title: Complexity Variability Assessment of Nonlinear Time-Varying Cardiovascular Control.
abstract: The application of complex systems theory to physiology and medicine has provided meaningful information about the nonlinear aspects underlying the dynamics of a wide range of biological processes and their disease-related aberrations. However, no studies have investigated whether meaningful information can be extracted by quantifying second-order moments of time-varying cardiovascular complexity. To this extent, we introduce a novel mathematical framework termed complexity variability, in which the variance of instantaneous Lyapunov spectra estimated over time serves as a reference quantifier. We apply the proposed methodology to four exemplary studies involving disorders which stem from cardiology, neurology and psychiatry: Congestive Heart Failure (CHF), Major Depression Disorder (MDD), Parkinson's Disease (PD), and Post-Traumatic Stress Disorder (PTSD) patients with insomnia under a yoga training regime. We show that complexity assessments derived from simple time-averaging are not able to discern pathology-related changes in autonomic control, and we demonstrate that between-group differences in measures of complexity variability are consistent across pathologies. Pathological states such as CHF, MDD, and PD are associated with an increased complexity variability when compared to healthy controls, whereas wellbeing derived from yoga in PTSD is associated with lower time-variance of complexity.
authors.affiliation: Massachusetts General Hospital/Harvard Medical School, Boston, MA, USA.|Department of Information Engineering and Bioengineering and Robotics Research Centre "E. Piaggio", School of Engineering, University of Pisa, Italy.
authors.forename: Gaetano
authors.initials: G
authors.lastname: Valenza
authors.affiliation: School of Computer Science and Electronic Engineering, University of Essex, Colchester, UK.
authors.forename: Luca
authors.initials: L
authors.lastname: Citi
authors.affiliation: Masira Research Institute, School of Medicine, Universidad de Santander, Bucaramanga, Colombia.
authors.forename: Ronald G
authors.initials: RG
authors.lastname: Garcia
authors.affiliation: Nell Hodgson Woodruff School of Nursing, Emory University, Atlanta, GA, USA.
authors.forename: Jessica Noggle
authors.initials: JN
authors.lastname: Taylor
authors.affiliation: Massachusetts General Hospital/Harvard Medical School, Boston, MA, USA.|University of Rome "Tor Vergata", Rome, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Toschi
authors.affiliation: Massachusetts General Hospital/Harvard Medical School, Boston, MA, USA.|Politecnico di Milano, Milan, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Barbieri
mesh_terms: D000328:Adult; D002319:Cardiovascular System / Q000503:physiopathology*; D016022:Case-Control Studies; D003865:Major Depressive Disorder / Q000503:physiopathology*; D004562:Electrocardiography; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008955:Models, Cardiovascular; D017711:Nonlinear Dynamics; D010300:Parkinson Disease / Q000503:physiopathology*; D013313:Stress Disorders, Post-Traumatic / Q000503:physiopathology*; D055815:Young Adult