Spectral analysis of heart rate indicates reduced baroreceptor-related heart rate variability in elderly persons

Spectral analysis of the cardiac interbeat interval was used to examine baroreceptor-related supine and standing heart rate variability (HRV) in young (less than 40 years of age) and elderly (greater than 60 years of age) healthy volunteers. Heart rates and blood pressures were examined also. When supine, average heart rate, systolic and diastolic blood pressure, and HRV for the young volunteers were 66.5 bpm, 113.0/64.3 mmHg, and 5.74 log units of relative power, respectively. The same values for the elderly group were 65.4 bpm, 126.3/74.0 mmHg, and 4.43 log units. Statistical analysis revealed that, compared to the young volunteers, supine elderly volunteers had similar heart rates, higher blood pressures, and lower baroreceptor HRV. There was little change in blood pressure in either group upon standing. However, upon standing, heart rate increased 17.7 bpm and baroreceptor HRV increased to 6.58 (+ 14.6%) in the younger volunteers. This was significantly different from the elderly volunteers, whose heart rate increased by only 10.9 bpm and their HRV to 4.72 (+ 6.5%). These results indicate that much of the reduction in HRV in old age results from decreases in baroreceptor modulation of heart rate. In addition, the difference between young and old persons is greatest in the standing position because elderly individuals exhibit less recruitment of baroreceptor activity with postural change.