Biomedical subjects

P Linkowski

Publications and source records attributed to P Linkowski.

At least 19 recordsLinked to original sources

PubMed2006

The link between cardiac autonomic activity and sleep delta power is altered in men with sleep apnea-hypopnea syndrome.

We hypothesize that sleep apnea-hypopnea alters interaction between cardiac vagal modulation and sleep delta EEG. Sleep apnea-hypopnea syndrome (SAHS) is related to cardiovascular complications in men. SAHS patients show higher sympathetic activity than normal subjects. In healthy men, non-rapid eye movement (NREM) sleep is associated with cardiac vagal influence, whereas rapid eye movement (REM) sleep is linked to cardiac sympathetic activity. Interaction between cardiac autonomic modulation and delta sleep EEG is not altered across a life span nor is the delay between appearances of modifications in both signals. Healthy controls, moderate SAHS, and severe SAHS patients were compared across the first three NREM-REM cycles. Spectral analysis was applied to ECG and EEG signals. High frequency (HF) and low frequency (LF) of heart rate variability (HRV), ratio of LF/HF, and normalized (nu) delta power were obtained. A coherency analysis between HF(nu) and delta was performed, as well as a correlation analysis between obstructive apnea index (AI) or hypopnea index (HI) and gain, coherence, or phase shift. HRV components were similar between groups. In each group, HF(nu) was larger during NREM, while LF(nu) predominated across REM and wake stages. Coherence and gain between HF(nu) and delta decreased from controls to severe SAHS patients. In SAHS patients, the delay between modifications in HF(nu) and delta did not differ from zero. AI and HI correlated negatively with coherence, while HI correlated negatively with gain only. Apneas-hypopneas affect the link between cardiac sympathetic and vagal modulation and delta EEG demonstrated by the loss of cardiac autonomic activity fluctuations across shifts in sleep stages. Obstructive apneas and hypopneas alter the interaction between both signals differently.

Adult↗

PubMed2005

QRS artifact elimination on full night sleep EEG.

Spectral analysis is now a standard procedure for analyzing the electroencephalograms (EEG) obtained by polysomnographic recordings. These numerical methods assume an artifact-free EEG since artifacts create spurious spectral components. Our aim was the development of a QRS artifact removal technique that might be applied to full night EEG with a minimal human intervention. This technique should handle one EEG channel, with or without use of one ECG channel. Variance minimization, independent component analysis (ICA), morphological filters (MF) have been implemented. Careful attention has been given to define the MF structuring element. The tests on artifact-simulated and real data were checked on the residual ECG spectral components present in the cleaned EEG. The best results are obtained by the MF when the structuring element is an artifact template defined either directly on the EEG or on the ICA ECG component. Further developments are required to identify and subtract the T-wave artifacts.

Algorithms↗

PubMed2004

Progressive aging does not alter the interaction between autonomic cardiac activity and delta EEG power.

OBJECTIVE: We tested the hypothesis that the reductions of the changes in the respective influence of the cardiac sympathetic and vagal activity control and delta EEG activity with aging alter the interactions between the heart rate variability (HRV) and the delta sleep EEG power band. METHODS: A polysomnography was performed on 16 healthy young men and 19 healthy middle-aged men across the first 3 NREM-REM cycles. Spectral analysis was applied to electrocardiogram and electroencephalogram recordings. High Frequency (HF(nu)) of HRV as well as the maximum of cross-spectrum, coherency, gain and phase shifts between HF(nu) and delta sleep EEG power band were compared between both groups. RESULTS: Young men experienced more deep sleep than middle-aged men (P<0.001). In middle-aged subjects, HF(nu) was lower than the HF(nu) of their younger counterparts (P<0.001), but they showed similar increases during NREM sleep and similar decreases during REM sleep as the young subjects. Cross-spectrum values, coherency, gain and phase shifts between HF(nu) and delta were identical between the two groups. Modifications in HF(nu) show parallel changes and precede changes in delta EEG band by a similar leads of 11+/-6min in young men and 9+/-7 min in middle-aged men (P=0.23). CONCLUSIONS: Reduced changes in the respective influence of the cardiac sympathetic and vagal activity and delta EEG activity with progressive aging do not alter the relationship and phase difference between changes in the relative predominant cardiac vagal activity and delta power in middle-aged men. SIGNIFICANCE: Interaction between the cardiac sympathetic and vagal activity with delta EEG activity is maintained in middle-aged men.

Adolescent↗

PubMed2004

[Antidepressants: TCA versus SSRI versus other new agents].

