CIRCADIAN RHYTHM IN BLOOD PRESSURE IN NEWBORNS AND ADULTS

Objective: The aim of the study was the analysis of long lasting blood pressure monitoring in premature babies and newborns, lasting 14 to 45 days and in adult people monitored for seven day using ambulatory blood pressure monitoring to describe the circadian rhythm. Design and method: Blood pressure and heart rate were monitored automatically for 14 to 45 days, mostly at 30 minutes intervals from a total of 86 premature babies. We examined 145 healthy subjects using seven-day ambulatory blood pressure monitoring (TM-2421 A and D, Japan). From the newborn babies blood pressure data and heart rate data and data from 7-day ambulatory blood pressure monitoring were analyzed using the power spectral density function, which was computed from the autocorrelation functions using the Hanning spectral window. We also evaluated blood pressure mean values for 24 hours and the blood pressure deeping. Results: Our data showed in adults, using comparison of deeping of circadian (24 hours) and of the week component (168 hours) of systolic and diastolic blood pressure, large prominence of circadian component in systolic and diastolic blood pressure. The week variation in blood pressure in adult healthy subjects are present and are very small. Long lasting monitoring in newborns showed slow oscillations in systolic and diastolic blood pressure with a different period between 5 to 10 days and in blood pressure in all newborns. An identical period in heart rate, systolic and diastolic blood pressure was found in 31%. The peak of 24-hour periodicity in heart rate was found in 50% of newborns, in systolic and diastolic blood pressure only in 43%. The peak of 24-hour periodicity was always smaller than those found with week rhythm. Mean power spectra revealed a significant peak (p < 0.05) at 0.16 cycles per day in systolic and diastolic blood pressure. Conclusions: In newborns we have found in blood pressure in deeping large prominence of the week rhythm component (168 h) in comparison to circadian variation (24 h). In adult healthy subjects the circadian rhythm is most prominent in blood pressure oscillations and week rhythm shows small oscillations.