PubMed Health⌕ Search

Biomedical subjects

Raymond Cluydts

Publications and source records attributed to Raymond Cluydts.

14 recordsLinked to original sources
PubMed2006

Neurophysiological aspects of primary insomnia: implications for its treatment.

Insomnia has usually been studied from a behavioral perspective. Somatic and/or cognitive conditioned arousal was shown to play a central role in sleep complaints becoming chronic, and was used as a starting point for the development of treatment modalities. The introduction of the neurocognitive perspective, with its focus on cortical or CNS arousal, has given rise to a renewed interest in the neurophysiological characteristics of insomnia. Recent research, using quantitative EEG, neuroimaging techniques and the study of the microstructure of sleep, suggests a state of hyperarousal with a biological basis. Furthermore, insomnia might not be restricted to sleep complaints alone because it appears to be a 24-h disorder, affecting several aspects of daytime functioning as well. These new findings have implications for the treatments used and indicate that a focus on cortical or CNS arousal should be pursued. As such, the use of EEG neurofeedback, a self-regulation method based on the paradigm of operant conditioning, might be a promising treatment modality. Preliminary results for insomnia and successful applications for other disorders suggest that this treatment can have the necessary stabilizing effects on the EEG activity, possibly resulting in a normalizing effect on daytime as well as nighttime functioning.

Arousal↗
PubMed2006

Multidimensional scaling of pediatric sleep breathing problems and bio-behavioral correlates.

STUDY OBJECTIVES: Complex relationships exist between pediatric sleep disorders and daytime behavior. Using a multidimensional scaling model, we investigated these relationships in 126 children with sleep breathing disorders (SBD). METHOD: Validated questionnaires on nighttime behavior, daytime behavior, and respiratory health were administered to a large number of school children in Belgium. Children who met the criterion of having at least one sleep-related breathing problem (three or more times per week during the past six months) were selected for further analyses. A total of 26 indicators were defined and modeled, including sleep problems, sleep efficiency, sleep environment, sleep enuresis, internalised and externalised behavioral problems, respiratory health of the child and relatives, smoking exposure, and caffeine consumption. RESULTS: From 3,045 questionnaire responses 4.1% of the children were reported to have a SBD symptom. SBD children differed on sleep and health domains from non-SBD children. Furthermore, through scaling of the (dis)similarities among the 26 indicators the SBD child was able to be modeled. By way of an internal analysis of the data-matrix the following indicators were eliminated: sleep correlates, health of the family, and behavior rated by teachers, followed by caffeine intake, drugs, and behavior rated by the parents. This revealed a two-dimensional model, consisting of primary SBD and secondary SBD. CONCLUSION: Children with SBD differ on many domains from children without such disorders and an underlying two-fold SBD concept was found. Firstly, the SBD-indicator positioned in between investigated correlates with disorders of initiating and maintaining sleep and sleep hyperhydrosis on one hand and with respiratory-related illnesses on the other; this was labeled primary SBD. Secondly, the SDB-indicator not closely associated with any of the investigated correlates can be interpreted as secondary SBD.

Child↗
PubMed2006

Individualized and time-variant model for the functional link between thermoregulation and sleep onset.

This study makes use of control system model identification techniques to examine the relationship between thermoregulation and sleep regulation. Specifically, data-based mechanistic (DBM) modelling is used to formulate and experimentally test the hypothesis, put forth by Gilbert et al., that there exists a connection between distal heat loss and sleepiness. Six healthy sleepers each spent three nights and the following day in the sleep laboratory: an adaptation, a cognitive arousal and a neutral testing day. In the cognitive arousal condition, a visit of a television camera crew took place and subjects were asked to be interviewed. During each of the three 25-min driving simulator tasks per day, the distal-to-proximal gradient and the electroencephalogram are recorded. It is observed from these experimental data that there exists a feedback connection between thermoregulation and sleep. In addition to providing experimental evidence in support of the Gilbert et al. (2004) hypothesis, the authors propose that the nature of the feedback connection is determined by the nature of sleep/wake state (i.e. NREM sleep versus unwanted sleepiness in active subjects). Besides this, an individualized and time-variant model for the linkage between thermoregulation and sleep onset is presented. This compact model feeds on real-time data regarding distal heat loss and sleepiness and contains a physically meaningful parameter that delivers an individual- and time-depending quantification of a well known biological features in the field of thermoregulation: the thermoregulatory error signal T(hypo)(t)-T(set)(t). A validation of these physical/biological features emphasizes the reliability and power of DBM in describing individual differences related to the sleep process.

