The differences in sleep profile changes under continuous positive airway pressure (CPAP) therapy between non-obese, obese and severely obese sleep apnea patients.

Sleep disturbances in obstructive sleep apnea are caused mainly by repetitive apneas and hypopneas. An alternative factor contributing to disordered sleep may be the obesity, which is frequently associated with sleep apnea. The sleep disturbing effect of obesity was found previously in obese nonapneic subjects. The aim of this study was to evaluate the effect of obesity on sleep quality in sleep apnea patients in particular in patients under continuous positive airway pressure (CPAP) with successfully normalized respiration. We reviewed the archive data of 18 non-obese, 18 obese and 17 severely obese age and gender matched sleep apnea patients treated with CPAP. The polysomnographic parameters from the diagnostic night, from the second night under CPAP and from the follow up night (after three months of CPAP use) were compared. Before CPAP the apnea hypopnea index was worse in obese and in severely obese group and it normalised under CPAP in all groups. The severely obese group showed more light sleep and less REM sleep before CPAP and inversely - less light and more REM sleep in the second night under CPAP than the non-obese group. In the follow up, there was no differences in sleep profile between groups. This study indicates obesity does not affect the sleep independently of respiratory disorders. Before therapy it is associated with more severe sleep apnea and indirectly with worse sleep quality.

Dynamics of electroencephalogram entropy and pitfalls of scaling detection.

In recent studies a number of research groups have determined that human electroencephalograms (EEG) have scaling properties. In particular, a crossover between two regions with different scaling exponents has been reported. Herein we study the time evolution of diffusion entropy to elucidate the scaling of EEG time series. For a cohort of 20 awake healthy volunteers with closed eyes, we find that the diffusion entropy of EEG increments (obtained from EEG waveforms by differencing) exhibits three features: short-time growth, an alpha wave related oscillation whose amplitude gradually decays in time, and asymptotic saturation which is achieved after approximately 1 s. This analysis suggests a linear, stochastic Ornstein-Uhlenbeck Langevin equation with a quasiperiodic forcing (whose frequency and/or amplitude may vary in time) as the model for the underlying dynamics. This model captures the salient properties of EEG dynamics. In particular, both the experimental and simulated EEG time series exhibit short-time scaling which is broken by a strong periodic component, such as alpha waves. The saturation of EEG diffusion entropy precludes the existence of asymptotic scaling. We find that the crossover between two scaling regions seen in detrended fluctuation analysis (DFA) of EEG increments does not originate from the underlying dynamics but is merely an artifact of the algorithm. This artifact is rooted in the failure of the "trend plus signal" paradigm of DFA.

The influence of obesity on sleep quality in male sleep apnea patients before and during therapy.

Evidence exists that obesity, even in the absence of sleep related respiratory disorders, affects sleep negatively. In this study we examined the influence of obesity on sleep quality of male sleep apnea patients before and after breathing normalization with continuous positive airway pressure (CPAP). We compared the polysomnography from the diagnostic night, second night with CPAP, and a control night (three months later) in 13 non-obese, 13 obese, and 12 severely obese male obstructive sleep apnea patients. In the diagnostic polysomnography, obese and severely obese subjects showed increases in apnea-hypopnea index (AHI) and NREM-1 sleep, and decreases in min SaO(2), REM sleep, and partially slow wave sleep (SWS), when compared with the non-obese group. In the second night under CPAP, normalization of the AHI and a rebound of REM and SWS occurred, which was more pronounced in severely obese than in the non-obese and obese group. The polysomnography recorded three months thereafter revealed no differences in sleep stages between the groups. We conclude that after the long-term CPAP therapy, no effect of obesity on sleep quality is apparent.

Sleep disorderd breathing and recurrence of cerebrovascular events, case-fatality, and functional outcome in patients with ischemic stroke or transient ischemic attack.

