The 24-h profile of plasma ACTH and cortisol levels was determined in 18 men suffering from major depressive illness (8 with unipolar depression and 10 with bipolar depression) as well as in 7 age-matched normal men. Blood was sampled every 15 min. The circadian variation and episodic fluctuations were analyzed for each individual profile. Both unipolar and bipolar depressed patients had higher 24-h mean cortisol levels (P less than 0.01) than normal men, but no significant difference in 24-h mean ACTH level was found. The nadir of cortisol secretion occurred almost 3 h earlier in older normal subjects and patients with unipolar depression, regardless of age, than in younger normal subjects. This shift paralleled a similar advance of the ACTH nadir. Early timing of the quiescent period of ACTH-cortisol secretion was also found in several patients with bipolar depression, but did not reach significance at the group level. The hypercortisolism in the depressed patients was associated with an increase in the magnitude, but not the number, of cortisol secretory episodes. About 90% of the cortisol pulses could be related to a concomitant ACTH pulse in normal subjects as well as in both groups of depressed patients. However, concomitant ACTH and cortisol pulses were less correlated in magnitude in depressed patients than in normal subjects. These results indicate that major depressive illness is associated with disturbances of pituitary-adrenal function. The early timing of the nadir of ACTH-cortisol secretion suggests that disorders of circadian time keeping may characterize major endogenous depression.

To characterize the normal nycterohemeral blood pressure and heart rate profiles and to delineate the relative roles of sleep and circadian rhythmidty, we performed 24-hour ambulatory blood pressure monitoring with simultaneous polygraphic sleep recording in 31 healthy young men investigated in a standardized physical and social environment Electroencephalographic sleep recordings were performed during 4 consecutive nights. Blood pressure and heart rate were measured every 10 minutes for 24 hours starting in the morning preceding the fourth night of recording. Sleep quality was not significantly altered by ambulatory blood pressure monitoring. A best-fit curve based on the periodogram method was used to quantify changes in blood pressure and heart rate over the 24-hour cycle. The typical blood pressure and heart rate patterns were bimodal with a morning acrophase (around 10:00 AM), a small afternoon nadir (around 3:00 PM), an evening acrophase (around 8:00 PM), and a profound nocturnal nadir (around 3:00 AM). The amplitude of the nycterohemeral variations was largest for heart rate, intermediate for diastolic blood pressure, and smallest for systolic blood pressure (respectively, 19.9%, 14.1%, and 10.9% of the 24-hour mean). Before awakening, a significant increase in blood pressure and heart rate was already present Recumbency and sleep accounted for 65-75% of the nocturnal decline in blood pressure, but it explained only 50% of the nocturnal decline in heart rate. Thus, the combined effects of postural changes and the wake-sleep transition are the major factors responsible for the 24-hour rhythm in blood pressure. In contrast, the 24-hour rhythm of heart rate may reflect an endogenous circadian rhythm, amplified by the effect of sleep. We conclude that modulatory factors different from those controlling nycterohemeral changes in blood pressure influence the 24-hour variation in heart rate. (Hypertension 1991;18:199-210) R ecent progress in medical technology has seen the development of fully automatic portable noninvasive blood pressure recorders that reliably monitor blood pressure and heart rate over periods of 24 hours and longer. The use of ambulatory blood pressure monitoring has improved our understanding of the remarkably wide intraindividual and interindividual variability that characterizes blood pressure in humans. 1-2 It has From the Hypertension Clinic (J-P.D., P.van de B. already been demonstrated that adverse effects of high blood pressure on the heart were better correlated with mean 24-hour blood pressure levels than with casual blood pressure readings. 3-4 It is also well established that, under normal conditions, blood pressure is higher during the daytime than during the nighttime. 5-6 Whether these day-night variations are entirely due to changes in activity or are partially related to an endogenous circadian rhythm that persists under constant conditions is still a matter of controversy. Although some studies indicated that the level of physical activity has a predominant role in the nycte...

Fifteen recumbent young health volunteers underwent 24-h beat-to-beat blood pressure (BP) and interbeat interval (IBI) recordings to explore the effects of wake and polygraphically recorded sleep on the nyctohemeral variations in the spectral frequency components of BP and IBI and in the arterial baroreflex sensitivity (BRS), independent of the confounding effects of changes in posture and physical activity. Spectral analysis of BP and IBI provided markers of sympathetic and vagal controls and of arterial BRS. When falling asleep, the low-frequency (LF) BP and IBI components showed a marked decrease while there was a clear-cut increase in the high-frequency (HF) IBI component. In contrast, only a slight nighttime rapid eye movement-related arterial BRS increase was observed. The final morning awakening induced a pronounced decrease in arterial BRS and the HF IBI component while there was a marked rise in the LF BP component. Hence, a clear 24-h variation in sympathetic and vagal tone but not in arterial BRS persists, independent of changes in activity and position.