bluuebunny/crossref_metadata_2025 huggingface dataset:
Episodic hormone release in relation to REM sleep
Authors: BRANDENBERGER G.
Published: January 2009

SUMMARY  Similar periodicities of about 90–100 min characterize both hormone pulsatility and NREM‐REM sleep cycles suggesting that both processes could be temporally linked. From the current knowledge of the literature, it appears that, in spite of the diversity of the relationship between hormones and the sleep/wake cycle, systematic relationships exist between hormone pulses and the NREM‐REM sleep cycles. Early studies have demonstrated the temporal association between GH and SWS episodes occurring soon after sleep onset. Renin, a key enzyme of the renin‐angiotensin system, displays nocturnal oscillations that are associated strongly with the NREM‐REM sleep cycles, and represents the first identified biological marker of sleep stage alternation. SWS invariably occurs in the descending phases of TSH and cortisol pulses which suggests that some specific mechanisms of this sleep stage could modulate their levels or, conversely, that increased TSH and cortisol secretion prevents the occurrence of deep sleep. Apart from the period of sleep onset associated with reduced prolactin secretion, no systematic relationship has been found between REM sleep and hormone release. These results highlight the complexity of hormone and sleep interactions and provide a basis for further research into their functional significance.
Dreaming and REM sleep
Authors: FOULKES DAVID
Published: January 2009

SUMMARY  The discovery, 40 years ago, of REM sleep and of its putative association with dreaming in the adult human raised the possibility that neuroscientific investigations of REM‐sleep physiology would someday ‘explain’ the distinctive features of dream experience. I argue here against the possibility, since replicated psychological data demonstrate that REM sleep is neither a necessary nor a sufficient condition for dreaming to occur. Dreaming depends, rather, upon the possession of conscious representational intelligence in conjunction with any psychophysiological state in which ideation is being driven neither volitionally nor by external stimulation.
Slow‐wave sleep deprivation and waking function
Authors: WALSH JAMES K. , HARTMAN PAUL G. , SCHWEITZER PAULA K.
Published: January 2009

SUMMARY  Slow‐wave sleep (SWS) has been theorized to be an intense form of nonREM sleep, but selective deprivation of SWS or Stage 4 sleep has not been shown to cause greater decrements in alertness or performance, compared to deprivation or disruption of the other stages of sleep. The present experiment examined the effects of marked SWS deprivation (SD) for two nights, a control sleep disruption (CD) condition in which minutes of SWS were preserved, and a no sleep disruption (ND) condition. Daytime sleepiness was assessed with the multiple sleep latency test (MSLT) and performance was evaluated with the simulated assembly line task (SALT), neither of which was used in previous studies of SWS or Stage 4 sleep deprivation. In agreement with prior studies, two nights of SD did not cause greater daytime sleepiness than did CD, although sleepiness in both conditions was increased compared to the ND condition. In addition, neither SD nor CD caused declines in performance or mood. However, post hoc analysis suggests an interaction between SWS and sleep duration, such that sufficient SWS may tend to prevent adverse effects of mild sleep loss on waking function.
Renin as a biological marker of the NREM‐REM sleep cycle: effect of REM sleep suppression
Authors: BRANDENBERGER G. , CHARIFI C. , MUZET A. , SAINI J. , SIMON C. , FOLLENIUS M.
Published: January 2009

SUMMARY  We have previously described that, in normal man, the nocturnal oscillations of plasma renin activity (PRA) exactly reflect the rapid eye movement (REM)–non(N)REM sleep cycles, with increasing PRA levels during NREM sleep and decreasing levels during REM sleep. This study was carried out to determine whether REM sleep suppression affects nocturnal renin profiles and to define which sleep stage is essential for renin release.

In a first experimental series, REM sleep was suppressed by using clomipramine, a tricyclic antidepressant. Seven healthy young men were studied once during a night when a placebo was given and once during a night following a single dose of 50 mg clomipramine. Blood was collected every 10 min from 23.00 hours to 07.00 hours. PRA was measured by radio‐immunoassay and the nocturnal profiles were analysed using the pulse detection program ULTRA. Clomipramine suppressed REM sleep in all subjects but one, but did not affect the number of SWS episodes nor their duration. Similar PRA profiles were observed in both experimental conditions. Neither the mean levels, nor the number and the amplitude of the oscillations were modified and the normal relationship between slow wave sleep and increasing PRA levels was preserved.

In a second experimental series, REM sleep was prevented by rapidly awakening the subjects as soon as they fell into REM sleep. The four subjects studied attempted several times to go into REM sleep, but only when PRA levels were decreasing. The interruption of REM sleep by short waking periods did not disturb PRA for which the oscillations remained unaffected. Again, the relationship between SWS and increasing PRA levels was preserved.

These results provide evidence that mechanisms increasing slow‐wave activity are principally involved in increasing PRA levels and that replacing REM sleep by waking periods and light sleep does not modify nocturnal PRA oscillations.
Sleep apnoea in the Prader‐Willi syndrome
Authors: CLIFT S. , DAHLITZ M. , PARKES J. D.
Published: January 2009

SUMMARY  Seventeen children and young adults with the Prader‐Willi syndrome were investigated. Twelve of 17 subjects had excessive daytime sleepiness as determined by their own or parental report, a high Epworth Sleepiness Scale score or a short mean sleep latency. Night sleep disturbances were reported in seven subjects with snoring, mouth‐breathing, breath‐holding and occasional nocturnal enuresis. Polysomnography showed abnormalities of sleep structure with rapid eye movements without reduction in muscle tone at sleep onset in 12 subjects, and a high respiratory event index with frequent brief apnoeas, particularly in REM sleep, in 16 subjects. Most apnoeas were not accompanied by arousals. Seven subjects, all of whom were obese, were considered to have symptomatic sleep apnoea and were treated with continuous positive airway pressure (CPAP) but this was poorly tolerated in two. Five subjects continued CPAP over a 6‐month period resulting in subjective improvement in excessive daytime sleepiness in 3.

