Age-associated alteration of sympatho-vagal balance in a female population assessed through the tone-entropy analysis.
Through our recent studies on heart rate variability (Oida et al. J Appl Physiol 82:1794-1801, 1997; J Gerontol 54A:M219-M224, 1999a; Acta Physiol Scand 165:129-134, 1999b; Acta Physiol Scand 165:421-422, 1999c), we discover that autonomic functions could be assessed quantitatively in time domain by the tone-entropy (T-E) methodology, where the tone represents sympatho-vagal balance, and the entropy, autonomic regulatory activity. The purpose of this study was then to elucidate an age-associated alteration of sympatho-vagal balance in a female population through this T-E method. ECG R-R time intervals at rest were acquired on 10 min for 73 female subjects. Ageing influence was examined by comparisons between two groups: middle-aged group (40-50), (51.5 +/- 0.7 year, n = 28) and old-aged (60-70), (69.5 +/- 0.8 year, n = 45)]. Evaluated tone: [-0.058 +/- 0.011 (40-50), and 0.027 +/- 0.003 (60-70) (P < 0.01)], and entropy: [3.46 +/- 0.11 (40-50), and 3.06 +/- 0.08 bit (60-70) (P<0.01)]. The result showed that the tone was high and the entropy was low in the old-aged compared with the middle-aged group. When the result was plotted in two-dimensional T-E space, it revealed a curvi-linear relation between the tone and the entropy, consistent with our previous studies on pharmacological blockades, on heart recovery after dynamic exercise and on a male ageing. In conclusion, the result suggested that the sympatho-vagal balance altered or the vagal predominance was impaired with age significantly in this female population. Interestingly, comparing with corresponding male, the female had better autonomic functions.
Amano
Masari
M
Laboratory of Applied Physiology, Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 6068501, Japan.
Oida
Eiichi
E
Moritani
Toshio
T
D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology*; D000465:Algorithms; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D004562:Electrocardiography / Q000379:methods*; D019277:Entropy; D005260:Female; D006321:Heart / Q000294:innervation* / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D008955:Models, Cardiovascular; D015233:Models, Statistical; D013564:Sympathetic Nervous System / Q000502:physiology*; D014630:Vagus Nerve / Q000502:physiology*