Age-associated alteration of sympatho-vagal balance in a female population assessed through the tone–entropy analysis

Abstract

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.

Evaluation of diabetic neuropathy using the tone-entropy analysis, a noninvasive method to estimate the autonomic nervous function

“…1. The distribution was similar to the ones reported previously (1,2,16,18). The patients with retinopathy or nephropathy tended to have higher tone and lower range or when inter-individual comparison is attempted (10,19,23).…”

“…The patients with retinopathy or nephropathy tended to have higher tone and lower range or when inter-individual comparison is attempted (10,19,23). In this context, the tone-entropy (TE) analysis was introduced as an alternative method to evaluate the autonomic function (1,16,18). In this analysis, the variation of the R-R interval was used to calculate the tone and the entropy as defined previously (2, 18).…”

“…In this analysis, the variation of the R-R interval was used to calculate the tone and the entropy as defined previously (2, 18). Oida et al indicated that the tone was influenced by the autonomic nerve activity while the entropy depended on the balance between the sympathetic and the parasympathetic activity (1,16). From the clinical point of view, the TE analysis has a potential advantage over the spectral analysis because it enables a direct comparison of the autonomic activity between individuals even under respiratory noises (1,18).…”

“…Oida et al indicated that the tone was influenced by the autonomic nerve activity while the entropy depended on the balance between the sympathetic and the parasympathetic activity (1,16). From the clinical point of view, the TE analysis has a potential advantage over the spectral analysis because it enables a direct comparison of the autonomic activity between individuals even under respiratory noises (1,18). In the present study, to evaluate the usefulness of the TE analysis in the diagnosis of diabetic neuropathy, we compared the TE analysis with the NCV in patients with DM.…”

“…The TE data were obtained after at least 10-min rest at the spine position. The electrocardiogram (FPC-4301; Fukuda Denshi Co., Tokyo, Japan) was recorded for 5 min, converted into digital signal at a sampling rate of 10 kHz, and analyzed using a software developed by Oida et al (1,18). The tone and the entropy were calculated with the following formulae (18);…”