Paul Linkowski

Quantitative analysis of the 24-hour blood pressure and heart rate patterns in young men.

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.

Sleep disturbance in anxiety disorders

Many patients suffering from the majority of anxiety disorders complain about their sleep by reporting difficulties in initiating and maintaining it. Polysomnographic studies have shown that, in comparison to normal subjects, the sleep of patients with panic disorder is characterized by longer sleep latency, increased time awake and reduced sleep efficiency. Sleep architecture is normal and there are no significant changes in REM sleep measures. Nocturnal panic attacks are non-REM-related events and occur without an obvious trigger in 18–45% of panic disorder patients. Regarding generalized anxiety disorder, the patients complain of ‘trouble sleeping’ in 60–70%, while polysomnography has shown increased sleep latency and decreased sleep continuity measures. The findings in REM sleep and sleep architecture generally do not show any aberration to exist. In patients with obsessive-compulsive disorder (OCD) and post-traumatic stress disorder (PTSD), results from the sleep laboratory do not seem to support the subjective complaints of poor sleep. The early reports of shortened REM latency in OCD could not be replicated by recent studies. A dysregulation of the REM sleep control system has been reported for patients with PTSD. Finally, no significant differences were found in all sleep parameters between social phobia patients and controls.

The first-night effect may last more than one night

The first-night effect in sleep polysomnographic studies is usually considered to last for one night. However, a few observations have indicated that variables associated to rapid eye movement sleep take longer to stabilize. Notwithstanding, current opinion holds that second nights of recording can be used without restriction for research and clinical purposes. The goal of this study was to describe the dynamics of habituation to polysomnography in optimal conditions. Twenty-six young, carefully screened, healthy subjects were recorded in their home for four consecutive full polysomnographies. Repeated measures ANOVA were applied. Between the two first nights, while there were no differences in sleep duration in non-rapid eye movement sleep, marked modifications in corresponding spectral power were observed. The dynamics of adaptation of rapid eye movement sleep appeared to be a process extending up to the fourth night. Similar dynamics in NREMS and REMS homeostasis have been observed in sleep deprivation studies, and it appears that the same mechanisms may be responsible for the FNE. The longer habituation process of REMS in particular has important implications for sleep research in psychiatry.

Altered Sleep Brain Functional Connectivity in Acutely Depressed Patients

Recent evidence suggests that problems in information processing within neural networks may underlie depressive disease. In this study, we investigated whether sleep functional brain networks are abnormally organized during a major depressive episode (MDE). We characterized spatial patterns of functional connectivity by computing the “synchronization likelihood” (SL) of 19 sleep EEG channels in 11 acutely depressed patients [42 (20–51) years] and 14 healthy controls [32.9 (27–42) years]. To test whether disrupting an optimal pattern [“small‐world network” (SWN)] of functional brain connectivity underlies MDE, graph theoretical measures were then applied to the resulting synchronization matrices, and a clustering coefficient (C, measure of local connectedness) and a shortest path length (L, measure of overall network integration) were determined. In the depressed group, the mean SL was lower in the delta, theta and sigma frequency bands. Acutely depressed patients showed a significantly lower path length in the theta and delta frequency bands, whereas the cluster coefficient showed no significant changes. The present study provides further support that sleep functional brain networks exhibit “small‐world” properties. Sleep neuronal functional networks in depressed patients are characterized by a functional reorganization with a lower mean level of global synchronization and loss of SWN characteristics. These results argue for considering an MDE as a problem of neuronal network organization and a problem of information processing. Hum Brain Mapp, 2009.

EEG sleep patterns in twins

The investigation of sleep in twins represents one of the major methods for measuring the genetic contributions to sleep in humans. This paper reviews two twin studies in which the sleep EEG was recorded during three consecutive nights in young monozygotic (MZ) and dizygotic (DZ) male twins. The analyses, based on average values of repeated sleep recordings, indicate that a significant proportion of variance in stages 2, 4, and delta sleep appears to be genetically determined. Genetic influences on rapid‐eye‐movement sleep were found inconclusive, but this conclusion is limited by the relatively small size of the sample studied.

