title: Abnormal secretion of melatonin and cortisol in relation to sleep disturbances in children with Williams syndrome.
abstract: OBJECTIVE
  A high rate of sleep disturbances has been reported in individuals with Williams syndrome (WS) but the underlying aetiology has yet to be identified. Melatonin and cortisol levels display circadian rhythmicity and are known to affect and regulate sleep/wake patterns. The current study examined the levels of these two endocrine markers and explored a possible relationship with sleep patterns in children with WS.
  
  
  METHODS
  Twenty-five children with WS and 27 typically developing age- and gender-matched comparison children were recruited. Saliva was collected from each child at three time points: 4-6 pm, before natural bedtime, and after awakening. The levels of salivary melatonin and cortisol were analysed by specific enzyme-linked immunoassays. Sleep patterns were examined using actigraphy and the Children's Sleep Habit Questionnaire.
  
  
  RESULTS
  The WS group had shallower drops in cortisol and less pronounced increase in melatonin at bedtime compared to the controls. Furthermore, they also had significantly higher levels of cortisol before bedtime.
  
  
  CONCLUSIONS
  Increased bedtime cortisol and less pronounced rise in melatonin levels before sleep may play a role in the occurrence of sleep disturbances, such as delayed sleep onset, observed in children with WS. As both markers play a significant role in our circadian rhythm and sleep/wake cycle, it is necessary to examine sleep using multi-system analysis.
authors.affiliation: School of Science and Technology, Middlesex University, London, UK.
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Sniecinska-Cooper
authors.affiliation: Eric Leonard Kruse Foundation for Health Research, Glasgow, UK.
authors.forename: Ray Kruse
authors.initials: RK
authors.lastname: Iles
authors.affiliation: School of Science and Technology, Middlesex University, London, UK.
authors.forename: Stephen Andrew
authors.initials: SA
authors.lastname: Butler
authors.affiliation: School of Science and Technology, Middlesex University, London, UK.
authors.forename: Huw
authors.initials: H
authors.lastname: Jones
authors.affiliation: School of Science and Technology, Middlesex University, London, UK; Department of Electronic and Electrical Engineering, University College London, London, UK.
authors.forename: Richard
authors.initials: R
authors.lastname: Bayford
authors.affiliation: Department of Psychology and Human Development, Institute of Education, University of London, London, UK. Electronic address: d.dimitriou@ioe.ac.uk.
authors.forename: Dagmara
authors.initials: D
authors.lastname: Dimitriou
mesh_terms: D056044:Actigraphy; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D002940:Circadian Rhythm / Q000502:physiology; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism*; D008297:Male; D008550:Melatonin / Q000378:metabolism*; D012893:Sleep Wake Disorders / Q000175:diagnosis / Q000209:etiology / Q000378:metabolism*; D011795:Surveys and Questionnaires; D018980:Williams Syndrome / Q000150:complications* / Q000378:metabolism* / Q000503:physiopathology
chemical_list: D008550:Melatonin; D006854:Hydrocortisone
keywords: Cortisol; Developmental disorders; Endocrine sleep markers; Melatonin; Williams syndrome