Excessive daytime sleepiness occurs in approximately two‐thirds of subjects with the Prader‐Willi syndrome. It is mainly of central origin but obstructive sleep apnoea may increase sleepiness, particularly in obese subjects.
Subjective sleepiness and physiological sleep tendency in healthy young morning and evening subjects
Authors: VOLK STEPHAN , DYROFF JÜRGEN , GEORGI KLAUS , PFLUG BURKHARD
Published: January 2009

SUMMARY  The Multiple Sleep Latency Test (MSLT) was performed twice after 8h and after 4h of night sleep in 15 healthy young subjects (mean age: 23 y). Seven subjects could be regarded as morning, 8 subjects as evening types. After 8h of sleep significantly more evening types napped at 08.00 hours and at 12.00 hours. Evening types rated themselves more sleepy on an hourly administered visual analogous scale (VAS). Sleep onset latencies (SOL) decreased, and the amount of Stages 1 and 2 increased in all subjects dependent on the sleep restriction condition. No significant differences between morningness and eveningness concerning SOL and structure of nap structure could be observed. After 4 h of sleep there was a marked increase in subjectively rated sleepiness during the morning hours in both groups.
Effect of unilateral somatosensory stimulation prior to sleep on the sleep EEG in humans
Authors: KATTLER HERBERT , DIJK DERK‐JAN , BORBÉLY ALEXANDER A.
Published: January 2009

SUMMARY  The hypothesis that local activation of brain regions during wakefulness affects the EEG recorded from these regions during sleep was tested by applying vibratory stimuli to one hand prior to sleep. Eight subjects slept in the laboratory for five consecutive nights. During a 6‐h period prior to night 3, either the left or the right hand was vibrated intermittently (20 min on‐8 min off), while prior to night 5 the same treatment was applied to the contralateral hand. The sleep EEG was recorded from frontal, central, parietal and occipital derivations and subjected to spectral analysis. The interhemispheric asymmetry index (IAI) was calculated for spectral power in nonREM sleep in the frequency range 0.25‐25.0 Hz for 0.5‐Hz or 1‐Hz bins. In the first hour of sleep following right‐hand stimulation, the IAI of the central derivation was increased relative to baseline, which corresponds to a shift of power towards the left hemisphere. This effect was most prominent in the delta range, was limited to the first hour of sleep and was restricted to the central derivation situated over the somatosensory cortex. No significant changes were observed following left‐hand stimulation. Although the effect was small, it is consistent with the hypothesis that the activation of specific neuronal populations during wakefulness may have repercussions on their electrical activity pattern during subsequent sleep.
Plasma insulin and lipid levels in untreated obstructive sleep apnoea and snoring; their comparison with matched controls and response to treatment
Authors: DAVIES R. J. O. , TURNER R. , CROSBY J. , STRADLING J. R.
Published: January 2009

SUMMARY  Obstructive sleep apnoea (OSA), and snoring are associated with coronary heart disease. To assess whether OSA or snoring may contribute to this by raising fasting lipid or insulin levels, venous fasting total cholesterol, triglyceride, very‐low‐density lipoprotein, low‐density lipoprotein, high‐density lipoprotein, and insulin were measured in 15 untreated OSA patients and 18 snorers. Each of these subjects was individually matched to a control of the same sex, age ± 10%, body index ± 15%, smoking and drinking habits. This produced study groups which did not differ significantly by any of these criteria. Fasting venous blood samples were collected at 06.30 hours following polysomnography, and analysed blind of the subjects respiratory status. The OSA patients were then treated with nasal continuous positive airway pressure. In 10 of these subjects lipid and insulin levels were repeated after more than three months treatment. Lipid and insulin levels were also remeasured in the controls matched to these 10 subjects. The end points were compared with paired t‐tests.

There was no difference in any of the end points when the untreated OSA patients and the snorers were compared to their matched controls (P>0.25 for all comparisons), and none of the indices changed when OSA was corrected with nasal continuous positive airway pressure (P > 0.25 for all comparisons).

Patients with obstructive sleep apnoea or snoring do not have significant fasting hyperlipidaemia or hyperinsulinaemia when compared to carefully matched controls. These factors are therefore unlikely to be the cause of the excess cardiovascular mortality experienced by this patient group.
Wavelets—a new tool in sleep biosignal analysis
Authors: JOBERT MARC , TISMER CHRISTIAN , POISEAU ERIC , SCHULZ HARTMUT
Published: January 2009

SUMMARY  The wavelet transform is a relatively new approach to data processing which has been applied in different areas such as signal, speech and image processing. In the last decade, many papers have been published on wavelet theory and its applications. The wavelet transform provides an elegant alternative to the classical Fourier or Gabor transforms unifying numerous signal processing techniques in a common framework. The purpose of the present paper is to provide an overview of the applicability of the wavelet transform to EEG signal analysis. In the first part of the paper the mathematical background is summarized. In the second part, applications to the sleep EEG field are presented and discussed. The results of these illustrations demonstrate the usefulness of the wavelet transform to solve various problems including signal parametrization, pattern recognition and biosignal representation.
Predictive value of specific risk factors, symptoms and signs, in diagnosing obstructive sleep apnoea and its severity
Authors: PILLAR GIORA , PELED NIR , KATZ NERI , LAVIE PERETZ
Published: January 2009

