[en] INTRODUCTION: Sleep is a complex phenomenon characterized by important modifications throughout life and by changes of autonomic cardiovascular control. Aging is associated with a reduction of the overall heart rate variability (HRV) and a decrease of complexity of autonomic cardiac regulation. The aim of our study was to evaluate the HRV complexity using two entropy-derived measures, Shannon Entropy (SE) and Corrected Conditional Entropy (CCE), during sleep in young and older subjects. METHODS: A polysomnographic study was performed in 12 healthy young (21.1+/-0.8 years) and 12 healthy older subjects (64.9+/-1.9 years). After the sleep scoring, heart period time series were divided into wake (W), Stage 1-2 (S1-2), Stage 3-4 (S3-4) and REM. Two complexity indexes were assessed: SE(3) measuring the complexity of a distribution of 3-beat patterns (SE(3) is higher when all the patterns are identically distributed and it is lower when some patterns are more likely) and CCE(min) measuring the minimum amount of information that cannot be derived from the knowledge of previous values. RESULTS: Across the different sleep stages, young subjects had similar RR interval, total variance, SE(3) and CCE(min). In the older group, SE(3) and CCE(min) were reduced during REM sleep compared to S1-2, S3-4 and W. Compared to young subjects, during W and sleep the older subjects showed a lower RR interval and reduced total variance as well as a significant reduction of SE(3) and CCE(min). This decrease of entropy measures was more evident during REM sleep. CONCLUSION: Our study indicates that aging is characterized by a reduction of entropy indices of cardiovascular variability during wake/sleep cycle, more evident during REM sleep. We conclude that during aging REM sleep is associated with a simplification of cardiac control mechanisms that could lead to an impaired ability of the cardiovascular system to react to cardiovascular adverse events.
Malliani A, Pagani M, Montano N, Mela GS, (1998) Sympathovagal balance: a reappraisal. Circulation 98 (23): 2640-3.
Malliani A, Montano N, (2002) Heart rate variability as a clinical tool. Ital Heart J 3 (8): 439-45.
Akselrod S, Gordon D, Ubel FA, Shannon DC, Berger AC, et al. (1981) Power spectrum analysis of heart rate fluctuation: a quantitative probe of beat-to-beat cardiovascular control. Science 10; 213 (4504): 220-2.
Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology (1996) Heat rate variability. Standards of measurement, physiological interpretation and clinical use. Circulation 93: 1043.
Montano N, Cogliati C, Dias da Silva VJ, Gnecchi-Ruscone T, Malliani A, (2001) Sympathetic rhythms and cardiovascular oscillations. Auton Neurosci 20; 90 (1-2): 29-34.
Montano N, Porta A, Cogliati C, Costantino G, Tobaldini E, et al. (2009) Heart rate variability explored in the frequency domain: a tool to investigate the link between heart and behaviour. Neurosci Biobehav Rev 33: 71-80.
Porta A, Guzzetti S, Furlan R, Gnecchi-Ruscone T, Montano N, et al. (2007) Complexity and Nonlinearity in Short-Term Heart Period Variability: Comparison of Methods Based on Local Nonlinear Prediction. IEEE Trans Biomed Eng 54: 94-106.
Porta A, Guzzetti S, Montano N, Furlan R, Pagani M, et al. (2001) Entropy, entropy rate and pattern classification as tools to typify complexity in short heart period variability series. IEEE Trans Biomed Eng 48: 1282-1291.
Porta A, Gnecchi-Ruscone T, Tobaldini E, Guzzetti S, Furlan R, et al. (2007) Progressive decrease of heart period variability entropy-based complexity during graded head-up tilt. J Appl Physiol 103: 1143-9.
Porta A, Faes L, Masé M, D'Addio G, Pinna GD, et al. (2007) An integrated approach based on uniform quantization for the evaluation of complexity of short-term heart period variability: application to 24 h Holter recordings in healthy and heart failure humans. Chaos 17: 015117.
