Biomedical subjects

R Cluydts

Publications and source records attributed to R Cluydts.

At least 19 recordsLinked to original sources

PubMed2003

Sleepiness as a state-trait phenomenon, comprising both a sleep drive and a wake drive.

In this paper it is proposed to extend the classical models of sleepiness in two ways. Firstly, the role of a wake drive, besides a sleep drive, in determining sleepiness is emphasised. Although this has already been suggested in literature and convincing arguments can be found, it is not generally accepted. Secondly, we argue to incorporate trait aspects of sleepiness or a long-term person-specific level of sleepiness, besides short-term changes of sleepiness or 'state-sleepiness'. Shortly, a conceptualisation of sleepiness in which situational wake drive and sleep drive modify a basal level of both wake drive and sleep drive, is proposed. It implies that sleepiness can result from essentially different factors involved: a chronic condition or an acute state of either a high level of sleep drive, a low level of arousal or a combination of both. This is illustrated in a working model and potential assessment tools for the wake drive and state versus trait sleepiness are discussed.

Humans↗

PubMed2003

Atypical depression as a secondary symptom in chronic fatigue syndrome.

Chronic fatigue syndrome (CFS) has gained prominence since 1988 and a substantial amount of research has been done in this domain. However, it is still regarded as a controversial condition. Moreover, most of the symptoms of CFS itself are non-specific, occurring in many illnesses; some of the symptoms are also common in depression. Indeed, an area of continued controversy and debate involves the diagnostic overlap between CFS and psychiatric disorders. Through anecdotal evidence, atypical depression appears to be common in CFS. Recent developments in psychobiology underscore the role of the acute phase response and its associated sickness behavior in affective disorders. Thus, we hypothesize that atypical depression is sickness behavior rather than an affective disorder as shown by anecdotal evidence in CFS.

Acute-Phase Reaction↗

PubMed2003

The challenge of chronic insomnia: is non-nightly hypnotic treatment a feasible alternative?

The adverse effects of insomnia on health and quality of life are matters receiving increasing attention. Yet, surveys have consistently shown that most people suffering from insomnia do not seek medical help, perhaps, in part, because of a concern of becoming dependent on hypnotic medication. The treatment of chronic insomnia poses a particular dilemma in that continuous hypnotic treatment is restricted in many countries to a maximum of 4 weeks, and behavioural treatment is not readily available. Non-nightly hypnotic treatment of chronic insomnia offers a promising alternative option for the many patients whose symptoms do not necessitate nightly drug intake, allaying fears of psychological dependence on medication and respecting regulatory constraints on hypnotic use while providing patients with adequate symptom relief. The practical feasibility and efficacy of this approach has been demonstrated with zolpidem using various treatment regimens and study designs. So far, six clinical trials have been completed on over 4000 patients. Published results show effective treatment of insomnia without any evidence of either adverse event associated with a discontinuous regimen or increased hypnotic use over the treatment period.

Humans↗

PubMed2002

Continuous versus non-nightly use of zolpidem in chronic insomnia: results of a large-scale, double-blind, randomized, outpatient study.

New treatment strategies are encouraged in insomnia and, in particular, discontinuous treatment. The aim of this double-blind study was to compare, in a large primary care population of chronic insomniacs (> 4 weeks duration) the efficacy and safety of zolpidem 10 mg 5 nights/week and placebo 2 nights/week, to that of nightly zolpidem. Seven hundred and eighty-nine drug-free insomniacs, with a Total Sleep Time (TST) of 3-6 h/night were enrolled in seven European countries. After a placebo run-in period, treatment lasted 14 days. The primary criterion was the Clinical Global Impression improvement score (CGI-II) which showed that 65.2% of patients in the continuous and 58.6% in the discontinuous groups were rated 'much' or 'very much' improved. Even though the non-inferiority test did not show the equivalence of both regimens, the difference of 7% in responder rates does not appear to be clinically relevant. Other sleep parameters such as TST, number of nocturnal awakenings and Quality of Life scales showed marked, not significantly different, improvements in both groups. Both regimens were well tolerated and no adverse event which could be related to non-treatment nights was reported in the discontinuous group. Non-nightly zolpidem appears to be a feasible and safe additional option for the management of chronic insomnia.