The medications that appeared in the last two decades, offer praticians a wider choice than ever in the treatment of major depressive disorders. The aim of this article was first to compare tricyclic antidepressants and serotonine selective reuptake inhibitors. It was quite obvious that it was impossible to take no account of the birth of newer antidepressants. So we reviewed the efficacy--throughout their mechanims of action--of those different antidepressive agents, as well as their side-effects. One could think that the coming-out of molecules simpler to use, would facilitate the prescription. In fact, it does and it doesn't; it allows praticians, more than before, to accord with their clinical touch. That means that, at comparable efficacy, we now can choose therapeutic agents that fit more adequately a particular patient, his/her characteristics as well as his/her somatic and psychiatric history.

Antidepressive Agents, Tricyclic↗

PubMed2003

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.

Adolescent↗

PubMed2002

Correlations using the NREM-REM sleep cycle frequency support distinct regulation mechanisms for REM and NREM sleep.

Polysomnograms of most homeothermic species distinguish two states, rapid eye movement (REM) and non-REM (NREM) sleep. These alternate several times during the night for reasons and following rules that remain poorly understood. It is unknown whether each state has its own function and regulation or whether they represent two facets of the same process. The present study compared the mean REM/NREM sleep ratio and the mean number of NREM-REM sleep cycles across 3 consecutive nights. The rationale was that, if REM and NREM sleep are tightly associated, their ratio should be comparable whatever the cycle frequency in the night. Twenty-six healthy subjects of both sexes were recorded at their home for 4 consecutive nights. The correlation between the REM/NREM sleep ratio and the number of cycles was highly significant. Of the two sleep components, REM sleep was associated to the number of cycles, whereas NREM sleep was not. This suggests that the relationship between REM sleep and NREM sleep is rather weak within cycles, does not support the concept of NREM-REM sleep cycles as miniature units of the sleep process, and favors the concept of distinct mechanisms of regulation for the two components.

Adolescent↗

PubMed2002

[Chronic fatigue syndrome: psychiatric perspectives].

Chronic fatigue syndrome (CFS) is a common illness of unknown etiology and pathogenesis characterized by severe disabling fatigue and a variety of musculoskeletal, neurocognitive, mood symptoms and sleep disorders lasting at least six months. A significant proportion of patients fulfilling operative criteria for a diagnosis of CFS will also meet criteria for a psychiatric disorder such as depression, somatization or anxiety disorders. Premorbid lifestyle may play a predisposing, and/or perpetuating role in CFS. Some patients improve with time but most remain functionally impaired for several years. A variety of interventions have been used in the treatment and management of CFS. Interventions which have shown promising results include cognitive behavioural therapy and graded exercise therapy. Antidepressants can be useful particularly in the case of comorbid affective disorders. Development of good therapeutic doctor-patient alliance with empathic care is central to the effective management of CFS. In this article we overview the nature and definition of CFS. The prevalence, the prognosis and the psychopathological issues are presented. The management of this controversial syndrome is discussed.

Anxiety Disorders↗

PubMed2002

[Results of the third medical doctorate at the Brussels Free University: relationship with the first three years in the first generation students].

The aim of our study was to assess the relationships between the end-of-year results in the 1st session across 4 study years (the first 3 years and the 6th year) of medical school at the "Université libre de Bruxelles" in a group of 102 students, before initiation of the numerus clausus selection. In particular, we wanted to evaluate whether success in the 6th year was significantly related to the results in the preceding years, notwithstanding other non-academic factors, in two cohorts of students (1994-2000 and 1995-2001). Results showed that success in the 3rd doctorate was only slightly correlated to results in the first three years of study. The 3rd year final percentage was the only variable allowing to significantly predict a very good grade in the 6th year, but its actual contribution was very weak. On the other hand, based on their percentage, the ordering of students each year showed poor stability: three quarter of the students did either progress or regress in the 6th year compared to their rank in the first 3 years of study. These results are discussed with a special emphasis on the particular study sample, selected on the basis of a yearly success in 2 sessions maximum and in the context of the issue of students selection.

Belgium↗

PubMed2002

[The psychiatry department].

The Department of Psychiatry was first opened in April 1978. It is one of the largest sector of the hospital and contains 90 beds including a sleep laboratory and an adolescent unit. The clinical activities are broad and multidisciplinary, including novel psychopharmacological and psychotherapeutic and psychosocial approaches. Educational and research activities have also been developed, in particular in the areas of behavioral genetics, sleep physiology, brain imaging and psychosocial research and training.

Belgium↗

PubMed2001

Shorter REM latency associated with more sleep cycles of a shorter duration in healthy humans.