SUMMARY  A positive diagnosis of obstructive sleep apnoea (OSA) is based on a combination of characteristic symptoms and polysomnographic findings. The present study evaluated the specificity and sensitivity of several risk factors, signs and symptoms in predicting an Apnoea Index in 86 patients referred to the sleep laboratory with suspected OSA. All 86 subjects completed a detailed questionnaire, were interviewed, underwent a brief physical examination, and then a whole‐night polysomnographic study. Stepwise multiple regression analysis revealed that self reporting on apnoeas, neck circumference index (NCI), age, and a tendency to fall asleep unintentionally, were all significant positive predictors of apnoea index (AI), explaining 41.8% of the variability. The sensitivity of the model for predicting OSA (taking OSA as AI>10) was 92.2%, specificity was 18.2% and the positive predictive value was 76.6%. Raising the cut‐off AI values resulted in decreased sensitivity and increased specificity. Applying the predicting equation of AI to another group of 50 patients referred to the sleep laboratory with suspected OSA revealed similar results. However, running the equation on 105 offspring of OSA patients who did not complain of OSA‐associated symptoms resulted in 32% sensitivity and 94% specificity in predicting OSA. It is concluded that questionnaires, interviews and physical examination, can only vaguely predict AI, and cannot replace polysomnographic recordings. However, the low rates of false negative in predicting AI > 10, and the low rates of false positive in predicting AI > 50, can be used for specific purposes.
Effects of a cognitive‐behavioural weight loss programme on overweight obstructive sleep apnoea patients
Authors: KAJASTE S. , TELAKIVI T. , MUSTAJOKI P. , PIHL S. , PARTINEN M.
Published: January 2009

SUMMARY  Thirty‐two obese patients (Body Mass Index (BMI) = 38.5 ± 3.7) with obstructive sleep apnoea (the average number of oxygen desaturations per hour of sleep exceeding 4% from the baseline (OD14) = 38.6 ± 23.9) underwent a one‐year cognitive‐behavioural weight reduction programme with a one year follow‐up period.

The criteria for successful treatment were (i) a decrease in OD14 to less than 10 and (ii) a decrease in OD14 that was greater than 50%. Fourteen (44%) patients were considered to be treated successfully at six months. When the patients were grouped according to weight loss 23 patients had lost more than 5 kg; 12 (52%) of them belonged to the group treated successfully. At 24 months, however, only three (9%) patients could be regarded as treated successfully and six patients had been transferred to other treatment modes (Nasal Continuous Positive Airway Pressure (nCPAP) and uvulopalatopharyngoplasty (UPPP)). The changes in weight correlated with the changes in OD14 (r = 0.47 and 0.63 at the 6‐month and the 24‐month evaluation, respectively).
Sleep, Dreams and memory: an overview
Authors: CIPOLLI CARLO
Published: January 2009

SUMMARY  Investigations into the role played by sleep in information processing have consistently shown that the retention of information is better when the memory storage is followed by a period of sleep than of waking. Less definitive evidence, however, is available as to whether the better performance is mainly due to (a) reduction of interference during sleep, (b) slowing down of decay, or (c) consolidation processes at work during sleep. Important insights as to whether consolidation takes place during sleep have recently been provided by the thematic continuity of dreams elaborated in the same night and by the repeated incorporation of pre‐sleep stimuli into dream contents. The analysis of such aspects of dreaming indicates that the items of information which are repeatedly accessed during sleep and elaborated for insertion into the ongoing dream experience are better retained at delayed recall. Finally, it is suggested that the use of the strategies applied in studying the information processing in normals may also be extended to sleep‐disturbed individuals, in order to establish how memory functioning during sleep is influenced by sleep disturbances.
The disturbance of cognitive processes in narcolepsy
Authors: SCHULZ HARTMUT , WILDE‐FRENZ JOHANNA
Published: January 2009

SUMMARY  Neuropsychological methods have been applied by different authors to investigate cognitive processes such as attention, information processing, memory and psychomotor performance in narcoleptic patients. A review of the results strongly suggests that cognitive processes in narcoleptic patients are not impaired on a functional but only on a temporal level. Providing that short and challenging tasks were used, the performance of narcoleptic patient did not differ significantly from that of healthy subjects. Performance was impaired mainly when a low and monotonous information input had to be processed, a situation which is typical for tests of vigilance. This was supported by this study measuring critical flicker fusion (CFF) at 15‐min intervals for 10 hours in 10 narcoleptic patients and matched healthy controls. While peak performance did not differ between groups, narcoleptic patients were unable to perform at a steady level through the day. Tiredness and episodes of sleepiness seem to be the main reason for cognitive impairments in narcolepsy.
Magnetic stimulation of the human brain during phasic and tonic REM sleep: recordings from distal and proximal muscles
Authors: Stalder S. , Rösler K. M. , Nirkko A. C. , Hess C. W.
Published: January 2009