Body Temperature Regulation↗
PubMed2005

Odds, prevalence and predictors of sleep problems in school-age normal children.

The objectives of the study were to describe the prevalence, odds, and predictors of 36 paediatric sleep behaviours and describe their coexistence in a school-age normal population. The design was community-based questionnaire survey of sleep-wake patterns, sleep environment, and 36 sleep behaviours indicative of six sleep disorder-subscales using the Health-Behaviour Questionnaire. A caregivers' report of 3045 children aged 6-13 years in Belgium constituted the participants. Prevalence of each sleep behaviour was calculated. Log-linear modelling within and between the sleep disorder-subscales was used to screen for coexistence. The effect size of selected night-time parameters to the likelihood of sleep behaviours and disorder-subscale was expressed as odds ratios via logit regression analysis. Significant differences in sleep-wake patterns were found between weekday and weekend. Ranking by odds showed that: (1) sleep problems such as 'tired when waking up', 'repetitive limb movements', 'going to bed reluctantly', and 'sleep paralysis' and; (2) the disorder-subscale 'excessive somnolence' are common in children. Coexistences within and between disorder-subscales of sleep problems are evident in a school-age, normal population. These results suggest that disorders of excessive somnolence (DES) are highly prevalent in a non-clinical sample of school-age children. Furthermore, sleep-onset latency and a noisy, not well-darkened room are predictive towards the odds for exhibiting sleep problems and disorders. It is advocated that more information on the importance of good sleep-wake hygiene should reach parents and children.

Adolescent↗
PubMed2004

Executive function in sleep apnea: controlling for attentional capacity in assessing executive attention.

STUDY OBJECTIVES: As the effects of general slowness and decreased attentional capacity on higher executive attention have not been fully taken into account in the sleep apnea literature, we statistically controlled for basic attentional performance in evaluating executive attention per se in sleep apnea patients. DESIGN: A case-controlled design was used with comparison of basic and executive attentional tasks. PARTICIPANTS: Thirty-six polysomnographically diagnosed patients (mean apnea-hypopnea index = 60.5 +/- SD 31.6) participated, together with 32 healthy controls. MEASUREMENTS AND RESULTS: Neuropsychological tests included Trail Making part A and B, Symbol Digit Modalities (SDMT), Digit Span forward and backward, Stroop Color-Word, Five-Point design fluency, and an Attentional Flexibility task. Patients' vigilance data indicated time-on-task decrements after 10 minutes. Moreover, their performance was significantly reduced on the SDMT (effect size d = 0.93), the Digit Span forward task (d = 0.44), the number of errors on the basic 2-choice reaction time subtest of the Attentional Flexibility task (d = 0.74) and the mean RT on the actual Attentional Flexibility subtest (d = 0.54). It has been argued that the latter poor performance was probably primarily related to the task's phonologic loop component of working memory rather than to an attentional switching deficit per se. No other performance differences were found between patients and healthy controls. CONCLUSIONS: In addition to vigilance decrements, attentional capacity deficits clearly emerge, ie, slowed information processing and decreased short-term memory span. However, no specific clinical indications for executive attentional deficits--such as disinhibition, distractibility, perseveration, attentional switching dysfunction, decreased design fluency, or an impaired central executive of working memory--are found in patients with severe sleep apnea. Their cognitive performance seems very similar to the cognitive decline found after sleep loss and qualitatively different from patients with chronic obstructive pulmonary disease, suggesting sleepiness as the primary factor in a parsimonious explanation for the attention deficits in sleep apnea, without the need to assume prefrontal brain damage.

Attention↗
PubMed2004

Pediatric sleep disorders: exploratory modulation of their relationships.

