 1995; Jean-Louis et al. 2001;Sadeh & Acebo 2002; Ancoli-Israel 2005). It iswidely used in sleep research and sleep medicine.The actigraph was set to record in 1-min epochs ata medium sensitivity level for scoring sleep andwake times (40 activity counts/min) (Oakley 1997);Mini-Mitter Co. Inc 2004). Participants were sent asleep–wake diary to complete concurrent withwearing the watch. Each day, participants recordedthe time they went to bed, woke up in the morningand the number of times they awoke during thenight. All participants were instructed in the use ofthe actigraph and how to complete the sleep diary.

Telephone support was available throughout themonitoring period.

Data from the actigraphs were downloaded to apersonal computer where all sleep intervals weremanually placed on the actogram based on the timerecorded in the participants’ diary. Time in bed wasdefined as the time elapsed from lights out (the setsleep start) to lights on (the set sleep end). Thetotal nighttime sleep duration was the sum of allsleep epochs within the interval between the timeset on the actogram for nighttime sleep andmorning wake time. Sleep efficiency was calculatedas the ratio of total nighttime sleep duration to thetotal time in bed. Sleep latency was calculated asthe time required for sleep onset after attempting toget to sleep. Wake after sleep onset (WASO) wasmeasured as the sum of all wake epochs during thesleep period and reflects the number of minutesscored as wake that exceeded the sensitivity thresh-old. The movement and fragmentation index(MFI), often referred to as an index of restlessness,was calculated by the software as the sum of the percent of mobile minutes plus the per cent of immo-bile bouts less than 1-min duration to the numberof immobile bouts, for a given interval. The MFIcaptures all movement regardless of the intensity ofthe movement. All sleep variables were calculatedusing Actiware Version 5 software (Mini-Mitter Co.,Bend, OR, USA).

Statistical analyses

Descriptive statistics were conducted on all majorvariables. Associations were measured with Spear-man correlation. Nonparametric Wilcoxon-RankSum Tests were used to test differences in meansbetween dichotomous variables, and chi-squaredanalyses were used for categorical variables betweenindividuals. Results are presented as mean (SD)and significance is at P � 0.05. Analyses were runusing sas Version 9 software (SAS Institute, Cary,NC, USA).

Results

Demographics

No significant differences were found betweenmales and females on any sleep variable. Similarly,




no significant differences were found by age for anysleep variable.

Subjective sleep perception

Ninety-five per cent of the participants indicatedthat they felt tired during the day, with over 1/3(34.8%) having excessive daytime sleepiness as mea-sured by an ESS score �10.

Ninety-one per cent of participants reportedawakening at least one time per night to use thebathroom, with over 65% of participants reportingawakening two or more times per night. Other symp-toms included snoring in 22.7%, and urge to movetheir legs in 13.6% (see Table 1).The majority of ourparticipants responded that they were tired duringthe day, felt that they had sleep problems and statedthat, if possible, they would like to sleep more.

Actigraphy-measured sleep

Time in bed, documented with wrist actigraphy,averaged 9.0 (1.1) h and the average nighttime sleep

duration was 7.6 (1.2) h. The average sleep latencywas 37.7 (37.3) min. Sleep efficiency was 74.4%(7.0) and the measures of disruptive sleep in thesample overall were high, including 56.1 (17.6) minof WASO and an MFI of 14.3 (4.6).

Discussion

To our knowledge, this study is the first to specifi-cally examine sleep patterns in adolescents andadults with Williams syndrome. Through the use ofactigraphy, an objective measure of sleep patterns,and subjective questionnaires, we were able todescribe the sleep concerns and patterns in thisgroup of individuals. The majority of our partici-pants acknowledged sleep problems and daytimetiredness. We documented that these individualswere sleepy even though they are spending anaverage of 9 h in bed at night, and averaging 7.5 hof sleep.