Adolescent↗

PubMed2001

Neuropsychological functioning in chronic fatigue syndrome: a review.

OBJECTIVE: In this paper we review critically the current status of neurocognitive studies in patients with chronic fatigue syndrome (CFS). METHOD: CFS literature was monitored as part of a large research project which involved several neuropsychological and psychopathological studies. The literature survey was the result of several consecutive searches on Medline and PsycInfo databases. RESULTS: The neurocognitive studies are reviewed in terms of scientificaly accepted aspects of attention and memory. In addition, we review possible explanations for cognitive dysfunction in CFS. This is preceded with a discussion of the methodological limitations that are considered to explain inconcistencies across neuropsychological studies in CFS. CONCLUSION: The current research shows that slowed processing speed, impaired working memory and poor learning of information are the most prominent features of cognitive dysfunctioning in patients with CFS. Furthermore, to this date no specific pattern of cerebral abnormalities has been found that uniquely characterizes CFS patients. There is no overwhelming evidence that fatigue is related to cognitive performance in CFS, and researchers agree that their performance on neuropsychological tasks is unlikely to be accounted solely by the severity of the depression and anxiety.

Attention↗

PubMed2001

Slow-release caffeine as a countermeasure to driver sleepiness induced by partial sleep deprivation.

The effect of partial sleep deprivation (PSD) on driving abilities, as measured with a driving simulator, and the value of slow-release caffeine as a countermeasure to the expected performance decrements, were studied. Twelve subjects, between 20 and 25 years of age, underwent four experimental conditions, 4.5 or 7.5 h time in bed (TIB) with 300 mg slow-release caffeine or placebo, according to a Latin square design. Driving performance was measured twice by a 45-min driving task on a simulator. Subjective sleepiness/alertness and mood were assessed four times, by means of the Stanford Sleepiness Scale (SSS) and Profile of Mood States (POMS). After 4.5 h as compared with 7.5 h TIB lane drifting and speed deviation were higher, but only the effect on the first variable reached significance. In the placebo condition at 13.00 h, accident liability increased after PSD. Subjective sleepiness was higher in the 4.5 h TIB group. Caffeine intake gave rise to a decrease in lane drifting and after PSD it led to a smaller speed deviation and accident liability. The findings suggest that a lack of sleep can lead to a significant driving performance impairment, with drivers having problems to maintain an appropriate road position and a posted speed and more drivers getting involved in an accident. Secondly, the results indicate that caffeine - more specifically slow-release caffeine - can serve as a valuable countermeasure to these performance decrements, in the absence of any important side-effects, especially when its application is of an acute nature and when there is no opportunity to take a nap.

Adult↗

PubMed2000

How significant are primary sleep disorders and sleepiness in the chronic fatigue syndrome?

In order to study both the prevalence of Primary Sleep Disorders (PSD) and sleepiness, and their association to the Chronic Fatigue Syndrome (CFS), 46 unselected outpatients (34 women, mean age 36.5) were examined clinically and underwent two nights of all-night polysomnography and multiple sleep latency tests (MSLT). Forty-six percent presented with a Sleep Apnea/Hypopnea Syndrome Index (AHI>=5), 5% with a Periodic Limb Movements syndrome. No subject received a diagnosis of Narcolepsy or Idiopathic Hypersomnia. Thirty percent showed the presence of objective sleepiness as measured by MSLT<10 minutes. Objective and subjective measures of sleepiness were not associated with CFS, nor with the double diagnosis of CFS and a PSD. The presence of PSD or sleepiness was not associated with any of the clinical scales that were used to measure anxiety, depression, somatisation, physical or mental fatigue, or functional status impairment. Fifty-four percent of CFS patients had no PSD, and 69% no sleepiness. These patients could not be distinguished clinically from patients having a PSD or from those with sleepiness. Therefore, it is unlikely that CFS is simply a somatic expression of any PSD observed in our sample or of sleepiness per se.