During REM sleep, a powerful postsynaptic inhibition of spinal motoneurons induces a generalized muscle hypotonia. Despite this inhibition, it has been shown that by transcranial magnetic stimulation of the brain (TMS), muscle responses of normal amplitude can be evoked in small hand muscles of humans. Tonic innervation during sleep is different in postural vs. limb muscles, and the spinal inhibition differs during tonic vs. phasic REM episodes, Both phenomena may affect muscle responses to TMS. In this study, muscle responses of 14 healthy subjects were compared to TMS in abductor digiti minimi, lumbar erector spinae, trapezius, and diaphragm during phasic and tonic REM sleep. In all four muscles, the amplitudes of the muscle responses were extremely variable, ranging for example in trapezius from −100% to +473% as compared to wakefulness. There was no systematic difference between the muscles. Moreover, no differences were found for TMS during phasic REM events compared to tonic REM sleep. Thus, responses to TMS during REM sleep may be preserved, with a decreased or increased amplitude. As a likely explanation, the cortical excitability and/or the spinal inhibition fluctuates during REM sleep in humans.
Consolidated and distributed nap schedules and performance
Authors: Bonnet M. H. , Arand D. L.
Published: January 2009

This study compared alertness and psychomotor performance over an extended work period in which participants received either a 4‐h afternoon nap or four 1‐h naps during the night. It was hypothesized that alertness and performance would be superior during the night following the 4‐h afternoon nap and that the overall level of performance would be related to the amount of sleep obtained. It was found that when a series of 1‐h naps was taken during the normal night period, oral temperature and psychomotor performance also declined. However, performance was relatively improved on the following evening. In contrast, with an effective 4‐h prophylactic nap, performance remained near baseline levels across the night. It was concluded that the placement of sleep periods during extended work be based on knowledge of when maximal performance would be required.
Treatment in the narcoleptic syndrome: self assessment of the action of dexamphetamine and clomipramine
Authors: Chen S. Y. , Clift S. J. , Dahlitz M. J. , Dunn G. , Parkes J. D.
Published: January 2009

Subjective evaluation of the effect of treatment of excessive daytime sleepiness (EDS) with dexamphetamine and of cataplexy with clomipramine was made in 124 subjects with the narcoleptic syndrome. Drug effects were evaluated by self‐report of the propensity to EDS and cataplexy as determined by the Epworth Sleepiness Scale and a rating scale of anticipation‐associated loss of postural motor tone during long‐term therapy. The effects of dexamphetamine alone (60 subjects), clomipramine alone (16 subjects) and combined dexamphetamine‐clomipramine treatment (48 subjects) were evaluated.

Self‐reports indicated that the propensity to EDS was reduced by approximately 20% by dexamphetamine (mean dosage 16 mg/24 h, range 5–60: mean treatment period 21 years, range 2–45). The propensity to cataplexy was reduced by 23% by clomipramine (mean dosage 64 mg/24 h, range 25–125: mean treatment period 14 years, range 1–24). Dexamphetamine alone, in addition to reducing the propensity to EDS also reduced the propensity to cataplexy. Clomipramine alone reduced cataplexy, but not EDS. Combined dexamphetamine‐clomipramine treatment caused a reduction in the propensity to EDS and cataplexy of similar magnitude to that caused by dexamphetamine alone. Less than 10% of all subjects with the narcoleptic syndrome reported a daytime sleep propensity in the normal range whilst on dexamphetamine and no subject on clomipramine reported complete control of cataplexy. Long‐term treatment with dexamphetamine was associated with weight increase more commonly than weight loss. Weight gain was reported by two‐thirds of subjects taking clomipramine alone. Reports of weight loss were as common as reports of weight gain by subjects on combined dexamphetamine‐clomipramine treatment. Constipation, dry mouth and impaired sexual function were reported by 25%, 38% and 19% (respectively) of subjects on clomipramine.

This retrospective long‐term self‐report study investigated the propensity to, rather than the frequency of, episodes of EDS and cataplexy in subjects with the narcoleptic syndrome. This study suggests that long‐term drug treatment in the narcoleptic syndrome results in only minor reduction in attack propensity, in contrast to the findings of many previous short term objective studies, which suggest 50–80% reduction in attack frequency. Major factors limiting response to dexamphetamine in the narcoleptic syndrome include physician prescription of sub‐optimal drug dosages, and a low index between the limited therapeutic efficacy and frequent side‐effects of this drug.
Multi‐centre comparison of five eye movement detection algorithms
Authors: Värri Alpo , Kemp Bob , Rosa Agostinho C. , Nielsen Kim D. , Gade John , Penzel Thomas , Hasan Joel , Hirvonen Kari , Häkkinen Veikko , Kamphuisen H. A. C. , Mourtazaev M. S.
Published: January 2009

Although various investigators have suggested algorithms for the automatic detection of eye movements during sleep, objective comparisons of the proposed methods have previously been difficult due to different recording arrangements of different investigators. In this study the results of five eye movement detection algorithms applied to the same data were compared to visually scored data. The percentages of true and false detections are given for various threshold levels in rapid and slow eye movement detections. The methods gave best results when they were used with the same electrode montage they were designed for but the performance decreased when other montages were used. Subtracting the cross‐talk of EEG delta activity improved the correctness of eye movement detections.
Respiration in NREM and REM sleep after upper airway surgery for obstructive sleep apnoea
Authors: MARRONE ORESTE , SALVAGGIO ADRIANA , INSALACO GIUSEPPE , BONSIGNORE MARIA ROSARIA , CIMINO MARIA , GALLINA SALVATORE , SPECIALE RICCARDO
Published: January 2009

