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Biomedical subjects

H A Kamphuisen

Publications and source records attributed to H A Kamphuisen.

At least 19 recordsLinked to original sources
PubMed2000

Analysis of a sleep-dependent neuronal feedback loop: the slow-wave microcontinuity of the EEG.

Increasing depth of sleep corresponds to an increasing gain in the neuronal feedback loops that generate the low-frequency (slow-wave) electroencephalogram (EEG). We derived the maximum-likelihood estimator of the feedback gain and applied it to quantify sleep depth. The estimator computes the fraction (0%-100%) of the current slow wave which continues in the near-future (0.02 s later) EEG. Therefore, this percentage was dubbed slow-wave microcontinuity (SW%). It is not affected by anatomical parameters such as skull thickness, which can considerably bias the commonly used slow-wave power (SWP). In our study, both of the estimators SW% and SWP were monitored throughout two nights in 22 subjects. Each subject took temazepam (a benzodiazepine) on one of the two nights. Both estimators detected the effects of age, temazepam, and time of night on sleep. Females were found to have twice the SWP of males, but no gender effect on SW% was found. This confirms earlier reports that gender affects SWP but not sleep depth. Subjectively assessed differences in sleep quality between the nights were correlated to differences in SW%, not in SWP. These results demonstrate that slow-wave microcontinuity, being based on a physiological model of sleep, reflects sleep depth more closely than SWP does.

Adolescent↗
PubMed1998

[Continued driving habits of patients diagnosed with excessive daytime sleepiness].

OBJECTIVE: Description of driving behaviour of patients with excessive daytime sleepiness (EDS) and the influence on their driving of diagnosis, therapy, legal guidelines and advices. DESIGN: Inventory based on questionnaires. SETTING: Centre for Sleep and Wake Disorders, The Hague, the Netherlands. METHODS: All patients with EDS who were in a stable condition for at least 6 months after therapy were sent a questionnaire (n = 138). The questions concerned actual driving behaviour, EDS and the effects of diagnosis, therapy and advice given by the Centre. RESULTS: The response was 67% (n = 92). Eighteen patients had never driven a car. Eighteen of the other 74 patients quit driving or drove less. Fifty-six patients did not change their behaviour or drove even more. There was little effect on driving behaviour of diagnosis, therapy and advice to stop driving. CONCLUSION: Patients with EDS often participate as drivers in modern traffic. Legal guidelines and advice given by physicians have only little influence on this behaviour. As general measures seem to be ineffective, approaches tailored to the individual patient may lead to more acceptable results.

Adolescent↗
PubMed1998

The validity of the Dutch Sleep Disorders Questionnaire (SDQ).

The Sleep Disorders Questionnaire (SDQ) is a 176-item questionnaire designed to diagnose the presence of common sleep disorders. This study set out to assess the validity of a Dutch translation of the SDQ. Scores on 145 questionnaires were analyzed. A cluster analysis of these scores revealed the following clusters: healthy, depression, insomnia, narcolepsy, and apnea. The cluster classification proved correct for 67% of the subjects, as determined on the basis of polysomnography. These results show that the Dutch SDQ is a reasonably valid instrument for diagnosing sleep disorders.

Adolescent↗
PubMed1998

The prevalence of clinically significant sleep apnoea syndrome in The Netherlands.

BACKGROUND: Figures for the prevalence of sleep apnoea syndrome range from 0.3% to 8.5%. These widely ranged estimates are probably due to differences in the definitions used, study designs, and study populations. A study was undertaken to determine the lower limit of the prevalence of clinically significant sleep apnoea syndrome. METHODS: A cross sectional survey by postal questionnaire was carried out in a general practice of a small town in which three doctors serve 93% of its population of 6747 inhabitants of all ages. All men aged 35 and over and women aged 50 and over were invited to fill in a specially designed questionnaire on snoring and sleep. All men and women whose answers suggested the possible occurrence of sleep apnoea were invited to undergo further investigation. Oronasal thermistry was performed in the subjects' homes and the results were scored to provide an apnoea index (AI). Those subjects with an AI of > or = 5 were referred to a sleep laboratory for investigation by polysomnography. RESULTS: Of the 2466 questionnaires issued, 2182 (88.5%) were completed and returned. The occurrence during the previous three months of regular snoring, together with daytime sleepiness and/or partners' observation of interruptions in breathing at night, was reported by 194 subjects (169 men, 25 women). In 173 subjects oronasal thermistry applied in their homes provided satisfactory recordings and, of these, 24 men and one woman had an AI of > or = 5. Analysis of the polysomnographic findings showed that 14 men and one woman met the criteria for sleep apnoea syndrome. Scrutiny of their case records disclosed that in seven men this was clinically significant. CONCLUSIONS: Our findings suggest that the prevalence of clinically significant sleep apnoea syndrome in men aged 35 and over is at least 0.45%. Extrapolation to the population of the Netherlands suggests that at least 16,000 men suffer from sleep apnoea syndrome that should be relieved by medical care. A large proportion of these subjects remains to be diagnosed.