We postulate that the daytime sleepiness that ourpatients reported is due to sleep disruption. Sleepdisruption in the population may be caused by mul-tiple factors including nocturia, restless legssyndrome/periodic limb movements of sleep,obstructive sleep apnoea or factors intrinsic to Will-iams syndrome. Children with Williams syndromehave been reported to have periodic limb move-ments in sleep with associated arousals and awaken-ings (Arens et al. 1998), and these symptoms havealso been reported in adults (Davies et al. 1998;Mason & Arens 2006). Individuals in our studyreported unpleasant sensations in their legs whenlying down at night symptoms suggestive of possiblerestless legs syndrome. While most individuals withrestless leg syndrome have periodic limb movementsof sleep, periodic limb movements of sleep canoccur independently of restless legs syndrome andare diagnosed by polysomnography. Therefore, wecannot exclude periodic limb movements of sleep asa potential cause of perceived sleepiness in theseindividuals.

Nocturia is another potential cause of sleep dis-ruption in our population. The majority of our par-ticipants reported the need to urinate at least onceduring the evening with a large per cent reportingthis need multiple times. A high prevalence ofurinary frequency, and incontinence, has been

Table 1 Sleep and behaviour characteristics of Williams syndromeadolescents and adults

Totaln = 23

Mean (SD)Age (years) 25.5 (8.0)Epworth Sleepiness Scale 8.7 (4.4)Subjective sleep perception* % yes

Have problems with sleep 36.4Want to change their sleep 76.7Sleepy during the day 77.3Tired during the day 95.2Nocturia 90.5Snores 22.7Restless leg symptoms 13.6

Actigraphy-measured sleep (n = 17)† Mean (SD)Time in bed (h) 9.0 (1.1)Sleep duration (h) 7.6 (1.2)Sleep onset latency (min) 37.7 (37.3)Sleep efficiency (%) 74.4 (7.0)Wake after sleep onset (min) 56.1 (17.6)Movement and fragmentation index 14.3 (4.6)

* Responses to sleep interview questions asked were based on ayes/no scale.† Variables calculated by Actiware V5 software (Mini-Mitter Co.,Bend, OR, USA).




reported in children and adults with Williams syn-drome (Schulman et al. 1996; Cherniske et al.2004) and some adults complain of night wakingsbecause of a full bladder (Pober & Morris 2007). Inone study (n = 20), urinary frequency was found toaffect half of all participants; however, renal func-tion was normal in all (Cherniske et al. 2004).Ultrasound has shown bladder diverticula in indi-viduals with Williams syndrome (Schulman et al.1996; Cherniske et al. 2004); however, an associa-tion with increased urinary frequency has not beenestablished. Nocturia is not expected in this agegroup in the general population. The prevalence byself-report in these Williams syndrome individualssuggests need for further quantification with moredetailed objective measurement. Furthermore, treat-ment of such disorder with vasopressors may helpminimize some of the daytime sleepiness.

While nocturia and periodic limb movements ofsleep might explain a portion of the sleepiness inthese individuals, the possibility of obstructive sleepapnoea also merits consideration. We found thatmore than a fifth of our participants reported theyhad been told they snored. Although snoring is notdiagnostic of sleep apnoea, it is common in sleepapnoea. Furthermore, this population has a highprevalence of cardiovascular anomalies, hyperten-sion, abnormal glucose tolerance and diabetes(Cherniske et al. 2004), all symptomatic of sleepapnoea. In the overall population, these diseases allare associated with a high prevalence and risk ofobstructive sleep apnoea, and they may also beassociated with obstructive sleep apnoea in Williamssyndrome as well.

An underlying sleep disorder may be a contribut-ing factor to the higher prevalence of anxiety andbehavioural disorders in Williams syndrome. Sleepbehaviours may play a role in the broader pheno-typical presentation of Williams syndrome (Mason& Arens 2006). Individuals with Williams syndromeoften have coexistent psychiatric disorders, such asADHD, stress and anxiety, that may be complicatedby disturbed sleep (Stores 2001). Existing researchshows significant overlap between anxiety and sleepin children (Chorney et al. 2008). Adults withADHD are more than likely to have a variety ofsleep problems (Gau et al. 2007). Similar to ourpopulation of adults with Williams syndrome, anactigraphy study of adults with ADHD showed

these individuals to have lower sleep efficiency,longer sleep onset latency and shorter sleep dura-tion than a matched control group of normal adults(Boonstra et al. 2007).