SUMMARY  To verify whether upper airway surgery in obstructive sleep apnoea syndrome affects differently respiration in NREM and REM sleep, 22 patients were studied by polysomnography before and three months after surgical treatment. On the average, treatment improved respiration during both sleep states, but no significant interaction was found between sleep state and effect of surgical treatment. According to the response to treatment, three groups of patients were identified: the first group (N= 6), with an improvement in apnoea‐hypopnoea index (AHI), percentage of sleep time spent in apnoea and hypopnoea (time in AH) and mean oxyhaemoglobin saturation (SaO2) in both NREM and REM sleep; the second group (N= 5), with an improvement in AHI only in NREM sleep, associated with improvement in mean SaO2 in both sleep states; the third group (N= 11), without any improvement in AHI and time in AH, either associated (N= 5) or not (N= 6) with an improvement in mean SaO2 in both sleep states. An increase in the percentage of hypopnoeas out of the total AHI after treatment could partly account for the apparent discrepancy between AHI and mean SaO2 behaviour in the subjects of the second group, but not in the patients of the third group who improved their mean SaO2. Mixed apnoeas occurred before surgery in six subjects; they remained numerous after surgery only in two subjects who did not show any SaO2 improvement. In conclusion, the degree of improvement in respiration after upper airway surgery was similar in every patient in NREM and REM sleep.
Firing of inferior colliculus neurons in response to low‐frequency sound stimulation during sleep and waking
Authors: MORALES‐COBAS GABRIELA , FERREIRA MARÍA INÉS , VELLUTI RICARDO A.
Published: January 2009

SUMMARY  In vivo extracellular recordings of 102 units in the central nucleus of the inferior colliculus (IC), were made in chronically implanted guinea‐pigs during the sleep/wake cycle. During wakefulness, the units were classified according to their response characteristics. Most neurons (63%) recorded showed changes, increasing or decreasing in the number of evoked discharges during the animal's transitions between wakefulness and slow‐wave sleep. In the paradoxical sleep phase, the result was similar; changes were observed in most neurons, while only 11% of units did not shift their discharge pattern during ipsilateral sound stimulation.

The post‐stimulus time histogram of the overall evoked pattern of discharge showed sleep/wake dependency, i.e. changed in 35% of the units recorded during the 50 ms of sound stimulation.

Fifty‐five percent of auditory neurons did not show any change in the spontaneous firing rate during slow‐wave sleep as compared to the previous waking period, while 22% exhibited a discharge increase and 23% decreased their firing. During paradoxical sleep, 14 out of 17 cells increased their spontaneous firing rate. The IC auditory neurons send descending connections to regions such as the dorsal pontine nuclei, known to mediate sleep processes. Thus, for constant auditory input, the firing rate or number of discharge variations are due to functional shifts in the sleeping brain. Auditory processing is present during sleep and differs from that observed during wakefulness. Differences were observed in the evoked firing number and/or spontaneous rate, as well as in the pattern of discharge. The ultimate reason for auditory unit shifts during sleep remains yet unexplained.
Cardiorespiratory control: an Integrated view H.‐P. Koepchen in memoriam
Authors: SCHLÄFKE MARIANNE E.
Published: January 2009

SUMMARY  H.‐P. Koepchen's presence at this symposium on cardiocirculatory function during sleep would have given us an inspiring impetus. His death has meant a severe loss for all of us. Koepchen's integrated view on cardiorespiratory control and rhythmicity has been the content of his late work. His considerations as documented in various papers are used for this contribution. They are based on earlier experimental studies of spontaneous coordinations of rhythmic activities in anaesthetized dogs, conscious men, and microelectrode recordings and local cooling experiments in the brain stem of anaesthetized dogs and cats, which he had worked on together with his students.
Blood pressure variability over 24 hours: its different components and its relationship to the arterial baroreflex
Authors: PARATI GIANFRANCO , DI RIENZO MARCO , OMBONP STEFANO , ULIAN LUISA , MANCIA GIUSEPPE
Published: January 2009

SUMMARY  This paper describes several different methods for the analysis of blood pressure and heart rate variability over the 24 hours, both in the time and in the frequency domain. The mechanisms possibly involved in the genesis of the variations in blood pressure and heart rate which occur over a 24‐hour period are also discussed. Finally, new approaches to the dynamic evaluation of the sensitivity of baroreflex control of heart rate and of its changes over the 24 hours in daily life conditions, based on computer analysis of the interaction between fluctuations in blood pressure and heart rate, are described. Data obtained by applying these methods in different clinical conditions (normotensive vs. hypertensive subjects, young vs. elderly individuals and pure autonomic failure patients) are presented.
Non‐invasive measurement of haemodynamics during sleep apnoea
Authors: ESCOURROU P. , TESSIER O. , BUREAU A. , NEDELCOUX H. , BOURGIN P.
Published: January 2009

SUMMARY  Sleep apnoeas are accompanied by large variations in heart rate (HR) and blood pressure (BP). This nocturnal variability in BP may be involved in the increased cardiovascular morbidity of these patients. Due to the complex interaction between asphyxia, intrathoracic pressure, cardiac function and autonomic activation, the exact haemodynamic mechanisms are unclear.