Adult↗
PubMed1997

Pharmacodynamics of temazepam in primary insomnia: assessment of the value of quantitative electroencephalography and saccadic eye movements in predicting improvement of sleep.

BACKGROUND AND OBJECTIVE: Quantitative electroencephalographic parameters and saccadic eye movements are frequently used as pharmacodynamic measures of benzodiazepine effect. We investigated the relationship between these measures and the hypnotic effect. METHODS: The correlation between the pharmacodynamic measures and sleep quality was determined in 21 patients with primary insomnia. The pharmacokinetic-pharmacodynamic relationships were characterized after administration of 20 mg oral temazepam. The hypnotic effect was determined on the basis of polysomnographic sleep recordings and a subjective sleep evaluation questionnaire. Correlations between pharmacodynamic measures and the improvement of sleep were investigated. RESULTS: The pharmacokinetic-pharmacodynamic relationships for the parameters derived from electroencephalography and saccadic eye movements showed considerable interindividual variability. Administration of temazepam led to a significant improvement in the objective parameters sleep period efficiency, wake time after sleep onset, and sleep efficiency and in the subjective assessment of sleep quality. No significant correlations were observed between the pharmacokinetic-pharmacodynamic-derived parameters and the improvement in objective or subjective sleep parameters. CONCLUSION: In subjects with primary insomnia the administration of 20 mg oral temazepam results in changes in both the pharmacodynamic measures and in quality of sleep. No individual correlations between the pharmacodynamic measures and quality of sleep were observed. We concluded that the investigated pharmacodynamic measures are of value in the first assessment of clinical efficacy and for the selection of the dose(s) to be investigated in subsequent trials that aim at showing clinical efficacy. However, the conclusive quantification of clinical efficacy should be performed only on the basis of the clinical end point itself.

Adult↗
PubMed1996

Subjective sleep characteristics of 1,485 males and females aged 50-93: effects of sex and age, and factors related to self-evaluated quality of sleep.

BACKGROUND: This epidemiologic study cross-sectionally examined the effects of sex and age on subjective characteristics of sleep and the factors related to self-evaluated sleep quality in a Dutch noninstitutionalized elderly population. METHODS: 1,692 sleep questionnaires were mailed to all attenders of the general practice serving Krimpen aan de Lek, The Netherlands, aged 50 or over. Both target population and responders (1,485 subjects) were virtually representative of the Dutch population regarding sex and age (50 +) characteristics. RESULTS: Overall, females reported significantly poorer quality of sleep, longer sleep latencies, more nighttime awakenings, less frequent napping, and more frequent use of sedative-hypnotic drugs when compared to males. Additionally, there was a female predominance in the prevalence of disturbed sleep onset and sleep maintenance, whereas a male predominance was observed in the prevalence of excessive daytime sleepiness. Across subjects, a significant age-related increment was found for sleep latency time and time spent in bed. The number of nighttime awakenings increased significantly with age only in males. No significant correlations were found between health status and sex, age, or subjective sleep quality. The most frequently reported causes of disturbed sleep onset and sleep maintenance were worries and nocturia, respectively. Subjective quality of sleep was mostly associated with self-estimated sleep latency. CONCLUSIONS: Our findings extend those of previous epidemiologic studies reporting that sleep disorders are common in the general elderly population. Future studies should further elucidate the nature and extent of geriatric sleep disorders to satisfy the increasing need for its accurate diagnosis and treatment.

Aged↗
PubMed1995

Age and gender affect different characteristics of slow waves in the sleep EEG.

Low-frequency EEG was analyzed quantitatively during 2 nights in 40 females and 34 males aged 26 to 101 years. Analyses were based on Rechtschaffen and Kales NREM sleep stages, on absolute low-frequency amplitude (i.e. power in the range of 0.2-2.0 Hz) and on low-frequency continuity. The latter parameter describes how much (0-100%) of the current slow-wave activity is continued in the near-future EEG. Such continuation can occur through closed loops in the underlying neuronal network and cells. These loops are slow, thus corresponding to slow-wave frequencies, and can consist of electrophysiological, chemical and/or other pathways. The continuity percentage then monitors the relative activity of these loops. It does not depend directly on absolute EEG amplitudes. All analyzed parameters, including amplitude-independent continuity, decreased substantially and significantly with increasing age. The amplitudes of low-frequency EEG in females were significantly and substantially (40%) larger than those in males. However, the amplitude-independent continuity percentage did not differ between the genders. These findings support the notion that gender-related anatomical differences have a general effect on EEG amplitude, including during slow-wave sleep. Aging, however, specifically affects the neurophysiological slow-wave-generating mechanism.

