Shift work is associated with extensively disordered sleep, especially when working nights

Background

Shift work is generally associated with working and sleeping out of phase with the endogenous, circadian sleep-wake cycle. This exerts detrimental effects on sleep health. The present study aimed at evaluating the presence of short and long sleep as well as sleep disorders within a broad range of shift work schedules and elucidating the role of sociodemographic factors therein.

Methods

A large dataset containing information on sleep was collected through advertisement in a Belgium newspaper (De Standaard). Adult, working individuals were selected (n = 37,662) and categorized based on their work schedule (regular day, early morning, evening, night, and rotating shift). In this cross-sectional study, prevalence rates of short sleep (≤6 h), long sleep (≥9 h) and sleep disorders (screened with Holland Sleep Disorders Questionnaire), and associations between these sleep variables and sociodemographics (age, sex, education, living companion(s)) were analyzed using binominal logistic regression analyses.

Results

In the total sample all sociodemographic factors affected prevalences of short, long and disordered sleep, consistent with previous studies. Compared to day workers, shift workers more frequently reported short sleep, most prominently night workers (26 vs. 50%) (p < 0.001). Furthermore, all sleep disorders as well as sleep disorder comorbidity were more common in shift workers, again most pronounced in night workers (all p < 0.05). In night shift workers the level of education had the strongest associations with disturbed sleep with a two-fold higher prevalence of short and disordered sleep in low relative to academic educated groups (all p < 0.02).

Conclusion

Shift work is related not only to curtailed sleep and shift work disorder, but also to a plethora of sleep disorders, including insomnia, sleep-related breathing disorders and sleep-related movement disorders. Our findings imply that education on coping strategies may be especially important for young and/or lower educated shift workers.

[Sleep-wake disorders and DSM-5]

BACKGROUND

Most individuals with mental disorders complain about the problems they experience with sleeping and waking. It is becoming evident that careful diagnosis of sleep-wake disorders is of great importance for the prevention and treatment of mental disorders. Since the introduction of the DSM-IV, clinical scientific research has provided important new insights in this field.

AIM

To find out whether the new classification of sleep-wake disorders in DSM-5 is likely to improve the diagnosis of disorders of this type.

METHOD

We discuss the main changes in the DSM-5 classification of sleep- wake disorders, comparing the new version with the version in DSM-IV.

RESULTS

Because considerable attention is being given to the symptom-orientated and dimensional approach, the classification of sleep-wake disorders in the DSM-5 is closer to current psychiatric practice and it does justice to the current scientific insights into the dimensional nature of psychiatric disorders.

CONCLUSION

The DSM-5 classification takes recent scientific insights into account and might help to improve the diagnosis of sleep-wake disorders in psychiatry.

Virtual reality exposure therapy does not provide any additional value in agoraphobic patients: a randomized controlled trial

BACKGROUND

A number of studies have demonstrated the efficacy of virtual reality exposure therapy (VRET) in specific phobias, but research in seriously impaired patients with agoraphobia is lacking. In this randomized controlled trial with patients with agoraphobia and panic disorder, VRET and exposure in vivo were compared in terms of outcome and processes involved.

METHODS

Patients with panic disorder with agoraphobia (n = 55) were randomly assigned to receive 4 sessions of cognitive behavioral therapy (CBT) followed by either 6 sessions of VRET or 6 sessions of exposure in vivo or to a waiting list control condition.

RESULTS

Analyses showed that both active treatment packages were significantly more effective than no treatment and that no differences between VRET and exposure in vivo were found in three out of four outcome measures. On the panic disorder severity scale, however, CBT plus exposure in vivo was more effective than CBT plus VRET. The results show clear synchrony of temporal processes involved in VRET and exposure in vivo on weekly avoidance measures and cognitive measures. Further, it was shown that initial changes in agoraphobic cognitions during the CBT phase predicted later changes in agoraphobic avoidance behavior.

CONCLUSION

These data support the notion that therapeutic processes involved might be the same in VRET and exposure in vivo. However, given the slight superiority of exposure in vivo above VRET, the costs involved in the implementation of VRET and the lack of long-term follow-up, VRET cannot yet be recommended for patients with agoraphobia.

Age differences in sleep-wake behavior under natural conditions

Differences in lifestyle may account for a considerable portion of the reported age-related changes in overt circadian rhythmicity. By instructing a group of healthy, noninstitutionalized, elderly subjects and a group of young adults to keep a sleep-wake log for a period of two weeks, and to wear an activity monitor for an overlapping period of 11 days, we attempted to assess age-related differences in the habitual sleep-wake behavior, in particular its day-to-day variability. Four clusters of coherent variables were constructed, reflecting (1) circadian phase, (2) variability of sleep-wake behavior, (3) sleep-wake continuity and (4) subjective sleep-wake quality. The results showed that, in comparison with the young subjects, the elderly had a relatively advanced and more regular sleep-wake pattern, reported more midnight awakening and did not differ in their subjective sleep evaluation. In spite of a greater regularity in their lifestyle (which would favor a larger amplitude of the overt circadian rhythmicity) oral temperature measurements showed some evidence of a weakened 24-h periodicity in the elderly.

