title: Obstructive sleep apnea and heart rate variability in male patients with metabolic syndrome: cross-sectional study.
abstract: BACKGROUND
  Obstructive sleep apnea (OSA) is often accompanied by the metabolic syndrome. Because both conditions are associated with depressed heart rate variability (HRV) separately, our aim was to study whether co-morbid OSA is associated with more reduced HRV in male patients with the metabolic syndrome.
  
  
  METHODS
  In this cross-sectional study, 35 men (age, 57±11 years) with the metabolic syndrome (according to International Diabetes Federation criteria) were included. OSA severity was defined by the apnea-hypopnea index (AHI). HRV was assessed by 24-hr ambulatory electrocardiographic monitoring. Standard deviation of all normal-to-normal RR intervals (SDNN), the high frequency power (HFP), and the ratio of low- to high-frequency power (LF/HF) were measured.
  
  
  RESULTS
  There were 14, 6, and 8 cases of severe (AHI ≥30/hr), moderate (15/hr≤AHI <30/hr), and mild (5/hr ≤AHI <15/hr) OSA, respectively. Seven patients had no OSA. Patients with mild-moderate or severe OSA had reduced SDNN and HFP values compared to those without OSA. Increasing OSA severity was associated significantly with lower daytime LF/HF ratio [standardized β regression coefficient (β)=-0.362, P=0.043] and higher night/day LF/HF ratio (β=0.377, P=0.023) after controlling for age, duration of diabetes, and severity of metabolic syndrome.
  
  
  CONCLUSIONS
  Co-morbid OSA is associated with decreased overall HRV, parasympathetic loss, and impaired diurnal pattern of sympathovagal balance that may further increase the cardiovascular vulnerability of male patients with the metabolic syndrome. The role of the HRV analysis in the risk assessment of these patients warrants further studies.
authors: 1 Institute of Behavioural Sciences, Sleep Medicine Team, Semmelweis University Faculty of Medicine , Budapest, Hungary .
authors: Orsolya
authors: O
authors: Véber
authors: Zsofia
authors: Z
authors: Lendvai
authors: Katalin Zsuzsanna
authors: KZ
authors: Ronai
authors: Andrea
authors: A
authors: Dunai
authors: Rezso
authors: R
authors: Zoller
authors: Anett Virag
authors: AV
authors: Lindner
authors: Csilla Zita
authors: CZ
authors: Turányi
authors: Julia Luca
authors: JL
authors: Szocs
authors: Katalin
authors: K
authors: Keresztes
authors: Adam Gyula
authors: AG
authors: Tabák
authors: Marta
authors: M
authors: Novak
authors: Miklos Z
authors: MZ
authors: Molnar
authors: Istvan
authors: I
authors: Mucsi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D015716:Electrocardiography, Ambulatory; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D024821:Metabolic Syndrome / Q000150:complications / Q000453:epidemiology* / Q000503:physiopathology*; D008875:Middle Aged; D017286:Polysomnography; D020181:Sleep Apnea, Obstructive / Q000150:complications / Q000453:epidemiology* / Q000503:physiopathology*; D055815:Young Adult