title: Obstructive Sleep Apnea Impairs Postexercise Sympathovagal Balance in Patients with Metabolic Syndrome.
abstract: OBJECTIVE
  The attenuation of heart rate recovery after maximal exercise (ΔHRR) is independently impaired by obstructive sleep apnea (OSA) and metabolic syndrome (MetS). Therefore, we tested the hypotheses: (1) MetS + OSA restrains ΔHRR; and (2) Sympathetic hyperactivation is involved in this impairment.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  We studied 60 outpatients in whom MetS had been newly diagnosed (ATP III), divided according to apnea-hypopnea index (AHI) ≥ 15 events/h in MetS + OSA (n = 30, 49 ± 1.7 y) and AHI < 15 events/h in MetS - OSA (n = 30, 46 ± 1.4 y). Normal age-matched healthy control subjects (C) without MetS and OSA were also enrolled (n = 16, 46 ± 1.7 y).
  
  
  METHODS
  Polysomnography, microneurography, cardiopulmonary exercise test.
  
  
  RESULTS
  We evaluated OSA (AHI - polysomnography), muscle sympathetic nerve activity (MSNA - microneurography) and cardiac autonomic activity (LF = low frequency, HF = high frequency, LF/HF = sympathovagal balance) based on spectral analysis of heart rate (HR) variability. ΔHRR was calculated (peak HR minus HR at first, second, and fourth minute of recovery) after cardiopulmonary exercise test. MetS + OSA had higher MSNA and LF, and lower HF than MetS - OSA and C. Similar impairment occurred in MetS - OSA versus C (interaction, P < 0.01). MetS + OSA had attenuated ΔHRR at first, second, and at fourth minute than did C, and attenuated ΔHRR at fourth minute than did MetS - OSA (interaction, P < 0.001). Compared with C, MetS - OSA had attenuated ΔHRR at second and fourth min (interaction, P < 0.001). Further analysis showed association of the ΔHRR (first, second, and fourth minute) and AHI, MSNA, LF and HF components (P < 0.05 for all associations).
  
  
  CONCLUSIONS
  The attenuation of heart rate recovery after maximal exercise is impaired to a greater degree where metabolic syndrome (MetS) is associated with moderate to severe obstructive sleep apnea (OSA) than by MetS with no or mild or no OSA. This is at least partly explained by sympathetic hyperactivity.
authors: Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil.
authors: Felipe X
authors: FX
authors: Cepeda
authors: Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil.
authors: Edgar
authors: E
authors: Toschi-Dias
authors: Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil.
authors: Cristiane
authors: C
authors: Maki-Nunes
authors: Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil.|School of Physical Education and Sports, University of São Paulo, São Paulo, Brazil.
authors: Maria Urbana P B
authors: MU
authors: Rondon
authors: Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil.
authors: Maria Janieire N N
authors: MJ
authors: Alves
authors: Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil.
authors: Ana Maria F W
authors: AM
authors: Braga
authors: Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil.
authors: Daniel G
authors: DG
authors: Martinez
authors: Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil.
authors: Luciano F
authors: LF
authors: Drager
authors: Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil.
authors: Geraldo
authors: G
authors: Lorenzi-Filho
authors: Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil.|School of Physical Education and Sports, University of São Paulo, São Paulo, Brazil.
authors: Carlos E
authors: CE
authors: Negrao
authors: Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil.|Universidade Nove de Julho (UNINOVE), São Paulo, Brazil.
authors: Ivani C
authors: IC
authors: Trombetta
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D024821:Metabolic Syndrome / Q000150:complications* / Q000503:physiopathology*; D008875:Middle Aged; D017286:Polysomnography; D020181:Sleep Apnea, Obstructive / Q000150:complications* / Q000503:physiopathology*; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D014630:Vagus Nerve / Q000502:physiology*
keywords: heart rate recovery; heart rate variability; muscle sympathetic nerve activity