title: Sleep-disordered breathing does not affect nocturnal dipping, as assessed by pulse transit time, in preschool children: evidence for early intervention to prevent adverse cardiovascular effects?
abstract: OBJECTIVE
  Sleep-disordered breathing (SDB) is associated with reduced nocturnal dipping of blood pressure (BP) and sleep disruption in adults, and these features confer an increased risk of cardiovascular events. As SDB prevalence in children peaks during the preschool years, we investigated nocturnal dipping and sleep fragmentation in preschool children with SDB.
  
  
  METHODS
  Children (3-5 years; n=163) grouped by obstructive apnoea hypopnoea index (OAHI): control, no snoring history and OAHI ≤1 event/h; primary snoring, OAHI ≤1 event/h; mild SDB, >1-≤5 events/h; moderate-severe SDB, >5 events/h. Pulse transit time (PTT), an inverse continuous indicator of BP changes, and heart rate (HR) during total sleep time and the first period of rapid eye movement (REM), non-REM (NREM)1/2 and NREM3/4 sleep were expressed as percentage change from wake before sleep onset. The sleep fragmentation index (SFI) was calculated as the number of sleep stage transitions or awakenings per hour of sleep.
  
  
  RESULTS
  There were no group differences in the change in PTT or HR from wake to total sleep time or to individual sleep stages or in the proportion of children in the quartile with the smallest change in PTT during total sleep. Children with moderate-severe SDB had higher SFI than primary snoring (PS) or mild SDB groups (p<0.05 for both) and controls (p=0.07).
  
  
  CONCLUSIONS
  In contrast to adults, nocturnal dipping is preserved in young children with SDB, despite increased sleep fragmentation. As there is evidence that nocturnal dipping is similarly preserved at the school age, childhood may pose a window of opportunity for resolution of SDB when the cardiovascular effects are less marked.
authors.affiliation: The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia.
authors.forename: Lauren C
authors.initials: LC
authors.lastname: Nisbet
authors.affiliation: The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia; Melbourne Children's Sleep Centre, Monash Children's Programme, Monash Medical Centre, Melbourne, Victoria, Australia.
authors.forename: Gillian M
authors.initials: GM
authors.lastname: Nixon
authors.affiliation: The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia.
authors.forename: Stephanie R
authors.initials: SR
authors.lastname: Yiallourou
authors.affiliation: The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia.
authors.forename: Sarah N
authors.initials: SN
authors.lastname: Biggs
authors.affiliation: The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia; Melbourne Children's Sleep Centre, Monash Children's Programme, Monash Medical Centre, Melbourne, Victoria, Australia.
authors.forename: Margot J
authors.initials: MJ
authors.lastname: Davey
authors.affiliation: Discipline of Psychological Sciences, University of Melbourne, Melbourne, Victoria, Australia.
authors.forename: John
authors.initials: J
authors.lastname: Trinder
authors.affiliation: The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia.
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Walter
authors.affiliation: The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia. Electronic address: rosemary.horne@monash.edu.
authors.forename: Rosemary S C
authors.initials: RS
authors.lastname: Horne
mesh_terms: D001794:Blood Pressure / Q000502:physiology; D002318:Cardiovascular Diseases / Q000175:diagnosis* / Q000503:physiopathology* / Q000517:prevention & control; D002675:Child, Preschool; D002940:Circadian Rhythm / Q000502:physiology; D061345:Early Medical Intervention; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D017286:Polysomnography; D063177:Pulse Wave Analysis; D012307:Risk Factors; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000503:physiopathology*; D012892:Sleep Deprivation / Q000175:diagnosis / Q000503:physiopathology / Q000517:prevention & control; D012894:Sleep Stages / Q000502:physiology; D013223:Statistics as Topic; D014739:Victoria
keywords: Blood pressure; Children; Heart rate; Nocturnal dipping; Obstructive sleep apnoea; Sleep fragmentation; Sleep-disordered breathing; Snoring