Relationship between resting augmentation index and spontaneous cardiac baroreflex sensitivity during handgrip exercise in postmenopausal women

Abstract

The stiffening of the conductance arteries is a hallmark of ageing and increases drastically after menopause. Therefore, the augmentation index (AIx), a surrogate for arterial stiffness, could be related to the decline in baroreflex sensitivity. We sought to investigate the relationship between resting AIx and spontaneous cardiac baroreflex sensitivity (cBRS) during handgrip exercise in ageing women. Thirteen young women (YW: 24±5 years; 24±2 kg/m2) and nine postmenopausal women (PMW: 60±5 years; 26±3 kg/m2) underwent the protocol, which consisted of 10 min of supine resting followed by 3 min of static handgrip exercise at 40% of the maximal voluntary force. The AIx was provided by the aortic pressure waveform and cBRS was calculated using the sequence technique, and vagal activity was accessed via heart rate variability using the root mean square of successive differences (RMSSD) index. Resting AIx was higher in PMW compared to YW (YW: 8±10%; PMW: 23±8%; P<0.01), while the cBRS (YW: 16±12 ms/mmHg; PMW: 10±5 ms/mmHg; P=0.08) and RMSSD (YW: 46±35 ms; PMW: 34±12 ms; P=0.26) were similar in YW and PMW. At rest, there was no significant (P>0.05) relationship between the AIx and cBRS in YW and PMW. However, in PMW, a negative (slope=-0.22) and strong (r=-0.70; P=0.03) relationship was observed between AIx and cBRS for the increment of blood pressure during the handgrip exercise. The stiffening of the arterial tree is one possible mechanism to explain the decrease of spontaneous cardiac baroreflex sensitivity during exercise in postmenopausal women.

Figure 1. Spontaneous cardiac baroreflex sensitivity (cBRS) at rest and during handgrip exercise of young women and post-menopausal women. The box represents the mean value. Two-way ANOVA was used for analyses with the statistical significance set to P≤0.05.

Figure 2. Relationship between arterial stiffness and cardiac baroreflex sensitivity. The black lines are the regression lines, and the dotted lines are the confidence intervals of the association between augmentation index (AIx) adjusted for 75 heartbeats per minute and cardiac baroreflex sensitivity (cBRS). Blue circles represent young women, and green squares represent postmenopausal women. Pearson correlation was used for analyses with the statistical significance set to P≤0.05.