Ninety one patients with stroke or transient ischemic attack (TIA) were screened for sleep-disordered breathing (SDB). Case fatality, rate of recurrence of cerebrovascular events, and functional outcome were analyzed during a 2-year follow-up. The patients were stratified into groups: without (AH < or =5) and with SDB (AHI >5). SDB was present in 61 (67.7%) patients with stroke or TIA. The rate of recurrence of TIA or stroke in patients with SDB was significantly higher (12 patients, OR=1.52, P<0.05) as compared with patients without SDB (3 patients) within two years of observation. Case-fatality rates were not significantly different (4 patients with SDB and 2 patients without SDB). Our data show that SDB significantly increases the incidence of recurrent cerebrovascular events in patients with TIA or stroke in a two-year follow-up. SDB in patient with stroke or TIA did not influence functional outcome of stroke during the long-term observation.

Sleep related breathing disorders in patients with ischemic stroke and transient ischemic attacks: respiratory and clinical correlations.

Fifty five patients with ischemic stroke and 15 patients with transient ischemic attacks (TIA) were screened for sleep related breathing disorders (SRBD). Apnea-hypopnea index (AHI) and desaturation index (DI) were analyzed. The clinical status was assessed with National Institute of Health Stroke Scale (NIHSS). The patients with stroke were stratified into groups: without (AHI10). SRBD were present in 36 patients with stroke and in 10 patients with TIA. There were significant differences in the clinical status on admission, as quantified with NIHSS, between stroke patients with mild and moderate or severe SRBD. AHI positively correlated with NIHSS on admission in stroke patients (r=0.54, P<0.01). The final NIHSS score was significantly greater in patients with moderate or severe SRBD than in those with mild SRBD: 3.4+/-1.9 and 1.8+/-1.2, respectively. Our data suggest that the severity of SRBD is related to the clinical status on admission and it influence the clinical outcome after ischemic stroke.

The influence of acute progressive hypoxia on bioelectrical activity of the brain.

Hypoxia, a noxious and hyperventilatory stimulus and a modifier of neuronal metabolism, could influence cortical function. In this study we attempted to assess any such influence, its determinants, and particularly the role in it of the accompanying hypoxic emotional distress. We addressed the issue by examining the associations among EEG, ventilation, and anxiety during progressive poikilocapnic hypoxia (end-point SaO(2) approximately 75%) in 12 awake healthy volunteers (mean age 27.5 +/-0.7 yr). All subjects hyperventilated in response to hypoxia and 3 of them had a high level of anticipatory anxiety that forced one person to discontinue the test. We failed to show any major effect of hypoxia on the EEG pattern analyzed by visual inspection or wavelet power spectra. Therefore, no relationship between the ventilatory and cortical activity responses to hypoxia could be established. Cortical activity changes appeared, however, in the subjects who experienced emotional distress during the test. These changes were apparent on an expanded analysis of the EEG signal by the use of the Lempel-Ziv complexity that takes into account the ordering of variations in the signal, rather than only the relative frequency of events analyzed by the Shannon entropy. The Lempel-Ziv complexity offers promise as a novel method for unraveling fine and otherwise unexpressed alterations in cortical bioelectrical activity.

The incidence of sleep apnea in patients with stroke or transient ischemic attack.

Disorders of breathing during sleep are defined as cessation or reduction of air flow thorough the upper airway, accompanied by a decrease of oxygen saturation. The results of many studies underline the association between sleep-disordered breathing (SDB) and cerebrovascular disorders. SDB, mostly obstructive sleep apnea syndrome (OSAS), is believed to be an independent risk factor of stroke and is related to poor outcome and increased long-term stroke mortality. The present study evaluated the frequency of SDB in patients with stroke or transient ischemic attack transient ischemic attack. We studied 43 patients (mean age 68.5 +/-11.0), which included 35 males and 8 females, with acute stroke (n=37) and transient ischemic attack (n=6). The assessment included body mass index (BMI), age, cardiovascular risk factors, and localization of stroke. All patients underwent all-night screening for SDB with a portable 8-channel recorder. The apnea/hypopnea index (AHI) for the whole group was 13.3 +/-15.2. AHI <5 was found in 16 patients. Overall, SDB was present in 27 (62.8%) patients with stroke and transient ischemic attack, stratified into those with AHI 5-10, (10 patients), 10-20 (8 patients), and AHI>20 (9 patients). In 15 patients, there was an increase in AHI >or=5 on assuming the supine position. The patients' mean BMI was 27.8 +/-4.7. The analysis of BMI, age, and localization of stroke was not sufficient to identify patients with high risk for SDB. We submit that overnight screening for SDB should be routinely performed in every patient after stroke and transient ischemic attack and it should become a diagnostic tool in neurological departments.