Richman JS, Moorman JR, (2000) Physiological time-series analysis using approximate entropy and sample entropy. Am J Physiol Heart Circ Physiol 278: H2039-49.
Pincus S, (1995) Approximate entropy (ApEn) as a complexity measure. Chaos 5: 110-117.
Clariá F, Vallverdú M, Baranowski R, Chojnowska L, Caminal P, (2008) Heart rate variability analysis based on time-frequency representation and entropies in hypertrophic cardiomyopathy patients. Physiol Meas 29: 401-16.
Huikuri HV, Mäkikallio TH, Perkiömäki J, (2003) Measurement of heart rate variability by methods based on nonlinear dynamics. J Electrocardiol 36 (Suppl): 95-9.
Voss A, Kurths J, Kleiner HJ, Witt A, Wessel N, et al. (1996) The application of methods of non-linear dynamics for the improved and predictive recognition of patients threatened by sudden cardiac death. Cardiovasc Res 31: 419-33.
Lipsitz LA, (1995) Age-related changes in the "complexity" of cardiovascular dynamics: A potential marker of vulnerability to disease. Chaos 5: 102-109.
Pikkujämsä S M, Mäkikallio T H, Sourander LB, Räihä IJ, Puukka P, et al. (1999) Cardiac interbeat interval dynamics from childhood to senescence: comparison of conventional and new measures based on fractals and chaos theory. Circulation 100: 393-399.
Vigo DE, Guinjoan SM, Scaramal M, Siri LN, Cardinali DP, (2005) Wavelet transform shows age-related changes of heart rate variability within independent frequency components. Auton Neurosci 123: 94-100.
Wu GQ, Arzeno NM, Shen LL, Tang DK, Zheng DA, et al. (2009) Chaotic signatures of heart rate variability and its power spectrum in health, aging and heart failure. PLoS One 4: e4323.
Kuo TB, Lin T, Yang CC, Li CL, Chen CF, et al. (1999) Effect of aging on gender differences in neural control of heart rate. Am J Physiol 277: H2233-9.
Bonnemeier H, Richardt G, Potratz J, Wiegand VK, Brandes A, et al. (2003) Circadian profile of cardiac autonomic nervous modulation in healthy subjects: differing effects of aging and gender on HRV. J Cardiovasc. Electrophysiol 14 (8): 800-2.
Lipsitz LA, Goldberger AL, (1992) Loss of 'complexity' and aging. Potential applications of fractals and chaos theory to senescence. JAMA 267 (13): 1806-9.
Lipsitz LA, Mietus J, Moody GB, Goldberger AL, (1990) Spectral characteristics of heart rate variability before and during postural tilt: relations to aging and risk of syncope. Circulation 81: 1803-1810.
Kaplan DT, Furman MI, Pincus SM, Ryan SM, Lipsitz LA, et al. (1991) Aging and the complexity of cardiovascular dynamics. Biophys J 59: 945-9.
Caples SM, Garcia-Touchard A, Somers VK, (2007) Sleep-disordered breathing and cardiovascular risk. Sleep 30 (3): 291-303.
Somers VK, White DP, Amin R, Abraham WT, Costa F, et al. (2008) Sleep apnea and cardiovascular disease: an American Heart Association/American College Of Cardiology Foundation Scientific Statement from the American Heart Association Council for High Blood Pressure Research Professional Education Committee, Council on Clinical Cardiology, Stroke Council, and Council On Cardiovascular Nursing. In collaboration with the National Heart, Lung, and Blood Institute National Center on Sleep Disorders Research (National Institutes of Health). Circulation 118 (10): 1080-111.
Bonnet MH, (2009) Evidence for the pathophysiology of insomnia. Sleep 32 (4): 441-2.