A significant association between rapid eye movement (REM) sleep latency and the number of non-REM/REM sleep cycles was found 15 years ago in a large retrospective study. The present prospective study further explored this intra-sleep relationship and analyzed the links between these two variables and the mean cycle duration. It was based on a carefully selected group of healthy control subjects whose sleep was polysomnographically recorded at home for 4 sequential nights. The latency of REM sleep was inversely correlated with the number of cycles and positively correlated with the mean cycle duration, both in individual nights and on means of 4 nights. The present study demonstrated that variations in the number of cycles or the mean cycle duration between the nights are far less important than the substantial differences observed between subjects. Present outcomes support the study of sleep cycle periods and frequencies in those psychiatric disorders where REM sleep latencies have been found to be shorter, and they suggest that these variables be included in sleep studies in which cycles are compared with each other.

Adolescent↗

PubMed2001

Effects of aging and cardiac denervation on heart rate variability during sleep.

BACKGROUND: Cardiac vagal predominance increases the RR interval and RR high-frequency (HF) variability during non-rapid eye movement (non-REM) sleep (stages I through IV) in young subjects. Aging suppresses deep sleep, but effects of age-related changes in sleep architecture on RR are unknown. Whether mechanical effects of changes in the breathing pattern on the sinus node during sleep affect RR variability is unclear. METHODS AND RESULTS: Polygraphic sleep recordings and RR and RR spectral profiles were determined in 8 young (22.5+/-3.3 years) and 8 older (55.0+/-7.3 years) healthy volunteers. HF oscillations in RR of 8 cardiac-denervated heart transplant recipients determined mechanical effects of respiration on the sinoatrial node during sleep. Transition from wakefulness to non-REM sleep increased the RR interval in young and older subjects and increased the HF variability of RR in the young (P:<0.05) but not in the older subjects. Older subjects disclosed a faster RR (P:<0.01) and a lower HF variability (P:<0.05) during non-REM sleep than the young subjects. Aging did not affect light and REM sleep but decreased deep sleep (stage IV) from 39+/-23 to 6+/-6 minutes (P:<0.001). Reduction in sleep stage IV with aging blunted the increase in RR and in RR HF variability during non-REM sleep (r>0.55, P:<0.05). Transition from wakefulness to non-REM sleep doubled the markedly reduced HF variability of RR in the heart transplant recipients (P:<0.05). CONCLUSIONS: Disappearance of deep sleep with aging impairs nocturnal increase in cardiac vagal activity. Mechanical effects of changes in breathing pattern during sleep favor increases in HF oscillations of the RR interval during non-REM sleep.

Adolescent↗

PubMed2000

Characteristics of spontaneous sleep with varying NREMS Episodes in healthy men: implication for delta activity homeostasis.

STUDY OBJECTIVES: We investigated the effects of the variation in the number of NREMS episodes on human sleep, in particular on delta activity distribution. PARTICIPANTS: Forty-one medication-free healthy men without personal or family history of psychiatric disorders. INTERVENTIONS: Subjects slept four consecutive nights, the last three were analyzed. Sleep was undisturbed and uninterrupted following self-selected schedule. RESULTS: With the exception of one night out of 123, subjects slept at least four NREMS episodes with 80% presenting five or six episodes per night. Yet, only 24% slept the same number of NREMS episodes across three nights. Shorter first NREMS episode was associated with greater number of NREMS episodes, and the total number of NREMS episodes was significantly predicted by the duration of the first one. Whether subjects slept four, five or six NREMS episodes, the proportion of TST spent in REMS, total delta power, total spectral power and the rate of delta power in the first NREMS episode did not differ between subjects. In each night, the distribution of delta activity across the first four NREMS episodes was not modified by the total number of NREMS episodes. CONCLUSION: When spontaneous sleep is allowed, healthy men mostly sleep beyond the fourth NREMS episode. Based on delta activity distribution across the first four episodes, we have demonstrated that the number of NREMS episodes does not modify delta sleep homeostasis. Only duration of first NREMS episode predicts the number of NREMS episodes slept. These results suggest that sleep homeostasis and NREMS-REMS alternation may be two independent processes.

Adult↗

PubMed2000

Compliance with nasal continuous positive airway pressure assessed with a pressure monitor: pattern of use and influence of sleep habits.