STUDY OBJECTIVES: This study explores relationships between clinically encountered sleep problems in children. DESIGN: The Sleep Disturbance Scale for Children (SDSC) (Bruni et al 1996), which screens 26 sleep problems and results in 6 sleep disorder-subscales, was used as core in a larger health-behavior questionnaire (HBQ). PARTICIPANTS: Caregivers of 3045 6- to 12-year-olds filled out the HBQ. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: 21 SDSC-items plus 15 new sleep items were selected. Via structural equation modelling we explored (1) relations within and between disorder-subscales, (2) relations between the disorder-subscales with 3 indexes added (i.e., sleep efficiency index, sleep environment index, and sleep enuresis) and (3) relations of the disorder-subscales to their categorization: dyssomnia and parasomnia, without and with the indexes. CONCLUSIONS: The final model had a satisfying fit and approximates the Association of Sleep Disorders Centers' classification. Each disorder-subscale can be applied individually. However, some items are statistically of low value. For that reason, the use as the inference of relations between such items should be cautious. Adding the 3 indexes improved the fit of the model. The complexity of 'sleep enuresis' was especially revealed. For the practicing care provider, as for researchers, the statistical model proposed could be a valuable directive in the diagnostic classification process of pediatric sleep problems.

Adolescent↗
PubMed2004

Executive control of attention in sleep apnea patients: theoretical concepts and methodological considerations.

Sleep apnea patients' nocturnal breathing disturbances cause daytime sleepiness and cognitive impairments. Attentional capacity and vigilance deficits have often been observed. Moreover, some studies have suggested executive dysfunction, usually assumed to be related to (pre)frontal lobe dysfunction caused by intermittent hypoxemia. However, sleep disruption itself has a pervasive influence on cognitive function and affects not only underlying 'lower-level' processes such as arousal and alertness, but also 'higher-level' cognitive processes such as executive attention. This methodological caveat has not been fully taken into account in the sleep apnea literature. In order to be able to disentangle these cognitive processes on different levels, sound theoretical neurocognitive frameworks are needed to attain careful analyses and interpretations of neuropsychological data. Therefore, this paper firstly presents an overview of relevant theoretical concepts and models of arousal, attention, and executive function. Then, it is being argued that these theoretical considerations have important methodological implications. These methodological concerns are being addressed by specific experimental and statistical approaches, illustrated by some well-known neuropsychological tests. It can be concluded that the reported executive deficits in sleep apnea patients should be regarded as tentative, and that more case-controlled studies are needed using fine-grained analyses to parcel complex cognitive abilities into their subcomponents.

Arousal↗
PubMed2004

Effect of cognitive arousal on sleep latency, somatic and cortical arousal following partial sleep deprivation.

Emerging research has shown that sleepiness, defined as the tendency to fall asleep, is not only determined by sleep pressure and time of day, but also by physiological and cognitive arousal. In this study we evaluated (i) the impact of experimentally induced cognitive arousal on electroencephalogram (EEG) defined sleep latency, and subjective, somatic and cortical arousal, and (ii) whether experimentally induced cognitive arousal enhances performance on a driving simulator test. Twelve healthy sleepers each spent three nights and the following day in the sleep laboratory: an adaptation, a cognitive arousal and a neutral testing day. In the cognitive arousal condition, a visit of a television camera crew took place and subjects were asked to be interviewed. On each testing day, a 5-min heart rate recording, subjective sleepiness and arousal scales, Multiple Sleep Latency Test and a 25-min driving simulator task were scheduled three times at 2-h intervals. Experimentally induced cognitive arousal resulted in significant increases in objective sleep latency. Significantly elevated levels of subjective and somatic arousal--as indexed by a subjective arousal scale and heart rate--were also evidenced following cognitive arousal induction. A marginally significant trend for increased cortical arousal, measured by EEG beta activity, was also found. No effects were found on driving simulator performance. These findings support the concept of cognitive arousal as a significant component in determining sleep latency. In addition, it was illustrated that cognitively induced arousal can provoke increases in somatic and possibly even cortical arousal in normal sleepers. However, this was not accompanied by an enhanced ability to perform adequately on a driving simulator test.

Adaptation, Physiological↗
PubMed2004

Zolpidem 'as needed': methodological issues and clinical findings.