Genetic analysis of morningness and eveningness

We studied the influence of genetic factors on individual differences in morningness-eveningness in a sample of Dutch twin families. Data were collected from adolescent twins (mean age 17.8 yr) and their parents (mean age of fathers 48.0 yr and of mothers 46.0 yr) and a sample of older twins (mean age 46.5 yr). Scores on morningness-eveningness were rated on a 5-point scale. Parents were more morning oriented than their children, and women were more morning oriented than men. With a twin-family study, separation of genetic and environmental influences on variation in morningness-eveningness is possible. Including parents and older twins in the study makes it possible to explore generation differences in these effects. The correlation between monozygotic twins was more than twice the correlation between dizygotic twins. This indicates that genetic effects may not operate in an additive manner. Therefore, a model that included genetic dominance was explored. Biometrical model fitting showed no sex differences for the magnitude of genetic and environmental factors. The total heritability--the sum of additive and nonadditive genetic influences--for morningness-eveningness was 44% for the younger generation and 47% for the older generation. However, the genetic correlation between the generations turned out to be lower than 0.5, suggesting that different genes for morningness-eveningness are expressed in both generations.

Melatonin for chronic sleep onset insomnia in children: a randomized placebo-controlled trial

To establish the efficacy of melatonin treatment in childhood sleep onset insomnia, 40 elementary school children, 6 to 12 years of age, who suffered more than 1 year from chronic sleep onset insomnia, were studied in a double-blind, placebo-controlled study. The children were randomly assigned to receive either 5-mg melatonin or placebo. The study consisted of a 1-week baseline, consecutively followed by a 4-week treatment period. After that period, treatment was continued if the parents wished so. The study's impact was assessed by measurements of lights-off time, sleep onset, and wake-up time, recorded in a diary (n = 33). Sleep onset was also recorded with an actigraph (n = 25). Endogenous dim light melatonin onset was measured in saliva (n = 27). Sustained attention was evaluated with the Bourdon-Vos reaction time test (n = 36). In the melatonin group, mean (95% CI) lights-off time advanced 34 (6-63) minutes, diary sleep onset 63 (32-94) minutes, actigraphic sleep onset 75 (36-114) minutes, and melatonin onset 57 (24 to 89) minutes; total sleep time increased 41 (19-62) minutes. In the placebo group, these parameters did not shift significantly. The change during the 4-week treatment period differed between the treatment groups significantly as to lights-off time, diary and actigraphic sleep onset, sleep duration, and melatonin onset. There were no significant differences between the treatment groups in the change of sleep latency, wake-up time, and sustained attention reaction times. Mild headache occurred in 2 children during the first 2 days of the melatonin treatment. Eighteen months after the start of the trial, in 13 of the 38 children who could be followed up, melatonin treatment was stopped because their sleep problem was solved and in 1 child because sleep was not improved. Twelve children used melatonin 5 mg, the other 1.0 to 2.5 mg. One child developed mild generalized epilepsy 4 months after the start of the trial. The results show that melatonin, 5 mg at 6 PM, was relatively safe to take in the short term and significantly more effective than placebo in advancing sleep onset and dim light melatonin onset and increasing sleep duration in elementary school children with chronic sleep onset insomnia. Sustained attention was not affected.

Weak 24-h periodicity of body temperature and increased plasma vasopressin in melancholic depression

Earlier work has shown that plasma vasopressin levels of depressed patients were higher than those of healthy controls. The aim of the present study was to determine whether plasma vasopressin levels were correlated to parameters of the circadian rhythm. Forty-one patients with major depression and twenty-five controls participated in a case-control design under natural circumstances in a field study to investigate plasma vasopressin levels three times daily, circadian motor activity, and the 24-h periodicity of body temperature for five consecutive 24-h periods. Temperature measurements consisted of at least five, but mostly six or more measurements every 24 h. Twenty-two percent of the patients, but none of the controls lacked 24-h periodicity of body temperature. In melancholic patients increased vasopressin levels in plasma correlated with a weak 24-h periodicity of body temperature. The role of vasopressin is discussed in the light of the present findings.

Repeated assessment of the endogenous 24-hour profile of blood pressure under constant routine

The impact of environmental and behavioral factors on the 24-h profile of blood pressure (BP) has been well established. Various attempts have been made to control these exogenous factors, in order to investigate a possible endogenous circadian variation of BP. Recently, we reported the results of the first environmentally and behaviorally controlled laboratory study with 24-h recordings of BP and heart rate (HR) during maintained wakefulness. In this constant-routine study, a pronounced endogenous circadian rhythm of HR was found, but circadian variation of BP was absent. This result suggested that the circadian rhythm of BP observed in earlier controlled studies, with sleep allowed, was evoked by the sleep-wake cycle as opposed to the endogenous circadian pacemaker. In order to verify our previous finding during maintained wakefulness, we repeated the experiment five times with six normotensive, healthy young subjects. Statistical analyses of the hourly measurements of BP and HR confirmed the replicable presence of an endogenous circadian rhythm of HR, as well as the consistent absence of an endogenous circadian variation of BP. Thus, this study provided additional evidence that the 24-h profile of BP--as observed under normal circumstances--is the sole result of environmental and behavioral factors such as the occurrence of sleep, and has no endogenous circadian component.