To evaluate the components of the BP surges at resumption of breathing (RB) a non‐invasive beat‐to‐beat measurement was taken of cardiac output (CO) by the pulse contour analysis of the Finapres signal. Six male normotensive patients, free of medication (37–60 y, BMI 26.5–43.0 kg m‐2) were studied during polysomnography (apnoea index: 22–69 h‐1). Systolic blood pressure rose from 126.5 ± 1.3 mmHg at beginning apnoea (P1) to 140.4 ±1.3 at RB (P<0.01, ANOVA). During sleep Stages 2 and 3, stroke volume decreased during RB to 96% of P1 value (NS). Due to an opposite change in HR, CO tended to rise at RB to 106% of P1. Computed total peripheral resistance rose during RB to 105% of P1 value (P <0.01).

Therefore, it is concluded that the surge in BP at RB after apnoea is due to concomitant increases in CO and in TPR. Both rises are presumably a consequence of sympathetic nervous activation by the arterial chemoreceptors.
Determinants of circadian blood pressure rhythm and blood pressure variability in obstructive sleep apnoea
Authors: NABE B. , LIES A. , PANKOW W. , KOHL F. V. , LOHMANN F. W.
Published: January 2009

SUMMARY  The prevalence of hypertension in patients with obstructive sleep apnoea (OSA) is high and blood pressure profile is characterized by nocturnal blood pressure (BP) elevation and increased nocturnal BP variability. Ambulatory 24‐hour‐biood pressure monitoring (ABPM) is a valid, non‐invasive method to describe circadian BP variation. Circadian BP profile and nocturnal BP variability were related to OSA severity (apnoea‐hypopnoea index, mean low O2), age and body mass index (BMI) in 73 patients with OSA. Prevalence of hypertension was 75%, and in 59% BMI was greater than 30 kg m‐2. A nocturnal decline of at least 10% from daytime mean BP values (night/day BP ratio <0.9; dipper) was found in only 25% of hypertensive patients and 39% of normotensive patients. Comparison between dippers and non‐dippers showed significant differences in apnoea severity (apnoea‐hypopnoea index 32 + 19 vs. 50 + 23/h, P<0.01; mean low O2 84.5 + 4 vs. 80.2 + 5.8%, P< 0.01) but not for age and BMI. In multiple regression analyses with age, body mass index, apnoea‐hypopnoea index and mean low O2 as independent and BP ratios and BP variability as dependent variables, sleep apnoea severity was the only independent predictor for circadian BP rhythm and nocturnal BP variability. The results presented here suggest that independent of age and obesity the severity of sleep apnoea is an important determinant of circadian BP variation and nocturnal BP variability.
Intrathoracic pressure changes and cardiovascular effects induced by nCPAP and nBiPAP in sleep apnoea patients
Authors: BECKER HEINRICH , GROTE LUDGER , PLOCH THOMAS , SCHNEIDER HARTMUT , STAMMNITZ AXEL , PETER JÖRG HERMANN , PODSZUS THOMAS
Published: January 2009

SUMMARY  The effect of nasal continuous positive airway pressure (nCPAP) and nasal bi‐level positive airway pressure (nBiPAP) on intrathoracic pressure and haemodynamics during wakefulness was studied in a group of nine patients with severe sleep apnoea. No patient took cardiovascular medication.

Patients were studied with a Swan Ganz catheter, an arterial line and an oesophageal balloon. nCPAP and nBiPAP were applied in the following pressure sequence: 5, 10 and 15 cm H2O of CPAP and 10/5 and 15/10 cm H2O of nBiPAP. Measurements were made at the end of a 5‐min period at each pressure level. Intrathoracic pressure was noted to increase to a level of approximately 50% of the pressure delivered at the mask. At a CPAP of 10 cm H2O and above, as well as at BiPAP of 10/5 or higher, there was a decrease in cardiac output (CO) and cardiac index (CI). CI fell below the normal value in two of the patients. Transmural pulmonary artery pressure (PPAtm) decreased at a CPAP of 15 cm H2O and at both BiPAP levels. Transmural right atrial pressure (PRAtm) decreased at both BiPAP levels. There were no differences in CO, CI, PPAtm and PRAtm between nCPAP and nBiPAP at equal inspiratory pressures. SaO2 increased during BiPAP 15/10 cm H2O, whereas heart rate and arterial blood pressure did not change significantly. The data presented here are consistent with the literature on positive end‐expiratory pressure (PEEP) applied via intratracheal tube and are likely to be due to a reduced venous return. It is concluded that nasally applied positive pressure may have acute negative effects on cardiac function in patients with sleep apnoea.
Ischaemic stroke, snoring and obstructive sleep apnoea
Authors: PARTINEN MARKKU
Published: January 2009

SUMMARY  Ischaemic stroke occurs most often during the morning hours before noon. In recent studies the peak time of onset has been between 10.00 and 12.00 hours. Snoring every night or almost every night (habitual snoring) is in relation with ischaemic stroke. Snoring occasionally, on the contrary, is not significantly related with stroke. Habitual snoring is the most typical sign of obstructive sleep apnoea syndrome and it is strongly associated with being overweight. Other possible pathophysiological factors that are in relation with habitual snoring, obstructive sleep apnoea and stroke include arterial hypertension, changes in fibrinolytic activity, adult onset diabetes and smoking. It remains to be seen whether nightly occurring partial upper airway obstruction (habitual snoring) with intrathoracic pressure changes is an independent risk factor of ischaemic stroke. There is recent evidence that everything cannot be explained by other known risk factors.
Daytime waking autonomic function and vascular control in OSA
Authors: HEDNER JAN
Published: January 2009

