Age-related trend for blood pressure circadian rhythm in normotensive healthy subjects: estimates provided by the clinospectror method.

: The present study investigates how blood pressure (BP) circadian rhythm (CR) changes in its rhythmic properties as a function of chronological age in normotensive healthy subjects (NHS). The age-related trend for BP CR was investigated via the Clinospectror method, a periodic-linear analysis of regression for rhythmic parameters. The study was performed on 437 NHS (219 males and 218 females, ranging in age from 1 year to 102 years), who were monitored in their 24-h BP via a noninvasive automated recorder. An age-related trend was detected for the three properties of BP CR, i.e., mesor (M), amplitude (A) and acrophase (cent). Such a trend was positive for M and A, and negative for cent. According to the clinospectrometric formula, the BP CR can be classified as a "dianaclinous rhythm", i.e., a rhythm which increases in its oscillatory level and extent with advancing years. The documented age-related trend for the rhythmic properties suggests that the biological clock which regulates the BP CR in human beings undergoes a resetting of its mechanisms of tonic, amplitude and phasic modulation as a function of chronological age. The readjustment of the pressure clock may be regarded as one of the physiological features which characterize the aging process in human beings.