Objective: This study examines changes in the broad time structure (chronome) of blood pressure (BP) as a function of age.
Design: This is an observational study.
Setting: The study was conducted at the Chronobiology Laboratories of the University oi Minnesota, Minneapolis, Minnesota.
Participants: Seventy-two individuals 12 to 106 years of age provided a 7-day record of BP measured indirectly with an ambulatory monitor, mostly at 15-60-minute intervals.
Main outcome measures: Amplitudes in least squares spectra at frequencies of 1 to 7 cycles per week and 1 to 8 cycles per day were analyzed by linear regression as a function of age. A two-way analysis of variance for subjects classified in four age groups tested for any variance transposition from the circadian (about-daily) to the infradian (frequency lower than one cycle per day) and/or to the ultradian (frequency higher than one cycle per day) domain.
Results: The decreasing circadian BP amplitude with age is accompanied by an increase in infradian and ultradian prominence. The day-to-day variability in circadian characteristics also increases with age.
Conclusion: A variance transposition from the circadian to the neighboring ultradian and infradian domains characterizes the elderly human BP chronome, as a new, technically implementable biological, rather than chronological, gauge of human aging.