SUMMARY  This paper deals with the potential role of two blood pressure regulatory systems in the development of hypertension in obstructive sleep apnoea (OSA). Beside the acute and long‐term sympathoexcitation documented in this disease, there seems to be an impaired endothelium‐dependent vascular relaxation. In particular, nitric oxide (NO)‐mediated vasodilatation was impaired in patients with OSA. Both these changes act to increase blood pressure during physiological conditions. However, they may not be determinants for hypertension development in OSA as no differences between normo‐ and hypertensive patients with OSA were detected. Nevertheless, an altered balance between the vasoconstrictive influence of the sympathoadrenergic system and the vasodilatory action of NO‐dependent vascular relaxation may be of importance in the development of sustained hypertension in OSA.
Polygraphic findings in young infants with Joubert's syndrome
Authors: SCHLÜTER B. , BUSCHATZ D. , TROWITZSCH E. , ANDLER W. , AKSU F. , STUTE M.
Published: January 2009

SUMMARY  In three young infants with Joubert's syndrome polygraphic recordings were carried out in the awake state and during REM and NREM sleep in order to characterize the respiratory disorder associated with this condition.

In all three states disturbed respiration parameters were found in variable amounts. The highest breath rate occurred in the awake state followed by REM and NREM sleep. The highest incidence of apnoea and periodic breathing was observed in NREM sleep, followed by REM sleep and the awake state.
Polysomnographic recordings of respiratory disturbances in Rett syndrome
Authors: SCHLÜTER B. , AGUIGAH G. , BUSCHATZ D. , TROWITZSCH E. , AKSU F.
Published: January 2009

SUMMARY Polygraphic recordings in the awake state and during sleep were performed in two girls with Rett syndrome, aged 9 y and 17 y, in order to characterize the clinically manifest breathing disorder of these patients.

Primary hyperventilation was detected, leading to hypocapnia and compensatory apnoea. Hypoxaemia occurred as the consequence of prolonged apnoea. In the younger patient these disturbances were observed only in the awake state, whereas in the older patient they were found in the awake state and during sleep.
Changes in upper airway resistance during progressive normocapnic hypoxia in patients with obstructive sleep apnoea syndrome
Authors: TAFIL‐KLAWE MALGORZATA , KLAWE J. J. , GROTE L. , SCHNEIDER H. , PETER J. H. , ŚMIETANOWSKI M.
Published: January 2009

SUMMARY  The responses of the upper airway to progressive normocapnic hypoxia were studied in 6 healthy men and in 6 patients with obstructive sleep apnoea syndrome (OSAS). The upper airway resistance was calculated by the ratio of the laryngeal pressure (measured using a catheter introduced into oesophagus) to the inspiratory flow. Additionally, genioglossal EMG activity (GG‐EMG) was measured and analysed. The changes of all variables were analysed individually for each subject. The OSAS patients showed reduced ventilatory response, GG‐reactivity and changes in upper airway resistance during progressive hypoxia. It is concluded that impaired reactivity to hypoxic activation (probably due to the process of adaptation of carotid chemoreceptors to nocturnal hypoxia), might reduce the defence abilities of OSAS patients against episodes of obturation in upper airway and obstructive apnoea events.
Speed and direction of shift rotation
Authors: KNAUTH PETER
Published: January 2009

SUMMARY  This review paper deals with the issue of shift rotation, i.e. the number of consecutive shifts of the same type and the order of change between shifts. To minimize the disturbances of the circadian system and the accumulation of sleep deficits, rapidly and clockwise‐rotating shift systems would seem to be preferable. Regarding consecutive night shifts, a week of night shifts seems to be the worst system with regard to performance and accidents. There is a lack of reliable data on the effects of permanent vs. rotating‐shift systems on alertness, performance and accidents. This is also true for the comparison of forward (delaying) and backward (advancing) rotating‐shift systems, although the former would seem to be associated with fewer problems. For both systems, controlled longitudinal studies are necessary.
Extended workshifts and excessive fatigue
Authors: ROSA ROGER R.
Published: January 2009

SUMMARY  Studies of overtime have pointed to fatigue as a potential factor producing, for example, a three‐fold increase in accident rate after 16 h of work, increases in back injuries, hospital outbreaks of bacterial infection, or nuclear‐power plant safety compromises. Fatigue has been measured more directly in studies of scheduled long workshifts, where performance decrements in both work‐related tasks and laboratory‐type behavioural tests have been observed, and significant loss of sleep and increases in subjective sleepiness have been reported. Analyses of accidents or injuries during scheduled extended workshifts, however, have produced equivocal results. Factors which could compound the fatiguing effects of extended workshifts, such as workload, noise, chemical exposure, or duties and responsibilities outside of the workplace, rarely have been studied systematically. It is concluded that extended workshift schedules should be instituted cautiously and evaluated carefully, with appropriate attention given to staffing levels, workload, job rotation, environmental exposures, emergency contingencies, rest breaks, commuting time, and social or domestic responsibilities.
Alertness management: strategic naps in operational settings
Authors: ROSEKIND MARK R. , SMITH ROY M. , MILLER DONNA L. , CO ELIZABETH L. , GREGORY KEVIN B. , WEBBON LISSA L. , GANDER PHILIPPA H. , LEBACQZ J. VICTOR
Published: January 2009