Wavelet mapping of sleep spindles in young patients with epilepsy.

Using the wavelet mapping of sleep spindles we investigated influence of focal epilepsy on spindle generation. We found that the maximum of sleep spindle intensity is usually localized away from the epileptic focus. We discuss the possibility of the application of wavelet mapping for localization of epileptic foci prior to epileptic neurosurgery.

The influence of age and gender on the latency of eye movement in healthy humans.

Standard measures of sleep recordings give differing results depending on the gender and they constantly change with age. Sleep latency increases, delta sleep decreases, and sleep tend to be shorter in duration and fragmented in middle-aged and elderly adults. The deterioration of sleep is observed earlier in men. In the 1980s, new measures called the Latency of Eye Movement (LEM) and the Mean Latency of Eye Movement (M-LEM) were proposed. Previous studies have shown that untreated patients with endogenous depression had the LEM and M-LEM shortened and that both indices get prolonged during treatment with antidepressants. On the other side, alcoholics in the abstinence period have LEM and M-LEM twice as long as healthy controls. In this study we set out to compare LEM and M-LEM in healthy humans according to the gender and age. The subjects of the study were 80 healthy volunteers: 40 males and 40 females, who were divided into 4 groups: females and males, below and above 40 years of age. In contrast to standard measures, our study did not reveal any significant changes of LEM or M-LEM due to the gender or age.

Cortical activity during hypoxic hyperventilation.

This study seeks to determine the pattern of electroencephalogram changes during stimulatory ventilatory responses to acute progressive hypoxia. Electroencephalograms were recorded in the 10-20 electrode system during progressive poikilocapnic hypoxic tests based on the rebreathing routine. Healthy subjects were used for he study. A major finding was that hypoxia decreased the power spectra of the alpha activity. The decrease was surprisingly rapid and greater at mild hypoxic desaturation when pulmonary ventilation was about to pick up than during the maximum hypoxic hyperventilation. The possible relation of hypoxic decline in brain bioactivity to the manifestation of hypoxic hyperventilation remains to be elucidated in further studies.

Comparison between eye movement latency and REM sleep parameters in major depression.

Alterations of sleep can be observed polysomnographically in approximately 90 percent of depressed patients. Most of the registered sleep abnormalities in depression also occur in other psychiatric disorders. Only some types of REM sleep alterations-- short REM latency, increase of REM density and shortening of mean latency of eye movements--were reported as more specific for affective disorders. In the present study polysomnograms of 21 medication free patients with major depressive disorder (assessed with a structured interview for DSM-III-R and Hamilton Scale) and 21 healthy controls were analysed. REM latency (LREM), REM density (RD), latencies of eye movements (LEM) and mean latency of eye movements (M-LEM) were calculated for both groups. Depressed patients (compared with healthy controls) showed increased RD (38.2% vs. 28.2%, p < 0.0001), shortened M-LEM (35.7 s vs. 48.3 s, p < 0.04) and shortening of LEM in the 1st (28.9 s vs. 48.9 s, p < 0.007) and 4th (27.0 s vs. 59.1 s, p < 0.043) REM sleep periods. LREM was not shortened significantly in depressives (78.5 min vs. 91.3 min, ns). In healthy subjects a negative correlation between M-LEM and RD was found (rho = -0.47, p < 0.03). Since in the current study depressed patients differed from healthy controls, especially concerning phasic activity during REM sleep, presented data support the essential role of REM density for the assessment of sleep in depression. As a quick and easy manner to compute measurement, M-LEM is suggested as additional parameter for the assessment of phasic activity during REM sleep.

Quantitative measure of complexity of EEG signal dynamics.