This article introduces 'as needed' hypnotic treatment as a possible option in the psychopharmacological treatment for chronic but non-daily occurring insomnia complaints. This treatment option is a well-structured regimen designed by both patient and treating physician. It aims at providing symptomatic relief for sleepless nights and preventing the development of possible dependence on the hypnotic agent. A significant amount of responsibility regarding the necessary accompanying lifestyle changes remains in the patient's hands. This paper describes three of the early experiments designed as a 'proof of concept'. All three studies demonstrated that zolpidem can be used effectively and safely on a non-daily basis in individuals with chronic insomnia. Although these studies have methodological limitations, they opened doors to well-designed clinical trials in both in and outpatients. The scientific validation of this therapeutic approach is still in progress. In addition to sleep laboratory studies, ecological studies are needed to investigate pill-taking behaviour and the risk of dependence over a long period of time in real life settings.

Clinical Trials as Topic↗
PubMed2003

Effects of slow-release caffeine and a nap on driving simulator performance after partial sleep deprivation.

A driving simulator was used to evaluate the effectiveness of a 30-min. nap and 300-mg slow-release caffeine as countermeasures to drivers' sleepiness induced by partial sleep deprivation. 12 participants were allowed 45 hr. time in bed at the laboratory. Driving performance then was measured twice--at 9 a.m. and at 1 p.m.--by a 45-min. driving task on a simulator. Subjective sleepiness/alertness and mood were assessed four times on the Stanford Sleepiness Scale and the Profile of Mood States. Driving performance was assessed as Lane Drifting, Speed Deviation, and Accident Liability. A 30-min. nap opportunity and 300 mg of slow-release caffeine both were successful in counteracting drivers' sleepiness. The remedial effect of slow-release caffeine lasted longer than that of the nap, that is, it was also effective in the afternoon session. This suggests that slow-release caffeine represents a valuable countermeasure that, in the case of partial sleep deprivation, is preferred to a nap when sleepiness has to be counteracted for a longer time.

Accidents, Traffic↗
PubMed2002

Attentional switching-related human EEG alpha oscillations.

Alpha oscillations during cognitive performance have mostly been studied in memory and/or basic attention tasks. This study investigates task-related alpha power desynchronization during an attentional switching task requiring higher executive attentional control. Low 8-10 Hz and high 10-12 Hz alpha power responses are studied in good versus poor performers based upon normative data. Accurate, fast and stable performers showed significant task-related desynchronization in the 8-10 Hz range during attentional switching, whereas inaccurate performers hypersynchronized in the 10-12 Hz range, and slow and unstable performers did not demonstrate significant alpha reactivity. These preliminary findings indicate, in agreement with previous research, functional differences in these narrow frequency bands. The 8-10 Hz power decrease is likely to be related to phasic arousal or alertness, whereas the 10-12 Hz power increase appears to be associated with inaccurate attentional switching.

Adult↗
PubMed2002

Daytime sleepiness and its evaluation.

Basic models of sleepiness, focusing on the homeostatic and circadian components of sleepiness, are able to predict important fluctuations of sleepiness. However, they fail in explaining certain sleepiness phenomena, as for instance in insomnia patients. To meet this shortcoming, modern models incorporate the arousal component of sleepiness, in addition to the sleep drive. While these models mainly concentrate on short-term changes in sleepiness, "state" sleepiness, there are indications that a stable characteristic level of sleepiness, "trait" sleepiness, is also an important determinant of a person's level of sleepiness. This leads to a conceptualization of sleepiness in which situational factors modify a basal level of sleep drive and arousal. It implies that sleepiness is not a unitary concept and can reflect essentially different states. Multiple sleepiness assessment tools have been proposed in the past. The majority of them offer valuable information, but they do not grasp all aspects of sleepiness. We should bear in mind that tools for assessing sleepiness are always operationalizations reflecting the theoretical framework the investigator has on sleepiness. Hence, rather than searching for a gold standard for the measurement of sleepiness, future research effort should be aimed at linking the various measurement techniques with the hypothesized underlying components of sleepiness on a sound empirical basis.

Arousal↗