Monti A, Medigue C, Nedelcoux H, Escourrou P, (2002) Autonomic control of the cardiovascular system during sleep in normal subjects. Eur J Appl Physiol 87: 174-81.
Trinder J, Kleiman J, Carrington M, Smith S, Breen S, et al. (2001) Autonomic activity during human sleep as a function of time and sleep stage. J Sleep Res 10 (4): 253-64.
Vanoli E, Adamson PB, Ba-Lin, Pinna GD, Lazzara R, et al. (1995) Heart rate variability during specific sleep stages. A comparison of healthy subjects with patients after myocardial infarction. Circulation 1 (91): 1918-22.
Berlad I I, Shlitner A, Ben-Haim S, Lavie P, (1993) Power spectrum analysis and heart rate variability in Stage 4 and REM sleep: evidence for state-specific changes in autonomic dominance. J Sleep Res 2: 88-90.
Legramante JM, Marciani MG, Placidi F, Aquilani S, Romigi A, et al. (2003) Sleep-related changes in baroreflex sensitivity and cardiovascular autonomic modulation. J Hypertens 21: 1555-61.
Vigo DE, Dominguez J, Guinjoan SM, Scaramal M, Ruffa E, et al. (2010) Nonlinear analysis of heart rate variability within independent frequency components during the sleep-wake cycle. Auton Neurosci 19 (154): 84-8.
Virtanen I, Ekholm E, Polo-Kantola P, Huikuri H, (2007) Sleep stage dependent patterns of nonlinear heart rate dynamics in postmenopausal women. Auton Neurosci 31 (134): 74-80.
Fell J, Mann K, Röschke J, Gopinathan MS, (2000) Nonlinear analysis of continuous ECG during sleep II. Dynamical measures. Biol Cybern 82: 485-91.
Beckers F, Verheyden B, Aubert AE, (2006) Aging and nonlinear heart rate control in a healthy population. Am J Physiol Heart Circ Physiol 290: H2560-70.
Crasset V, Mezzetti S, Antoine M, Linkowski P, Degaute JP, et al. (2002) Effects of aging and cardiac denervation on heart rate variability during sleep. Circulation 103: 84-8.
Brandenberger G, Viola AU, Ehrhart J, Charloux A, Geny B, et al. (2003) Age-related changes in cardiac autonomic control during sleep. J Sleep Res 12: 173-80.
Schumann AY, Bartsch RP, Penzel T, Ivanov PCh, Kantelhardt JW, (2010) Aging effects on cardiac and respiratory dynamics in healthy subjects across sleep stages. Sleep 33 (7): 943-55.
Rechtschaffen A, Kales A, (1968) A Manual of Standardized Terminology, Techniques and Scoring System for Sleep Stages of Human Subjects. Los Angeles, CA UCLA Brain Information Service, Brain Research Institute.
Porta A, D'addio G, Guzzetti S, Lucini D, Pagani M, (2004) Testing the presence of non stationarities in short heart rate variability series. Computers in Cardiology 31: 645-648.
Goff EA, Nicholas CL, Malaweera AS, Simonds AK, Trinder J, et al. (2010) The influence of age on heart rate variability during morning wakefulness. Clin Auton Res. 20 (3): 175-82.
Goldberger AL, Amaral LA, Hausdorff JM, Ivanov P, Peng CK, et al. (2002) Fractal dynamics in physiology: alterations with disease and aging. Proc Natl Acad Sci U S A 99 (Suppl): 12466-2472.
Huikuri HV, Mäkikallio TH, Peng CK, Goldberger AL, Hintze U, et al. (2000) Fractal correlation properties of R-R interval dynamics and mortality in patients with depressed left ventricular function after an acute myocardial infarction. Circulation 101 (1): 47-53.
Lavery CE, Mittleman MA, Cohen MC, Muller JE, Verrier RL, (1997) Nonuniform nighttime distribution of acute cardiac events: a possible effect of sleep states. Circulation 96 (10): 3321-7.
