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Aging reduces complexity of heart rate variability assessed by conditional entropy and symbolic analysis

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Abstract

Increasing age is associated with a reduction in overall heart rate variability as well as changes in complexity of physiologic dynamics. The aim of this study was to verify if the alterations in autonomic modulation of heart rate caused by the aging process could be detected by Shannon entropy (SE), conditional entropy (CE) and symbolic analysis (SA). Complexity analysis was carried out in 44 healthy subjects divided into two groups: old (n = 23, 63 ± 3 years) and young group (n = 21, 23 ± 2). It was analyzed SE, CE [complexity index (CI) and normalized CI (NCI)] and SA (0V, 1V, 2LV and 2ULV patterns) during short heart period series (200 cardiac beats) derived from ECG recordings during 15 min of rest in a supine position. The sequences characterized by three heart periods with no significant variations (0V), and that with two significant unlike variations (2ULV) reflect changes in sympathetic and vagal modulation, respectively. The unpaired t test (or Mann–Whitney rank sum test when appropriate) was used in the statistical analysis. In the aging process, the distributions of patterns (SE) remain similar to young subjects. However, the regularity is significantly different; the patterns are more repetitive in the old group (a decrease of CI and NCI). The amounts of pattern types are different: 0V is increased and 2LV and 2ULV are reduced in the old group. These differences indicate marked change of autonomic regulation. The CE and SA are feasible techniques to detect alteration in autonomic control of heart rate in the old group.

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Acknowledgments

This work was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (06/52860-0 to A.C.M.T. and 05/54838-9 to A.M.C.), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (PDEE/1228/08-0 to A.C.M.T.) and grant number PRIN 2007 to N.M.

Conflict of interest

The authors declare that they have no conflict of interest related to the publication of this manuscript.

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Authors and Affiliations

  1. Cardiovascular Physiotherapy Laboratory, Nucleus of Research in Physical Exercise, Physiotherapy Department, Federal University of São Carlos, Via Washington Luiz, km 235, CP: 676, São Carlos, São Paulo, 13565-905, Brazil

    Anielle C. M. Takahashi, Ruth C. Melo, Robison J. Quitério, Ester da Silva, Audrey Borghi-Silva & Aparecida M. Catai

  2. Department of Technologies for Health, Galeazzi Orthopaedic Institute, University of Milan, Milan, Italy

    Alberto Porta

  3. School of Arts, Sciences and Humanities, University of São Paulo, São Paulo, Brazil

    Ruth C. Melo

  4. UNESP-Univ Estadual Paulista, Marília, São Paulo, Brazil

    Robison J. Quitério

  5. Faculty of Health Sciences, Methodist University of Piracicaba, Piracicaba, São Paulo, Brazil

    Ester da Silva

  6. Department of Clinical Sciences, Internal Medicine II, L. Sacco Hospital, University of Milan, Milan, Italy

    Eleonora Tobaldini & Nicola Montano

Authors
  1. Anielle C. M. Takahashi
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  2. Alberto Porta
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  3. Ruth C. Melo
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  8. Nicola Montano
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  9. Aparecida M. Catai
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Correspondence to Anielle C. M. Takahashi.

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Takahashi, A.C.M., Porta, A., Melo, R.C. et al. Aging reduces complexity of heart rate variability assessed by conditional entropy and symbolic analysis. Intern Emerg Med 7, 229–235 (2012). https://doi.org/10.1007/s11739-011-0512-z

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  • DOI: https://doi.org/10.1007/s11739-011-0512-z

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