Since electroencephalographic (EEG) signal may be considered chaotic, Nonlinear Dynamics and Deterministic Chaos Theory may supply effective quantitative descriptors of EEG dynamics and of underlying chaos in the brain. We have used Karhunen-Loeve decomposition of the covariance matrix of the EEG signal to analyse EEG signals of 4 healthy subjects, under drug-free condition and under the influence of Diazepam. We found that what we call KL-complexity of the signal differs profoundly for the signals registered in different EEG channels, from about 5-8 for signals in frontal channels up to 40 and more in occipital ones. But no consistency in the influence of Diazepam administration on KL-complexity is observed. We also estimated the embedding dimension of the EEG signals of the same subjects, which turned to be between 7 and 11, so endorsing the presumption about existence of low-dimensional chaotic attractor. We are sure that nonlinear time series analysis can be used to investigate the dynamics underlying the generation of EEG signal. This approach does not seem practical yet, but deserves further study.

[Additional studies in the assessment of brain concussion]. / Badania dodatkowe w ocenie wstrzasnienia mózgu.

Following minor head traumas nervous system injuries develop at cellular level. In these cases only multidirectional analysis using various techniques can contribute to easier detection of focal lesions. The importance of neurophysiological methods, including electroencephalography (EEG), polysomnography, neuroimaging methods, such as cerebral tomography (CT), magnetic resonance (MRI), single photon emission computerised tomography (SPECT) and positron emission tomography (PET) in cases of minor head trauma. A brief review of the diagnostic methods applicable in the assessment of brain commotion shows that the dynamic development of new diagnostic techniques such as SPECT and MRI made possible a better insight into the processes taking place after minor trauma to the head. Together with traditional methods it can contribute to more objective demonstration of the symptoms, dynamics of the pathological process and more exact expertise of late sequelae of the trauma.

Inhibition of REM sleep by ipsapirone, a 5HT1A agonist, in normal volunteers.

In order to test the hypothesis that serotonergic mechanisms inhibit REM sleep via a 5HT1A receptor, we administered placebo and ipsapirone (10 and 20 mg by mouth 15 min before bedtime) to ten normal volunteers in a double blind fashion. Ipsapirone is a relatively selective 5HT1A receptor agonist. As predicted, ipsapirone prolonged REM latency and Mean Latency to Eye Movements (M-LEM), a measure of time between onset of REM sleep and the first eye movement of the REM period, and REM% at both doses compared with placebo. It also reduced sleep efficiency and total REM sleep time at the highest dose. These results support the hypothesis that systemic stimulation of 5HT1A receptors prolong REM latency and inhibit REM sleep.

[Norms of EEG sleep patterns for healthy Polish population aged from 60 to 79 years]. / Normy wzorca EEG snu dla zdrowej populacji polskiej w wieku 60-79 lat.

Norms of sleep EEG patterns for a healthy population aged from 60 to 79 years are presented. The collected data were compared with data found in the literature.

Norms of EEG sleep patterns for a healthy Polish population aged from 20 to 59 years.

Norms of sleep EEG patterns for a healthy population aged from 20 to 59 years are presented from which it was concluded that this age group forms a relatively stable pattern during the ontogenesis of sleep. The collected data were compared with data found in the literature.

[Norms of EEG sleep patterns for healthy Polish population aged from 20 to 59]. / Normy wzorca eeg snu dla zdrowej populacji polskiej w wieku 20-59 lat.

Norms of sleep EEG patterns for a healthy population aged from 20 to 59 years are presented from which it was concluded that this age group forms a relatively stable pattern during the ontogenesis of sleep. The collected data were compared with data found in the literature.

Latency of eye movement and other REM sleep parameters in bipolar depression.

Parameters of rapid eye movement (REM) sleep were measured in 10 endogenous bipolar depressive drug-free patients and in healthy subjects. A significant reduction of eye movement latency and larger standard deviations in the values for activity and density of eye movement were found in the depressed patients. The method applied in this study, embodying an aspect of cybernetic theory in pattern recognition, proved very useful for the elaboration of the biological data.