title: Prevalence of hypertension and circadian blood pressure variations in patients with obstructive sleep apnoea-hypopnoea syndrome.
abstract: OBJECTIVE
  To investigate the prevalence of hypertension and circadian blood pressure (BP) variations in patients with obstructive sleep apnoea-hypopnoea syndrome (OSAHS).
  
  
  METHODS
  Patients referred to a sleep clinic underwent polysomnography with measurement of BP at four time points. They were classified into four groups (control, and mild, moderate or severe sleep apnoea) using the apnoea-hypopnoea index (AHI). Circadian variation was assessed using night-time to daytime mean BP (R(N/D)) and morning to evening mean BP (R(M/E)) ratios.
  
  
  RESULTS
  Hypertension was significantly more common in patients with OSAHS (50.5%) than in controls (30.4%). AHI was positively correlated with hypertension after controlling for related confounders. Mean BP values at all four time points rose with increasing AHI. The increase in night-time and morning values was more pronounced than the increase in daytime and evening values in patients with OSAHS, resulting in loss of the normal BP diurnal rhythm. The R(N/D) and R(M/E) ratios increased with increasing AHI. Daytime BP was significantly correlated with AHI and the lowest oxygen saturation value.
  
  
  CONCLUSIONS
  OSAHS was shown to be an independent risk factor for hypertension. It was also associated with loss of the normal BP diurnal rhythm.
authors.affiliation: Respiratory Department, Tianjin Medical University General Hospital, Tianjin, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Graduate School, Tianjin Medical University, Tianjin, China.
authors.forename: Caili
authors.initials: C
authors.lastname: Li
authors.affiliation: Respiratory Department, Tianjin Medical University General Hospital, Tianjin, China.
authors.forename: Liting
authors.initials: L
authors.lastname: Feng
authors.affiliation: Respiratory Department, Tianjin Medical University General Hospital, Tianjin, China Division of Pulmonary and Critical Care Medicine, Duke University Medical Center, Durham, NC, USA zyyhxkfj@126.com.
authors.forename: Jing
authors.initials: J
authors.lastname: Feng
authors.affiliation: Respiratory Department, Tianjin Medical University General Hospital, Tianjin, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Cao
authors.affiliation: Respiratory Department, Tianjin Medical University General Hospital, Tianjin, China.
authors.forename: Baoyuan
authors.initials: B
authors.lastname: Chen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure; D001795:Blood Pressure Determination; D002681:China / Q000453:epidemiology; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000453:epidemiology* / Q000209:etiology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D015995:Prevalence; D012307:Risk Factors; D012891:Sleep Apnea Syndromes / Q000150:complications / Q000453:epidemiology* / Q000503:physiopathology; D020181:Sleep Apnea, Obstructive / Q000150:complications / Q000453:epidemiology* / Q000503:physiopathology
keywords: Obstructive sleep apnoea–hypopnoea syndrome; apnoea–hypopnoea index; blood pressure; circadian variation; hypertension; lowest oxygen saturation