Adult↗

PubMed1999

Attention and information processing efficiency in patients with Chronic Fatigue Syndrome.

In this study a battery of attentional tests and a verbal memory task were administered to outpatients with Chronic Fatigue Syndrome (CFS) in order to evaluate aspects of attention that have not been explored in this group to date. In addition, this study was designed to further examine memory function and to extend the few reports investigating the rate of cognitive processing independent of motor speed and the possibility of a modality-specific impairment of information processing. Twenty-nine patients with CFS and 22 healthy controls matched for age, gender, intelligence, and education were included in this study. The results show that patients with CFS do not seem to be impaired for modification of phasic arousal level, nor for visual selective attention requiring shifting of attention in the visuospatial field. The results further support the presence of reduced information processing speed and efficiency, and strengthen the evidence of a global non-modality-specific attentional dysfunction in patients with CFS. In this study the poor performance of patients with CFS on recall of verbal information was due to poor initial storage rather than to a retrieval failure.

Adult↗

PubMed1998

Attention and verbal learning in patients with chronic fatigue syndrome.

Former neuropsychological studies with Chronic Fatigue Syndrome (CFS) patients evaluated a broad range of cognitive functions. Several, but not all, reported subtle attentional and memory impairments suggesting possible mild cerebral involvement. In this study, a battery of attentional tests and a verbal memory task were administered to 20 CFS patients and 22 healthy controls (HC) in order to clarify the specific nature of attention and memory impairment in these patients. The results provide evidence for attentional dysfunction in patients with CFS as compared to HC. CFS patients performed more poorly on a span test measuring attentional capacity and working memory. Speeded attentional tasks with a more complex element of memory scanning and divided attention seem to be a sensitive measure of reduced attentional capacity in these patients. Focused attention, defined as the ability to attend to a single stimulus while ignoring irrelevant stimuli, appears not to be impaired. CFS patients were poorer on recall of verbal information across learning trials, and poor performance on delayed recall may be due to poor initial learning and not only to a retrieval failure.

Adult↗

PubMed1997

Cluster analytic validation of the DSM melancholic depression. The threshold model: integration of quantitative and qualitative distinctions between unipolar depressive subtypes.

Cluster analysis was performed on the DSM-III symptoms of major depression and symptoms of melancholia identified in a study group consisting of 220 unipolar depressed inpatients a melancholic and non-melancholic cluster. Patients allocated to the melancholic cluster were more severely depressed and they were characterized by psychomotor disorders, a distinct quality of mood, diurnal variation, early morning awakening, and non-reactivity. Our results support the construct validity of the DSM-III melancholic subtype of major depression. This study supports the integrated threshold model:. (i) melancholic and non-melancholic depression may be regarded as continuous classes in terms of overall severity of depression; and (ii) both groups form discrete categories with regard to the melancholic symptoms, which emerge as the severity of depression increases.

Adjustment Disorders↗

PubMed1997

Cerebral blood flow related to induction of a depressed mood within and out of the realm of attention in normal volunteers.

The effects of a depressed mood on regional cerebral blood flow (rCBF) were measured after a mood-induction procedure (MIP) in normal volunteers. The MIPs were administered 'within the realm of attention' and 'out of the realm of attention'. A modified Velten procedure, which consisted of tape-recorded self-referent depressive statements, was used for mood induction. For the induction out of the realm of attention, a combination of dichotic listening and subliminal stimulation was used. A neutral induction procedure served as a control condition. CBF was measured with Tc-99m HMPAO single photon emission computed tomography (SPECT) with regard to 14 healthy female students. Scores on mood rating scales showed negative changes after both MIPs. Statistical analyses revealed lateralized changes in rCBF in the thalamus. Decreased thalamic CBF in the right hemisphere was demonstrated after both MIPs compared with the neutral induction condition. Moreover, hippocampal rCBF increased significantly, but only after induction out of the realm of attention. These findings suggest both hippocampal and thalamic involvement in the regulation of mood experience.

