title: Are Complexity Metrics Reliable in Assessing HRV Control in Obese Patients During Sleep?
abstract: Obesity is associated with cardiovascular mortality. Linear methods, including time domain and frequency domain analysis, are normally applied on the heart rate variability (HRV) signal to investigate autonomic cardiovascular control, whose imbalance might promote cardiovascular disease in these patients. However, given the cardiac activity non-linearities, non-linear methods might provide better insight. HRV complexity was hereby analyzed during wakefulness and different sleep stages in healthy and obese subjects. Given the short duration of each sleep stage, complexity measures, normally extracted from long-period signals, needed be calculated on short-term signals. Sample entropy, Lempel-Ziv complexity and detrended fluctuation analysis were evaluated and results showed no significant differences among the values calculated over ten-minute signals and longer durations, confirming the reliability of such analysis when performed on short-term signals. Complexity parameters were extracted from ten-minute signal portions selected during wakefulness and different sleep stages on HRV signals obtained from eighteen obese patients and twenty controls. The obese group presented significantly reduced complexity during light and deep sleep, suggesting a deficiency in the control mechanisms integration during these sleep stages. To our knowledge, this study reports for the first time on how the HRV complexity changes in obesity during wakefulness and sleep. Further investigation is needed to quantify altered HRV impact on cardiovascular mortality in obesity.
authors.affiliation: DEIB, Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano, Italy.
authors.forename: Ramona
authors.initials: R
authors.lastname: Cabiddu
authors.affiliation: Cardiopulmonary Physiotherapy Laboratory, Federal University of São Carlos, São Carlos, São Paulo, Brazil.
authors.forename: Renata
authors.initials: R
authors.lastname: Trimer
authors.affiliation: Cardiopulmonary Physiotherapy Laboratory, Federal University of São Carlos, São Carlos, São Paulo, Brazil.
authors.forename: Audrey
authors.initials: A
authors.lastname: Borghi-Silva
authors.affiliation: DEIB, Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Migliorini
authors.affiliation: Cardiopulmonary Physiotherapy Laboratory, Federal University of São Carlos, São Carlos, São Paulo, Brazil.
authors.forename: Renata G
authors.initials: RG
authors.lastname: Mendes
authors.affiliation: Sleep Institute of São Carlos, São Paulo, Brazil.
authors.forename: Antonio D
authors.initials: AD
authors.lastname: Oliveira
authors.affiliation: Sleep Institute of São Carlos, São Paulo, Brazil.
authors.forename: Fernando S M
authors.initials: FS
authors.lastname: Costa
authors.affiliation: DEIB, Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano, Italy.
authors.forename: Anna M
authors.initials: AM
authors.lastname: Bianchi
mesh_terms: D000328:Adult; D000465:Algorithms; D001341:Autonomic Nervous System / Q000503:physiopathology; D015992:Body Mass Index; D016022:Case-Control Studies; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods*; D009765:Obesity / Q000503:physiopathology*; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D012890:Sleep / Q000502:physiology*; D014851:Wakefulness / Q000502:physiology