Raymond Cluydts

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.

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.

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).

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.

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.

Cognitive Functioning in Patients with Chronic Fatigue Syndrome

A comprehensive battery of neuropsychological tests was administered to 35 outpatients suffering from Chronic Fatigue Syndrome (CFS). They were compared to 33 normal controls matched for age, gender, intelligence, and education. The patients displayed psychomotor slowing and impaired attention. The learning rate of verbal and visual material for patients with CFS was slower, and delayed recall of verbal and visual information was impaired. Because there was a high variability in cognitive impairment within the CFS group, it would be inappropriate to generalize results to the entire CFS population. Two neuropsychological variables indicating aspects of psychomotor performance and verbal memory were found to discriminate best between patients and controls.

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.