title: Effect of age on complexity and causality of the cardiovascular control: comparison between model-based and model-free approaches.
abstract: The proposed approach evaluates complexity of the cardiovascular control and causality among cardiovascular regulatory mechanisms from spontaneous variability of heart period (HP), systolic arterial pressure (SAP) and respiration (RESP). It relies on construction of a multivariate embedding space, optimization of the embedding dimension and a procedure allowing the selection of the components most suitable to form the multivariate embedding space. Moreover, it allows the comparison between linear model-based (MB) and nonlinear model-free (MF) techniques and between MF approaches exploiting local predictability (LP) and conditional entropy (CE). The framework was applied to study age-related modifications of complexity and causality in healthy humans in supine resting (REST) and during standing (STAND). We found that: 1) MF approaches are more efficient than the MB method when nonlinear components are present, while the reverse situation holds in presence of high dimensional embedding spaces; 2) the CE method is the least powerful in detecting age-related trends; 3) the association of HP complexity on age suggests an impairment of cardiac regulation and response to STAND; 4) the relation of SAP complexity on age indicates a gradual increase of sympathetic activity and a reduced responsiveness of vasomotor control to STAND; 5) the association from SAP to HP on age during STAND reveals a progressive inefficiency of baroreflex; 6) the reduced connection from HP to SAP with age might be linked to the progressive exploitation of Frank-Starling mechanism at REST and to the progressive increase of peripheral resistances during STAND; 7) at REST the diminished association from RESP to HP with age suggests a vagal withdrawal and a gradual uncoupling between respiratory activity and heart; 8) the weakened connection from RESP to SAP with age might be related to the progressive increase of left ventricular thickness and vascular stiffness and to the gradual decrease of respiratory sinus arrhythmia.
authors.affiliation: Department of Biomedical Sciences for Health, University of Milan, Milan, Italy ; Galeazzi Orthopedic Institute, Milan, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Porta
authors.affiliation: Department of Physics and BIOtech, University of Trento, Trento, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Faes
authors.affiliation: Gruppo Ospedaliero San Donato Foundation, Milan, Italy ; Department of Electronics Information and Bioengineering, Politecnico di Milano, Milan, Italy.
authors.forename: Vlasta
authors.initials: V
authors.lastname: Bari
authors.affiliation: Department of Electronics Information and Bioengineering, Politecnico di Milano, Milan, Italy ; Department of Anesthesia and Intensive Care, Humanitas Clinical and Research Center, Rozzano, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Marchi
authors.affiliation: Humanitas Clinical and Research Center, Rozzano, Italy.
authors.forename: Tito
authors.initials: T
authors.lastname: Bassani
authors.affiliation: BIOtech, Department of Industrial Engineering, University of Trento, Trento, Italy ; IRCS PAT-FBK, Trento, Italy.
authors.forename: Giandomenico
authors.initials: G
authors.lastname: Nollo
authors.affiliation: Department of Physiotherapy, Federal University of São Carlos, São Carlos, São Paulo State, Brazil.
authors.forename: Natália Maria
authors.initials: NM
authors.lastname: Perseguini
authors.affiliation: Department of Physiotherapy, Federal University of São Carlos, São Carlos, São Paulo State, Brazil.
authors.forename: Juliana
authors.initials: J
authors.lastname: Milan
authors.affiliation: Department of Physiotherapy, Federal University of São Carlos, São Carlos, São Paulo State, Brazil.
authors.forename: Vinícius
authors.initials: V
authors.lastname: Minatel
authors.affiliation: Department of Physiotherapy, Federal University of São Carlos, São Carlos, São Paulo State, Brazil.
authors.forename: Audrey
authors.initials: A
authors.lastname: Borghi-Silva
authors.affiliation: Department of Physiotherapy, Federal University of São Carlos, São Carlos, São Paulo State, Brazil.
authors.forename: Anielle C M
authors.initials: AC
authors.lastname: Takahashi
authors.affiliation: Department of Physiotherapy, Federal University of São Carlos, São Carlos, São Paulo State, Brazil.
authors.forename: Aparecida M
authors.initials: AM
authors.lastname: Catai
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D062186:Arterial Pressure / Q000502:physiology*; D017704:Baroreflex / Q000502:physiology; D005260:Female; D006321:Heart / Q000502:physiology*; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D017711:Nonlinear Dynamics; D011187:Posture / Q000502:physiology; D012119:Respiration; D055815:Young Adult