Adult↗

PubMed1997

Physical fatigability and exercise capacity in chronic fatigue syndrome: association with disability, somatization and psychopathology.

Physical fatigability and avoidance of physically demanding tasks in chronic fatigue syndrome (CFS) were assessed by the achievement or nonachievement of 85% of age-predicted maximal heart rate (target heart rate, THR) during incremental exercise. The association with functional status impairment, somatization, and psychopathology was examined. A statistically significant association was demonstrated between this physical fatigability variable and impairment, and a trend was found for an association with somatization. No association was demonstrated with psychopathology. These results are in accordance with the cognitive-behavioral model of CFS, suggesting a major contribution of avoidance behavior to functional status impairment; however, neither anxiety nor depression seem to be involved in the avoidance behavior. Aerobic work capacity was compared between CFS and healthy controls achieving THR. Physical deconditioning with early involvement of anaerobic metabolism was demonstrated in this CFS subgroup. Half of the CFS patients who did not achieve THR did not reach the anaerobic threshold. This finding argues against an association in CFS between avoidance of physically demanding tasks and early anaerobic metabolism during effort.

Adult↗

PubMed1997

Construct validity of the Beck Depression Inventory in a depressive population.

This study investigates the construct validity of the Beck Depression Inventory (BDI) in a large population of DSM-III unipolar depressive inpatients. The BDI correlates weakly with the Hamilton scale and differentiates between minor, major and melancholic/psychotic unipolar depressive subgroups. Factor analysis of the BDI resulted in psychological/cognitive (BDIPSY) and somatic/vegetative (BDISOM) subscales. The BDISOM subscale displayed a narrower relationship with the depression construct, as evidenced by a better differential validity and by significant effects for the DST non-suppression response. The present findings generally lend support to the construct validity of the BDI in depressive populations.

Adult↗

PubMed1997

Generalized anxiety disorder in chronic fatigue syndrome.

A structured psychiatric interview, forming part of a global psychopathological approach, revealed higher prevalence rates of current and lifetime psychiatric disorders and a higher degree of psychiatric comorbidity in patients with chronic fatigue syndrome (CFS) than in a medical control group. In contrast to previous studies, a very high prevalence of generalized anxiety disorder (GAD) was found in CFS, characterized by an early onset and a high rate of psychiatric comorbidity. It is postulated that GAD represents a susceptibility factor for the development of CFS. A significantly higher prevalence was also observed for the somatization disorder (SD) in the CFS group. Apart from a higher female-to-male ratio in fibromyalgia, no marked differences were observed in sociodemographic or illness-related features, or in psychiatric morbidity, between CFS patients with and without fibromyalgia. CFS patients with SD have a longer illness duration and a higher rate of psychiatric comorbidity. These findings are consistent with the suggestion of Hickie et al. (1) that chronic fatigued subjects with SD should be distinguished from subjects with CFS.

Adult↗

PubMed1997

Sleep anomalies in the chronic fatigue syndrome. A comorbidity study.

Polysomnographic findings were compared between a group of patients with the chronic fatigue syndrome (CFS; n = 49) and a matched healthy control (HC) group (n = 20). Sleep initiation and sleep maintenance disturbances were observed in the CFS group. The percentage of stage 4 was significantly lower in the CFS group. A discriminant analysis allowed a high level of correct classification of CFS subjects and HC. Sleep-onset latency and the number of stage shifts/hour contributed significantly to the discriminant function. The presence of these anomalies as well as the decrease in stage 4 sleep were not limited to the patients also diagnosed with fibromyalgia or with a psychiatric disorder. No association was found between sleep disorders and the degree of functional status impairment. The mean REM latency and the percentage of subjects with a shortened REM latency were similar in CFS and HC.