Adult↗
PubMed1995

Circadian distribution of motor activity and immobility in narcolepsy: assessment with continuous motor activity monitoring.

The circadian distribution of motor activity and immobility of 14 unmedicated narcoleptics and matched controls was evaluated by monitoring continuous wrist motor activity 5 successive days and nights at home. Sleep was also assessed by sleep logs. The amplitude of the circadian rhythm of motor activity and immobility was significantly lower in narcoleptics than in controls. The variables that best distinguish narcoleptics from controls were the diurnal and nocturnal mean duration of uninterrupted immobility, which can be explained by excessive daytime sleepiness and frequent nocturnal awakenings, respectively. Thus, measures of diurnal and nocturnal motor activity and immobility appear useful for the objective assessment of some of the sleep-wakefulness manifestations of narcolepsy.

Adolescent↗
PubMed1995

Wrist actigraphic assessment of sleep in 116 community based subjects suspected of obstructive sleep apnoea syndrome.

BACKGROUND: The combined use of wrist actigraphic assessment and self assessment of sleep in the screening of obstructive sleep apnoea syndrome was evaluated in a community based sample. METHODS: One hundred and sixteen community based subjects clinically suspected of having obstructive sleep apnoea (syndrome) were evaluated by means of simultaneous ambulatory recording of respiration (oronasal flow thermistry), motor activity (wrist actigraphy), and subjective sleep (sleep log) during one night of sleep. RESULTS: The subjects were distributed according to their apnoea index (AI); AI < 1 (non-apnoeic snorers) 44%; AI 1- < 5 39%; and AI > or = 5 17%. High apnoea index values were associated with self reported disturbed sleep initiation and more fragmented and increased levels of motor activity and decreased duration of immobility periods, particularly in those with an apnoea index of > or = 5. Across subjects the duration of immobility periods was the only predictor of the apnoea index, explaining 11% of its variance. Use of the multiple regression equation to discriminate retrospectively between those with an apnoea index of < 1 and > or = 5 resulted in sensitivity and specificity values of 75% and 43%, and 5% and 100%, respectively. CONCLUSIONS: The combined use of a sleep log and actigraphic assessment of sleep failed to identify reliably those subjects who suffered from obstructive sleep apnoea (syndrome) in a sample of community based subjects reporting habitual snoring combined with excessive daytime sleepiness and/or nocturnal respiratory arrests.

Cross-Sectional Studies↗
PubMed1994

Sleep disruption in Parkinson's disease. Assessment by continuous activity monitoring.

OBJECTIVE: To assess differences in activity and immobility during sleep between patients with Parkinson's disease (PD) and healthy subjects and to evaluate the relations of clinical variables with the motor activity measures in patients with PD. DESIGN: Survey, case series. SETTING: University hospital outpatient neurology department and urban population in Leiden, the Netherlands. Motor activity was recorded during 6 successive nights at home with a wrist-worn activity monitor. PARTICIPANTS: Eighty-nine patients with PD and 83 age-matched healthy controls. MAIN OUTCOME MEASURES: For each subject, three mean measures reflecting activity or immobility during the nocturnal period were calculated. RESULTS: Compared with the healthy elderly subjects, patients with PD have an elevated nocturnal activity level and an increased proportion of time with movement, indicating a more disturbed sleep. The mean duration of nocturnal immobility periods was similar for both groups. This measure, however, did reflect the self-reported disturbed sleep maintenance in both groups. The daily dose of levodopa or the use of dopamine agonists in patients not receiving levodopa, rather than disease severity, proved to be the best predictors of nocturnal activity. CONCLUSIONS: We hypothesize that in mildly to moderately affected patients with PD, levodopa or dopamine agonists cause sleep disruption by their effects on sleep regulation. In more severely affected patients, the beneficial effects of these drugs on nocturnal disabilities that cause sleep disruption in PD prevail.

Adult↗
PubMed1994

Sleep and ageing: the effect of institutionalization on subjective and objective characteristics of sleep.

