Age-related trend in circadian rhythm of electrocardiographic sinusal R-R intervals in clinically healthy subjects
Cugini, P.; De Rosa, R.; De Laurentis, T.; Tamura, K.
La Clinica Terapeutica 153(2): 93-97
2002
ISSN/ISBN: 0009-9074 PMID: 12078346 Document Number: 545755
It is a clinical observation that human HR shows a tendency to bradycardia with advancing age. In addition, there is experimental evidence that heart rate (HR) shows a circadian rhythm (CR) in healthy humans. Because of this background, the present study is devoted to investigate how the CR of the electrocardiographic sinusal R-R intervals (SRRI) changes its properties as a function of chronological age in healthy humans. The study was performed on 170 clinically healthy Japanese, ranging in age from 12 to 83 years (mean age +/- SD = 43 +/- 15 years), who were monitored in their electrocardiogram over the day-night span. An opposite age-related trend was detected for two properties of SRRI CR, i.e., mesor (positive trend) and amplitude (negative trend). Accordingly, the SRRI CR can be classified as an "amphiclinous rhythm", i.e., a rhythm in which the cardiac interbeat duration shows a progressive increase of its daily mean value along with a progressive deamplification of its oscillatory extent. Furthermore, the rhythm is characterized by a progressive anticipation in time of its oscillatory maximum of duration with advancing age. The findings suggest that the biological clocks regulating the HR CR in human beings undergo a resetting of their mechanisms of tonic, amplitude and phasic modulation as a function of age. The clock-mediated readjustment of the HR CR may be regarded as one of the mechanisms for explaining the bradycardia that is associated with the aging process in human beings.