Behaviour problems occur in association withpoorer sleep and higher levels of daytime sleepiness.Sleep problems have been implicated in poordaytime learning and occupational performance, aswell as with higher probabilities of daytime behav-ioural disorders in individuals with ID (Lancioniet al. 1999). Problematic behaviours have beenfound to be associated with sleep disorders in agroup of 205 adults with mental handicaps; theseindividuals scored significantly higher on a majorityof the subscales of the Aberrant Behavior Checklist(Didden & Sigafoos 2001). Although we can notascertain whether behavioural disturbances areassociated with sleep disturbances in the currentstudy, future research is warranted to define thisassociation.

Other neurodevelopmental disorders such asPrader-Willi syndrome, Angelman syndrome,Fragile X syndrome, autism, Asperger syndrome,Rett syndrome and Smith-Magenis syndrome listsleep disturbances as associated features (Stores2001; Walz et al. 2005). However, there has beenlittle work performed on adolescents and adults,with most of the reported studies focusing on child-hood. Sleep parameters measured with actigraphyin adolescents and young adults with autistic disor-der, Asperger syndrome and an unspecified intellec-tual disorder (Oyane & Bjorvatn 2005; Hare et al.2006) suggest individuals with Williams syndromeshare similar sleep patterns with these disorders.These patterns differ from the sleep patterns ofadolescents and young adults without a neurodevel-opmental disorder. In general, the individuals withneurodevelopmental disorders took longer to fallasleep, had poorer sleep efficiency and spent moretime awake after sleep onset. Potential reasons forthese differences are speculative. Many developmen-tal disabilities have clear genetic etiologies, andevidence suggests the potential for different poly-somnographic phenotypes in children with develop-mental disabilities (Harvey & Kennedy 2002).Further, developmental disorders are often associ-ated with psychiatric disturbances, sensory deficitsand immobility issues, as well as with medicationside effects (Stores 2001).




This study has several strengths and weaknesses.Strengths include that this is the first study to lookat sleep in a population of adolescents and adultswith Williams syndrome. We employed both objec-tive and subjective measures to obtain this infor-mation. With actigraphy, we were able tocharacterize sleep–wake patterns over several nightsin the participants’ own environment. This allowedus to document the prevalence of insomnia anddisrupted sleep in these individuals. Shortcomingsof this research were the lack of polysomnographyas a mechanism to evaluate sleep in this popula-tion, the lack of a control group, potential biasassociated with self-report data. Additionally, indi-viduals with Williams syndrome have a strongdesire to please others and give the answer thatthey think others want to hear, which may havebiased results. However, the presence of docu-mented sleep disruption with actigraphy supportsthe validity of self-report of sleep in Williams syn-drome even though the subjective sleep data werecollected 3–4 weeks prior to the wrist actigraphdata.

These findings suggest avenues for futureresearch. First, the high prevalence of sleep disrup-tion found indicates the need for polysomnographyevaluation. Use of polysomnography would provideadditional information on sleep in Williams syn-drome, including measurement of EEG activity,respiratory parameters and leg movements. Second,the use of control subjects with and without devel-opmental disabilities would further provide infor-mation as to the extent that Williams syndromeindividuals have sleep disruption that is similar ordissimilar to other individuals of matched age andgender. Third, future studies could measure behav-ioural correlates and relate these to disordered sleepin Williams syndrome. Finally, defining the sleepcharacteristics of these individuals will providedirection for future studies to improve nighttimesleep and subsequent daytime function in thissyndrome and other related disorders ofneurodevelopment.

Acknowledgement

This study was funded by The Vanderbilt UniversityKennedy Center for Human Development.

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Accepted 16 November 2008




sleep patterns and daytime sleepiness in adolescents and young adults with williams syndrome

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