GENDER DIFFERENCES IN AGING ALTERATION OF CARDIAC SYMPATHOVAGAL BALANCE ASSESED THROUGH THE TONE-ENTROPY ANALYSIS

Abstract

Age-associated alterations of autonomic sympathovagal balance are intensively investigated by a various analyses on heart rate variability; however, there is little information on gender effects in aging process. PURPOSE The purpose of this study was to elucidate the gender differences of sympathovagal alteration comparing with our previous male study through the tone-entropy (T-E) analysis. METHODS Seventeen-three female subjects (40–79 yr) participated in the study. The subjects were classified into two age groups: middle-aged, 40 ≤ age ≤ 59 (40–50); and old-aged, 60 ≤ age ≤ 79; (60–70). Electrocardiographic data were collected at rest for 10 min. Examinations were carried out through two indexes, the tone and the entropy, which represent the sympathovagal balance and the total autonomic efferent ctivity, respectively (Oida et al., 1997). RESULTS The tone was high [−0.056±0.011 (40–50), −0.028±0.003 (60–70), (p < 0.05)], and the entropy, low [3.39±0.12 (40–50), 3.09±0.08 bit (60–70), (p < 0.05)] in old-aged population compared with middle-aged one. These age-related alterations of the tone and the entropy consistently followed the identical curvilinear pathway in two-dimensional space (T-E space) by the tone in ordinate and the entropy in abscissa, as found for the previous male study. Furthermore, the present study clearly demonstrated a slight difference between male and female. The tone positioned delicately lower in middle-aged female than the age-matched male population [−0.039±0.003 (male), −0.056±0.011 (female), P < 0.05], although the difference disappeared for old-aged one. CONCLUSION The results suggest that the vagal predominance would be impaired with age for female as the same way as male population. Interestingly, a delicate difference between female and male was appreciated for the younger group although disappeared for the older population. Thus, T-E analysis could describe not only an aging alteration but also a delicate distinction between male and female.