Adult↗

PubMed1997

Psychomotor and cognitive performance in nonapneic snorers: preliminary findings.

Snoring is a common phenomenon and a primary symptom in obstructive sleep apnea syndrome, a sleep-related breathing disorder in which neuropsychological function is reported to be impaired. The first purpose of the present study was to compare cognitive and motor function in 25 heavy nonapneic snorers and 26 sleep apneics. As the basis for impairments in heavy nonapneic snorers is still unclear, the influence of nighttime breathing disturbances and morning alertness, respectively, on daytime performance was evaluated too. Nonapneic snorers exhibit more slow wave sleep and tend to have fewer changes in sleep stage than sleep apnea patients, but values for other sleep variables are similar. Snorers also show comparable alertness. Deficits in immediate visual memory and in visuospatial reasoning are not found. However, there are some indications that snorers show decreased manual dexterity and eye-hand coordination for the nonpreferred hand and that they have deficits in focused attention. In addition, snorers may show difficulties in finger-tapping speed. These performance measures tend to be associated with reduced morning alertness, except for the score on focused attention which has a tendency to be related to the nocturnal breathing disturbances.

Adult↗

PubMed1996

Technetium-99m hexamethylpropylene amine oxime single-photon emission tomography of regional cerebral blood flow in insulin-dependent diabetes.

The study was performed to investigate subclinical abnormalities in regional cerebral blood flow (rCBF) in patients with insulin-dependent diabetes mellitus (IDDM) and to correlate them with patients characteristics. After intravenous injection of technetium-99m hexamethylpropylene amine oxime (HMPAO), tracer uptake of the prefrontal, frontal and parieto-occipital zones was measured with a triple-head single-photon emission tomography (SPET) camera system in 35 IDDM patients outside an episode of hypoglycaemia. Tracer uptake values in 16 age- and sex-matched healthy volunteers served as reference values. Compared with healthy subjects, increased tracer uptake of both prefrontal regions and the left frontal region could be shown in diabetes. Tracer uptake was negatively correlated with the duration of diabetes in all investigated regions. In diabetic patients with a disease duration of more than 5 years (n=26), stepwise regression analysis revealed a significant positive correlation between their HbA1c levels and tracer uptake. Long-term diabetic patients with reduced (pre)frontal tracer uptake (n=8) had lower HbA1c levels than those without (8.4%+/-0.2% vs 9.3%+/-0.3%, P<0.05) and tended to have more frequently a history of hypoglycaemic coma (6/8 vs 6/18, P=0.06). It can be concluded that duration of diabetes contributes to subclinical changes in basal rCBF in IDDM as detected with HMPAO SPET of the brain. The positive correlation between the presence of regional hypoperfusion and lower HbA1c levels in long-term diabetic patients may be interpreted in the light of a presumed higher incidence of hypoglycaemia as metabolic control improves.

Adult↗

PubMed1996

Effects of affective-semantic mode of item presentation in balanced self-report scales: biased construct validity of the Zung Self-rating Depression Scale.

The widely applied procedure of balancing self-report instruments by including positively and negatively keyed items is exemplified by the Zung Self-rating Depression Scale (SDS). Investigation of the influence of the symptom-positive and symptom-negative item modes on the SDS in a depressed population resulted in two major findings. First, the reversed scoring of the symptom-negative items resulted in higher mean item scores. Secondly, factor analyses of the SDS in the present study and in previous research revealed that the semantic modes of item presentation were represented in the factor structure of the SDS. These findings were confirmed by analyses with the State-Trait Anxiety Inventory (STAI) and by previous factor analytical research with balanced instruments and were interpreted within the framework of the theory of Positive and Negative Affect. The present data cast doubts on the construct validity of the SDS as a measure of depressive symptomatology due to the presence of the negatively keyed items and suggest reconsideration of the use of balanced instruments for minimization of the acquiescence response set.

Adult↗