title: A 4-year prospective follow-up study of childhood OSA and its association with BP.
abstract: BACKGROUND
  Childhood OSA is a prevalent condition associated with raised BP as documented in cross-sectional studies. This study aimed to determine whether baseline or change in OSA severity was associated with ambulatory BP at 4-year follow-up.
  
  
  METHODS
  Children who participated in our previous OSA prevalence research were invited to undergo a repeat overnight sleep study and 24-h ambulatory BP monitoring in this 4-year follow-up study. BP parameters of subjects with differing baseline OSA severity, that is, obstructive apnea-hypopnea index (OAHI) < 1/h, 1 to 5/h, and > 5/h, were compared. Overweight and normal-weight children were analyzed separately.
  
  
  RESULTS
  One hundred eighty-five of 306 subjects (60%) were included in the analysis, of whom 58 were overweight at baseline. Linear increasing trends of wake systolic BP (SBP), wake diastolic BP (DBP), and sleep SBP z scores at follow-up were found across groups of increasing baseline OSA severity in the normal weight but not in the overweight subgroup. After adjusting for BMI z score, baseline OAHI was independently associated with all BP z scores at follow-up but not associated with changes in BP z scores across 4 years. On the other hand, change in OAHI was independently associated with sleep SBP and DBP z scores at follow-up and with changes in sleep SBP and DBP z scores across 4 years.
  
  
  CONCLUSIONS
  This study provides longitudinal data as additional proof that childhood OSA is associated with elevated BP independent of obesity.
authors.affiliation: Department of Pediatrics, Department of Psychiatry. Electronic address: albertmli@cuhk.edu.hk.
authors.forename: Albert M
authors.initials: AM
authors.lastname: Li
authors.affiliation: Department of Pediatrics, Department of Psychiatry.
authors.forename: Chun T
authors.initials: CT
authors.lastname: Au
authors.affiliation: Department of Pediatrics, Department of Psychiatry.
authors.forename: Crystal
authors.initials: C
authors.lastname: Ng
authors.affiliation: Department of Pediatrics, Department of Psychiatry.
authors.forename: Hugh S
authors.initials: HS
authors.lastname: Lam
authors.affiliation: Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors.forename: Crover K W
authors.initials: CKW
authors.lastname: Ho
authors.affiliation: Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors.forename: Yun K
authors.initials: YK
authors.lastname: Wing
mesh_terms: D000293:Adolescent; D001794:Blood Pressure / Q000502:physiology*; D018660:Blood Pressure Monitoring, Ambulatory; D002648:Child; D002940:Circadian Rhythm / Q000502:physiology; D015897:Comorbidity; D005260:Female; D005500:Follow-Up Studies; D006723:Hong Kong; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008137:Longitudinal Studies; D008297:Male; D009765:Obesity / Q000503:physiopathology; D017286:Polysomnography; D011446:Prospective Studies; D012720:Severity of Illness Index; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology*