EFFECTS OF AGING ON BLOOD-PRESSURE VARIABILITY IN RESTING CONDITIONS

The objective of this study was to determine the effect of aging on be at-to-beat blood pressure and pulse interval variability in resting co nditions and to determine the effect of aging on the sympathetic and v agal influence on the cardiovascular system by power spectral analysis of blood pressure and pulse interval. We studied three groups of heal thy, normotensive subjects: young (10 to 15 years, n=16), adult (20 to 40 years, n=16), and elderly (70 to 90 years, n=25). Beat-to-beat blo od pressure was measured by Finapres during 20 minutes supine and 10 m inutes standing. Overall systolic and diastolic blood pressures and pu lse interval variability were determined as SD and as coefficient of v ariation. Also, relative powers of the mid-frequency (0.08 to 0.12 Hz) and high-frequency bands (0.15 to 0.40 Hz) were determined by spectra l analysis. In these subjects no differences in blood pressure variabi lity (either as SD or coefficient of variation) were found between age groups, except for the coefficient of variation of standing diastolic blood pressure, which decreased with aging. Pulse interval variabilit y decreased with aging. Power of the mid-frequency band of systolic an d diastolic blood pressures was markedly decreased in the elderly, esp ecially in the standing position. Power of the high-frequency band of pulse interval was also decreased in the elderly. Baroreflex sensitivi ty calculated by fast Fourier transformation spectral analysis was dec reased in the elderly subjects compared with the younger groups. In co nclusion, we found no change in the overall variability of blood press ure with aging. Mid-frequency spectral power of blood pressure and mid - and high-frequency spectral powers of pulse interval variability wer e decreased in the elderly. These results suggest that aging does not merely influence the magnitude of blood pressure and pulse interval va riability but causes a complex rearrangement of the variability patter n by changes in neurocardiovascular regulation.