title: Age-related trend in circadian rhythm of electrocardiographic sinusal R-R intervals in clinically healthy subjects.
abstract: 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.
authors.affiliation: Department of Clinical Sciences, University of Rome La Sapienza, Rome, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Cugini
authors.forename: R
authors.initials: R
authors.lastname: De Rosa
authors.forename: T
authors.initials: T
authors.lastname: De Laurentis
authors.forename: K
authors.initials: K
authors.lastname: Tamura
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D002648:Child; D002940:Circadian Rhythm; D015716:Electrocardiography, Ambulatory; D005260:Female; D006329:Heart Conduction System / Q000502:physiology*; D006339:Heart Rate; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D012016:Reference Values