The aim of the study was to assess compliance with nasal continuous positive airway pressure (N-CPAP) at home in patients with obstructive sleep apnoea syndrome (OSAS) and to search for predictors of compliance. We studied a cohort of 106 consecutive patients (91 men, 15 women) with a median apnoea hypopnoea index of 62.4 (range 21-132) h(-1), equipped at home with a Rem+ Soft device (Sefam, France), including a pressure monitor and a real-time clock. During the third and fourth months of treatment, the patients used their machine a median of 88% of days (16-100%), with a mean effective use of 5.6 (1.3-11.2) h per effective day. Residual apnoea index on N-CPAP, as recorded by the monitor, was 1.5 (0.3-27.6) h(-1). Mean clock-time for starting with N-CPAP was 23 h 54 min (21 h 34-01 h 42). The mean effective use per effective day correlated negatively with the minimal (and the mean) level of oxyhaemoglobin saturation (r(s) = -0.24, P < 0.05) while the percentage of days the machine was used correlated negatively with the percentage of slow wave sleep (r(s) = -0.22, P < 0.05) at baseline polysomnography. In a subset of 30 subjects, earlier start on N-CPAP correlated with longer use of the device in 22 patients (median r--0.48). We conclude that a pressure monitor allows reporting on compliance in terms of regularity (% of days the machine is used) and length of sleep on N-CPAP (effective use per effective day). These compliance variables show modest correlations with baseline polysomnographic features. Late bedtime should be discouraged as it might decrease compliance.

Bias↗

PubMed2000

Depression and sleep disorders: clinical relevance, economic burden and pharmacological treatment.

A wide range of studies have been published over the past two decades that involve the intersection of sleep EEG, insomnia, psychiatric illness (especially depressive disorders) and psychopharmacology. Much of value has been discovered, but there have also been false starts and contradictory results. There is in fact strong evidence that insomnia is associated with medical and psychiatric illness and that the sleepiness associated with insomnia is the cause of many accidents. Thus, the direct (visits to doctors, cost of sleeping medication, complications from use of these medications) and indirect (accidents, quality of life) costs of insomnia are enormous and constitute a major public health problem in the industrialized countries. Believing that it is now timely to assess the state of this important research area, a consensus conference was convened on June 26-28, 1998, in Porto Cervo (Italy) to attempt to clarify the important issues and findings on the clinical effect of the different classes of antidepressant drugs on sleep quality in depression. The participants' consensus on some of the main topics is presented with the hope that this discussion and analysis will contribute to productive research in this important field.

Antidepressive Agents↗

PubMed2000

Mild to moderate sleep respiratory events: one negative night may not be enough.

STUDY OBJECTIVES: Reports on the reproducibility of apnea-hypopnea indexes (AHIs) across sequential polysomnography (PSG) sessions are conflicting, leading to a lack of clear recommendations on the optimal use of this technique: is one night of monitoring sufficient or is a second night required in order to safely reject the diagnosis? DESIGN: Retrospective comparison of two consecutive nights. SETTING: Sleep unit of a tertiary-care facility. PATIENTS: Two hundred forty-three subjects with suspected sleep apneas. INTERVENTIONS: Two sequential PSG sessions in a sleep unit. MEASUREMENTS AND RESULTS: Using analysis of covariance for repeated measures, with age and body mass index as covariates and gender as a cofactor, a classic first-night effect was found for sleep variables. In addition, a night effect was demonstrated for sleep respiratory variables. Moreover, the high variability of AHIs showed that many patients had their condition diagnosed on only one of the two nights, and more often on the second night than on the first. The gain in detection by adding a second night when the results of testing on the first were negative was between 15% and 25%, according to the AHI obtained on night 1. CONCLUSIONS: Considering the disability associated with sleep apnea/hypopnea syndrome, as well as its global cost for society, the present study shows that it is worth performing two consecutive PSG sessions or at least a second one when the result of the first one is negative in all patients admitted for apnea detection.

Body Mass Index↗

PubMed2000

[New neuroleptic drugs].

Novel antipsychotics are still frequently referred to as atypical. Following a brief review of the significant literature, they are presented under the sole perspective of their extrapyramidal side effect profile. Thereby, answers to whether they are novel or atypical are revisited. A tentative algorithm for their prescription is proposed as well.

Algorithms↗

PubMed1999

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.

Adolescent↗

PubMed1999

Genetic control of 24-hour growth hormone secretion in man: a twin study.

The aim of this study was to delineate the contributions of genetic and environmental factors in the regulation of the 24-h GH secretion. The 24-h profile of plasma GH was obtained at 15-min intervals in 10 pairs of monozygotic and 9 pairs of dizygotic normal male twins, aged 16-34 yr. Sleep was polygraphically monitored. Significant pulses of GH secretion were identified using a modification of the computer algorithm ULTRA. For each significant pulse, the amount of GH secreted was calculated by deconvolution. A procedure specially developed for twin studies was used to partition the variance of investigated parameters into genetic and environmental contributions. A major genetic effect was evidenced on GH secretion during wakefulness (with a heritability estimate of 0.74) and, to a lesser extent, on the 24-h GH secretion. Significant genetic influences were also identified for slow wave sleep and height. These data demonstrate that human GH secretion in young adulthood is markedly dependent on genetic factors.

Adolescent↗