title: Maturation of heart rate and blood pressure variability during sleep in term-born infants.
abstract: OBJECTIVE
  Abnormal blood pressure control is implicated in the sudden infant death syndrome (SIDS). However, no data exist on normal development of blood pressure control during infancy. This study assessed maturation of autonomic control of blood pressure and heart rate during sleep within the first 6 months of life.
  
  
  METHODS
  Term infants (n = 31) were studied longitudinally at 2-4 weeks, 2-3 months, and 5-6 months postnatal age.
  
  
  METHODS
  Infants underwent daytime polysomnography at each age studied. Blood pressure and heart rate were recorded during quiet (QS) and active (AS) sleep in undisturbed baseline and head-up tilt conditions.
  
  
  RESULTS
  Autonomic control was assessed using spectral indices of blood pressure and heart rate variability (BPV and HRV) in ranges of low frequency (LF, reflecting sympathetic + parasympathetic activity) and high frequency (HF, parasympathetic activity), total power (LF+HF), and LF/HF ratio (sympathovagal balance). With increasing postnatal age and predominantly during QS, HRV-LF, HRV-HF, and HRV total power increased, while HRV-LF/HF decreased. BPV-LF/HF also decreased with postnatal age. All changes were evident in both baseline and head-up tilt conditions. BPV-LF and BPV total power during tilts were markedly reduced in QS versus AS at each age.
  
  
  CONCLUSIONS
  In sleeping infants, sympathetic vascular modulation of the circulation decreases with age, while parasympathetic control of heart rate is strengthened. These normative data will aid in the early identification of conditions where autonomic function is impaired, such as in SIDS.
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.forename: Scott A
authors.initials: SA
authors.lastname: Sands
authors.forename: Adrian M
authors.initials: AM
authors.lastname: Walker
authors.forename: Rosemary S C
authors.initials: RS
authors.lastname: Horne
mesh_terms: D000367:Age Factors; D001341:Autonomic Nervous System / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D002657:Child Development / Q000502:physiology*; D004562:Electrocardiography / Q000379:methods / Q000706:statistics & numerical data; D004569:Electroencephalography / Q000379:methods / Q000706:statistics & numerical data; D004576:Electromyography / Q000379:methods / Q000706:statistics & numerical data; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn / Q000502:physiology*; D008137:Longitudinal Studies; D008297:Male; D017286:Polysomnography / Q000379:methods / Q000706:statistics & numerical data; D012016:Reference Values; D012890:Sleep / Q000502:physiology*