Variability in the arterial pressure of newborns as compared to that of adults and old men.
The systolic and diastolic blood pressure was monitored on healthy subjects of different ages, spanning from newborns (24-48 hs old, to elderly age (70-80 years old). Each subject was monitored for 15 minutes, and the pressure values collected every minute. This protocol allowed a statistical evaluation of both inter- and intraindividual variabilities among and within different class ages. As expected, increasing age is paralleled by a marked increase in the average values of systolic blood pressure; the trend of variabilities around the average, however, as traced by standard deviations, is just the opposite: a marked decrease going from newborns to adults is accompanied--in most cases--by a statistically significant difference in the same direction also between adults and old men. This can be rationalized, in the light of recent findings on the role of deterministic chaos in the functional behaviour of complex biological systems, in terms of decreased functional flexibility characteristic of the aging process.