title: A comparative scale of autonomic function with age through the tone-entropy analysis on heart period variation.
abstract: Tremendous numbers of heart rate variability studies have aimed to elucidate age-associated alterations of autonomic function in the past decades. However, the studies, far from clarifying ageing mechanisms, fell into confusion by a lack of common scales. The purpose of this study is to show a possibility to establish a comparative scale of autonomic function through a method, tone-entropy (T-E) analysis on heart period variation, whose validity has been already examined on typical physiological cases (Oida et al. in J Appl Physiol 82:1794-1801, 1997; Oida et al. in J Gerontol 54A:M219-M224, 1999a; Oida et al. in Acta Physiol Scand 165:129-134, 1999b; Oida et al. in Acta Physiol Scand 165:421-422, 1999c; Amano et al. in Eur J Appl Physiol 94:602-610, 2005). In this study, 276 subjects from teens to seventies were examined at rest by T-E analysis together with conventional time and frequency domain analyses. The tone (negativity represents vagal predominance) became significantly high [-0.174 +/- 0.026 (teens) to -0.024 +/- 0.004 (seventies), P < 0.05 for one-way ANOVA], and the entropy (total autonomic activity), significantly low [4.40 +/- 0.12 (teens) to 2.90 +/- 0.09 bit (seventies), P < 0.05] with advancing age. The result, plotted in 2-D T-E space, showed that the ageing traced a curvi-linear relation from right-bottom to left-top, and was consistent with previously studied typical physiological cases. The conventional analyses showed almost the same autonomic reduction as T-E did, but failed in detecting delicate alteration of autonomic balance. The results, showing that autonomic activity reduced in both pathways impairing vagal predominance significantly with ageing, suggested a possibility to assess autonomic function in 2-D T-E space in a comparative way.
authors.affiliation: Laboratory of Applied Physiology, Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan.
authors.forename: Masari
authors.initials: M
authors.lastname: Amano
authors.forename: Eiichi
authors.initials: E
authors.lastname: Oida
authors.forename: Toshio
authors.initials: T
authors.lastname: Moritani
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D004562:Electrocardiography / Q000379:methods*; D019277:Entropy; D006321:Heart / Q000294:innervation* / Q000502:physiology; D006339:Heart Rate; D006801:Humans; D008875:Middle Aged