SUMMARY  Managing fatigue in complex operational settings requires attention to multiple factors, including hours of service, scheduling, education and training, countermeasures, technology, and research. Alertness‐management strategies can be used to promote safety, performance, and productivity in operational settings. These strategies can involve both preventive (used prior to duty/shift) and operational (used during duty/shift) approaches. Studies have demonstrated the effectiveness of naps to improve subsequent performance and alertness. Strategic naps can be used effectively to promote performance and alertness in operational settings. Two potential negative effects of naps, sleep inertia and effects on subsequent sleep periods, are discussed. Sleep inertia can involve sleepiness and decreased performance immediately upon awakening from a nap. It should be a consideration prior to implementing nap strategies in work environments. A study of planned rest periods in long‐haul flight operations demonstrated the effectiveness of in‐flight naps to promote performance and alertness during subsequent critical phases of flight (descent and landing). Empirical evaluation of alertness‐management strategies during regular operations will be critical to their implementation. Combining strategies may be the most effective approach to managing fatigue engendered by 24‐h operational demands. Other considerations prior to implementing alertness‐management strategies in operational environments are discussed.
Implementation of napping In industry and the problem of sleep inertia
Authors: MUZET A. , NICOLAS A. , TASSI P. , DEWASMES G. , BONNEAU A.
Published: January 2009

SUMMARY  It seems reasonable to believe that in specific situations napping at the work place would be possible and used if authorized and encouraged. Very short naps could have very positive long‐term effects on biological functions. Training someone to sleep for short periods appears feasible if there is a high motivation to do so. Sleep inertia can be considered as one of the main limiting factors in napping strategy. Sleep inertia depends on different factors such as sleep stage preceding the awakening, temporal placement of the nap, duration of nap and wakefulness preceding it, etc. The effects of sleep inertia might be different depending on the type of task, and a reactivation technique applied immediately after awakening may remove it. Despite the fact that its implementation in industry raises some practical issues, napping can be considered as a possible strategy to increase the vigilance level of night workers.
Melatonin and adjustment to phase shift
Authors: ARENDT JOSEPHINE , DEACON STEVEN , ENGLISH JUDIE , HAMPTON SHELAGH , MORGAN LINDA
Published: January 2009

SUMMARY  The pineal hormone melatonin has clear circadian phase‐shifting effects in humans which have recently been formalized as a phase response curve. Its potential use in circadian rhythm disorders has been investigated in field studies of jet lag and shift work and in simulated phase shift. A substantial amount of information indicates that in the majority of subjects it hastens adaptation of both subjective and objective measures to forced shifts in time cues with few reported side‐effects. Field studies of its use in adaptation to shift work are sparse and preliminary but the first indications are positive. In some blind subjects with sleep disturbance it can stabilize sleep onset time without necessarily entraining all circadian rhythms and it can advance sleep timing in delayed sleep‐phase insomnia. Acute suppression of core body tempera‐ture may be an integral part of the phase‐shifting mechanism.
Ribosomal protein L3 bound to 23S precursor rRNA stimulates its maturation by Mini‐III ribonuclease
Authors: Redko Yulia , Condon Ciarán
Published: January 2009

Ribosomal RNAs (rRNAs) are processed from larger primary transcripts in every living system known. The maturation of 23S rRNA in Bacillus subtilis is catalysed by Mini‐III, a member of the RNase III family of enzymes that lacks the characteristic double‐stranded RNA binding domain of its relatives. We have previously shown that Mini‐III processing of 23S precursor rRNA in assembled 50S ribosomal subunits is much more efficient than a substrate with no ribosomal proteins bound, suggesting that one or more large subunit proteins act as a cofactor for Mini‐III cleavage. Here we show that this cofactor is ribosomal protein L3. Stimulation of the Mini‐III cleavage reaction is through L3 binding to its normal site at the 3′ end of 23S rRNA. We present indirect evidence that suggests that L3 acts at the level of substrate, rather than enzyme conformation. We also discuss the potential implication of using ribosomal protein cofactors in rRNA processing for ribosome quality control.
Preventive measures in infancy to reduce under‐five mortality: a case–control study in The Gambia
Authors: Rutherford Merrin E. , Dockerty John D. , Jasseh Momodou , Howie Stephen R. C. , Herbison Peter , Jeffries David J. , Mulholland Kim , Adegbola Richard A. , Hill Philip C.
Published: January 2009

Objective  To investigate the relationship between child mortality and common preventive interventions: vaccination, trained birthing attendants, tetanus toxoid during pregnancy, breastfeeding and vitamin A supplementation.

Methods  Case–control study in a population under demographic surveillance. Cases (n = 141) were children under five who died. Each was age and sex‐matched to five controls (n = 705). Information was gathered by interviewing primary caregivers.

Results  All but one of the interventions – whether the mother had received tetanus toxoid during pregnancy – were protective against child mortality after multivariate analysis. Having a trained person assisting at child birth (OR 0.2 95% CI 0.1–0.4), receiving all vaccinations by 9 months of age (OR 0.1; 95% CI 0.01–0.3), being breastfed for more than 12 months (Children breastfed between 13 and 24 months OR 0.1 95% CI 0.03–0.3, more than 25 months OR 0.1 95% CI 0.01–0.5) and receiving vitamin A supplementation at or after 6 months of age (OR 0.05; 95% CI 0.01–0.2) were protective against child death.

Conclusions  This study confirms the value of at least four available interventions in the prevention of under‐five death in The Gambia. It is now important to identify those who are not receiving them and why, and to intervene to improve coverage across the population.