A study of the dynamic interactions between sleep EEG and heart rate variability in healthy young men

OBJECTIVE We investigated the interactions between heart rate variability and sleep electroencephalogram power spectra. METHODS Heart rate and sleep electroencephalogram signals were recorded in 8 healthy young men. Spectral analysis was applied to electrocardiogram and electroencephalogram recordings. Spectral components of RR intervals were studied across sleep stages. The cross-spectrum maximum was determined as well as coherencies, gains and phase shifts between normalized high frequency of RR intervals and all electroencephalographic frequency bands, calculated over the first 3 NREM-REM cycles. RESULTS RR intervals increased from awake to NREM and decreased during REM. Normalized low frequency decreased from awake to NREM and increased during REM while normalized high frequency evolved conversely. Low to high frequency ratio developed in opposition to RR intervals. Coherencies between normalized high frequency and power spectra were high for all bands. The gain was highest for delta band. Phase shift between normalized high frequency and delta differed from zero and modifications in normalized high frequency preceded changes in delta by 41+/-14 degrees. CONCLUSIONS Our study demonstrates that: (1) all electroencephalographic power bands are linked to normalized high frequency; (2) modifications in cardiac vagal activity show predominantly parallel changes and precede changes in delta band by a phase shift corresponding to a lead of 12+/-5 min.

Suicidal behaviour in major depressive illness

ABSTRACT– We investigated past suicidal behaviour and family history of suicide in 713 inpatients with major depressive illness. A familial history of suicide (mainly violent) significantly increased the frequency of violent suicidal behaviour in depressive women; bipolar patients being more affected than unipolars. In depressed men, the presence of suicidal behaviour was not significantly affected by polarity. The occurrence of familial suicide significantly increased the risk of violent suicidal behaviour in male depressed attempters. The present study indicates that a familial history of violent suicide is associated with the presence of violent suicidal behaviour in major depressive patients.

Simultaneous Study of 24-Hour Patterns of Melatonin and Cortisol Secretion in Depressed Patients

The temporal organization of melatonin and cortisol secretion were studied in depressed patients in order to investigate a possible relationship between the secretory patterns of the two hormones. Women who suffered from a primary affective disorder were studied twice as inpatients, the first time during the depressive episode and the second time after amitriptyline treatment and clinical recovery. During both 24-hour studies blood was collected at 1-hour intervals during the day and at 30-min intervals at night. A dissociation of melatonin and cortisol secretory patterns was observed in the 3 patients in whom the two hormones were determined simultaneously. 2 patients exhibited alterations in the circadian rhythm of both hormones during illness. After recovery, however, the melatonin rhythm remained altered but the cortisol rhythm was normalized. Another patient showed a nocturnal melatonin rise and day-night melatonin differences closer to those seen in normal subjects, but she had altered cortisol secretory patterns during depression which normalized after recovery. These results suggest that the melatonin and cortisol rhythms are controlled by different mechanisms.

Cerebrospinal fluid neurophysins in affective illness and in schizophrenia

SummaryWe studied the concentration of neurophysin I ( hNPI) and II (hNPII), the hypothalamo-pituitary carriers of vasopressin and oxytocin, in CSF of depressed and schizophrenic patients and age matched controls. Mean hNPI values were lower and mean hNPII values greater in schizophrenics than in controls. Lower hNPI values were observed in unipolar patients than in controls. In bipolar patients however, higher hNPI values were present. Significantly higher hNPII values were observed in bipolar patients than in controls; no difference was present between unipolars and controls. A positive correlation was observed with age in controls and bipolars for hNPII. These data emphasize the interest of studying the neurohypophysal function in affective illness and in schizophrenia.

EEG sleep patterns in man: a twin study

All-night EEG sleep recording was performed for 3 consecutive nights in 26 pairs of normal male twins (14 monozygotic and 12 dizygotic) in order to investigate genetic components of sleep. The analysis was based on average values of repeated sleep measures and controlled for the effect of cohabitation. Our results indicate that a significant proportion of variance in stages 2, 4 and delta sleep as well as in REM density is genetically determined in man. Genetic influences on stage 1 and REM are strongly confounded by a synchronizing effect of the cohabitational status.