To assess the impact of institutionalization on sleep/wake characteristics of elderly people, we compared subjective (study I: n = 160) and objective (study II: n = 30) sleep/wake measures of non-demented institutionalized subjects and age-matched non-institutionalized controls. We also evaluated the prevalence and causes of various sleep disturbances. The three living conditions, i.e. independently living (IL), service home (SH) and nursing home (NH) were respectively assumed to have minimal, moderate and maximal effects upon the timing, the amount and the quality of the sleep/wake behaviour of the persons involved. Study I showed that a higher level of institutionalization was significantly (p < 0.05) associated with phase-advanced sleep/wake patterns, increased amounts of time spent in bed during the 24-hour period and increased usage of prescribed sedative-hypnotic drugs. Poor sleep quality and disturbed sleep onset occurred significantly mostly in the SH group. No differences between groups were demonstrated with respect to the prevalence of disturbed sleep maintenance, parasomnias and difficulty with awakening and their possible causes, except for environmental noise which was exclusively reported by institutionalized subjects. No differences between groups for any of the objective measures were found (study II). Overall, our findings are in line with previous findings on this topic, although the observed high rate of poor sleep quality and sleep disturbances and their associated causes as observed in institutionalized subjects also occurs in an age-matched non-institutionalized population.

Activities of Daily Living↗
PubMed1993

Ambulatory activity monitoring during sleep: an evaluation of internight and intrasubject variability in healthy persons aged 50-98 years.

The aim of this study was to assess the internight and intrasubject variability of nocturnal activity and immobility measures of 99 healthy subjects aged 50-98 years. Motor activity was recorded at home during 6 successive nights with a wrist-worn activity monitor. The occurrence of suprathreshold motor activity was recorded over 15-second epochs. For each subject, six mean measures reflecting activity or immobility during sleep and their coefficient of variation were calculated. Our results revealed no first-night effect or day-of-week effect of the activity and immobility measures over the 6 nights across all subjects. On the other hand, for all nocturnal activity and immobility measures, a considerable intrasubject variability across the 6 nights was found. Females had a greater intrasubject variability of the mean duration of immobility periods and the movement index than males. The intrasubject variability of all nocturnal activity and immobility measures across the successive age groups remains stable. These findings emphasize that although a first-night effect may be lacking, the intrasubject variability of activity and immobility measures across several nights may still be considerable.

Aged↗
PubMed1993

The origin of excessive daytime sleepiness in the Prader-Willi syndrome.

The polygraphically recorded sleep-wake continuum of 21 Prader-Willi syndrome (PWS) patients was compared with that of 19 normal people. In the Prader-Willi group, excessive daytime sleepiness (EDS) is found in 95% of subjects, and rapid eye movement (REM) sleep disorders occur in 52%. These two features were significantly different from the normal group of subjects. No indications were found for the presence of the apnoea syndrome. The REM sleep disorders are: sleep onset rapid eye movements (SOREM), REM sleep in naps, many arousals during REM sleep, and a significant decrease in total REM sleep. These disturbances in the Prader-Willi group, combined with the presence of EDS and sometimes of cataplexy, are likely to be expressions of a narcoleptic syndrome although this was not sustained by the HLA-DR2 expression above normal. The quality of life of PWS subjects can be improved in some cases by treating them as narcoleptic patients.

Adolescent↗
PubMed1993

Nocturnal activity and immobility across aging (50-98 years) in healthy persons.

OBJECTIVE: To measure the influence of age on measures of nocturnal activity and immobility in 100 healthy subjects aged 50 to 98 years. DESIGN: Cross-sectional study. SETTING: Urban population in Leiden. Recordings were performed at home while the subjects maintained their habitual 24-hour pattern of activities. PARTICIPANTS: 100 subjects without a history of major medical disorders and a normal neurological examination and performance-oriented assessment of gait (Tinetti). MEASUREMENTS: Motor activity was recorded during six successive nights with a wrist-worn activity monitor. The occurrence of supra-threshold motor activity was recorded over 15-second epochs. A questionnaire was used to evaluate sleep habits and the occurrence of sleep disturbances. Four mean measures reflecting activity or immobility during the nocturnal period were calculated for each subject. RESULTS: Only one out of four measures, (ie, the nocturnal proportion of time with movement, increased with age for females. For males, no age effects emerged. The mean duration of nocturnal immobility periods was higher in females than in males. Also, for females, the use of hypnotics increased with successive decades. Sex and the use of hypnotics were significantly related to the mean duration of immobility periods. CONCLUSION: If care is taken not to confound aging with illness, measures of nocturnal activity and immobility reveal only marginal effects of aging.

Activities of Daily Living↗