title: Consequences of comorbid sleep apnea in the metabolic syndrome--implications for cardiovascular risk.
abstract: OBJECTIVE
  Metabolic syndrome (MetSyn) increases overall cardiovascular risk. MetSyn is also strongly associated with obstructive sleep apnea (OSA), and these 2 conditions share similar comorbidities. Whether OSA increases cardiovascular risk in patients with the MetSyn has not been investigated. We examined how the presence of OSA in patients with MetSyn affected hemodynamic and autonomic variables associated with poor cardiovascular outcome.
  
  
  METHODS
  Prospective clinical study.
  
  
  METHODS
  We studied 36 patients with MetSyn (ATP-III) divided into 2 groups matched for age and sex: (1) MetSyn+OSA (n = 18) and (2) MetSyn-OSA (n = 18).
  
  
  METHODS
  OSA was defined by an apnea-hypopnea index (AHI) > 15 events/hour by polysomnography. We recorded muscle sympathetic nerve activity (MSNA - microneurography), heart rate (HR), and blood pressure (BP - Finapres). Baroreflex sensitivity (BRS) was analyzed by spontaneous BP and HR fluctuations.
  
  
  RESULTS
  MSNA (34 +/- 2 vs 28 +/- 1 bursts/min, P = 0.02) and mean BP (111 +/- 3 vs. 99 +/- 2 mm Hg, P = 0.003) were higher in patients with MetSyn+OSA versus patients with MetSyn-OSA. Patients with MetSyn+OSA had lower spontaneous BRS for increases (7.6 +/- 0.6 vs 12.2 +/- 1.2 msec/mm Hg, P = 0.003) and decreases (7.2 +/- 0.6 vs 11.9 +/- 1.6 msec/mm Hg, P = 0.01) in BP. MSNAwas correlated with AHI (r = 0.48; P = 0.009) and minimum nocturnal oxygen saturation (r = -0.38, P = 0.04).
  
  
  CONCLUSIONS
  Patients with MetSyn and comorbid OSA have higher BP, higher sympathetic drive, and diminished BRS, compared with patients with MetSyn without OSA. These adverse cardiovascular and autonomic consequences of OSA may be associated with poorer outcomes in these patients. Moreover, increased BP and sympathetic drive in patients with MetSyn+OSA may be linked, in part, to impairment of baroreflex gain.
authors.affiliation: Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil.
authors.forename: Ivani C
authors.initials: IC
authors.lastname: Trombetta
authors.forename: Virend K
authors.initials: VK
authors.lastname: Somers
authors.forename: Cristiane
authors.initials: C
authors.lastname: Maki-Nunes
authors.forename: Luciano F
authors.initials: LF
authors.lastname: Drager
authors.forename: Edgar
authors.initials: E
authors.lastname: Toschi-Dias
authors.forename: Maria Janieire N N
authors.initials: MJ
authors.lastname: Alves
authors.forename: Raffael F
authors.initials: RF
authors.lastname: Fraga
authors.forename: Maria Urbana P B
authors.initials: MU
authors.lastname: Rondon
authors.forename: Maíta G
authors.initials: MG
authors.lastname: Bechara
authors.forename: Geraldo
authors.initials: G
authors.lastname: Lorenzi-Filho
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Negrão
mesh_terms: D000328:Adult; D017704:Baroreflex; D001794:Blood Pressure; D002318:Cardiovascular Diseases / Q000209:etiology*; D016022:Case-Control Studies; D015331:Cohort Studies; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D024821:Metabolic Syndrome / Q000150:complications* / Q000378:metabolism / Q000503:physiopathology*; D008875:Middle Aged; D010101:Oxygen Consumption; D012307:Risk Factors; D020181:Sleep Apnea, Obstructive / Q000150:complications* / Q000378:metabolism / Q000503:physiopathology*; D014664:Vasodilation