Effects of melatonin on the quality of life in patients with delayed sleep phase syndrome

OBJECTIVE

The purpose of this study was to compare health-related quality of life of delayed sleep phase syndrome (DSPS) patients with a random Dutch sample and four samples of patients with other chronic conditions. We also investigated the effectiveness of treatment with 5 mg of melatonin on the quality of life of DSPS patients.

METHODS

Forty-three DSPS patients completed a quality-of-life questionnaire (Medical Outcome Study Short Form-36 [MOS SF-36] health survey) just before and 2-9 months after participation in a clinical trial involving the administration of melatonin. Scores were compared with responses to the same survey by a random Dutch sample and by patients with sleep apnea, clinical depression, migraine, and osteoarthritis.

RESULTS

MOS SF-36 scales scores were significantly lower in DSPS patients relative to age- and gender-adjusted norms for the Dutch sample. Some health dimensions were more affected, and others less affected, by DSPS compared with the other chronic conditions. Melatonin treatment improved all scales except the scale "role due to emotional problems."

CONCLUSION

DSPS has a unique significant quality-of-life burden that seems to be improved by treatment with melatonin.

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.

Absence of seasonal variation in the phase of the endogenous circadian rhythm in humans

Humans may be subject to seasonal variations, as evidenced by the existence of seasonal affective disorder (SAD) and midwinter insomnia. However, some recent studies have shown that the seasonal variation in the phase of the circadian rhythm is relatively weak in healthy humans. In the present study, evidence is found that there is no seasonal variation in the phase of the endogenous circadian rhythm at all. Body temperature, cortisol excretion, and subjective alertness of six subjects recorded under constant routine conditions showed no systematic seasonal variation in circadian phases. This finding indicates that secondary zeitgebers blocked or counterbalanced the seasonal variation in the entrainment effect of the natural photoperiod. The human being may live in an environment in which the photoperiod has lost its status of primary zeitgeber.

Delayed sleep phase syndrome: A placebo-controlled cross-over study on the effects of melatonin administered five hours before the individual dim light melatonin onset

In a double-blind placebo-controlled cross-over study, 30 patients with Delayed Sleep Phase Syndrome (DSPS) were included, of whom 25 finished the study. Melatonin 5 mg was administered during two weeks in a double-blind setting and two weeks in an open setting successively or interrupted by two week of placebo. The study's impact was assessed by measurements of the 24-h curves of endogenous melatonin production and rectal temperature (n = 14), polysomnography (n = 22), actigraphy (n = 13), sleep log (n = 22), and subjective sleep quality (n = 25). Mean dim light melatonin onset (DLMO) (+/- SD), before treatment, occurred at 23.17 hours (+/- 138 min). Melatonin was administered five hours before the individual DLMO. After treatment, the onset of the nocturnal melatonin profile was significantly advanced by approximately 1.5 hour. Body temperature trough did not advance significantly. During melatonin use, actigraphy showed a significant advance of sleep onset and polysomnography, a significant decreased sleep latency. Sleep architecture was not influenced. During melatonin treatment patients felt significantly more refreshed in the morning. These results show that analysis of DLMO of patients suffering from DSPS is important both for diagnosis and therapy. These results are discussed in terms of the biochemistry of the pineal.

Melatonin-responsive headache in delayed sleep phase syndrome: preliminary observations

The occurrence of headache and its change after treatment with melatonin 5 mg were studied in 30 patients with delayed sleep phase syndrome. The medication was taken 5 hours before the endogenous nocturnal plasma melatonin concentration had reached 10 pg/mL. Three women (aged 14, 14, and 23 years) suffered from chronic tension-type headache. Their headache disappeared within 2 weeks after the start of treatment with melatonin. One 54-year-old man suffered from disabling migraine attacks without aura, twice a week. After starting melatonin treatment, only three migraine attacks were reported in 12 months. Ever since his 40s, a 60-year-old man complained of cluster headache episodes lasting about 2 months, twice a year. In the year since starting melatonin treatment, only one 5-day cluster episode occurred. Nocturnal melatonin secretion in the patients with delayed sleep phase syndrome and headache did not differ significantly from that in the patients with the sleep disorder but without headache. Melatonin may be helpful in patients with headache who are suffering from delayed sleep phase syndrome. Its effectiveness may be due to modification of vascular and nociceptive systems or to its chronobiological action which adjusts the patient's biological clock to his/her life-style.

Absence of endogenous circadian rhythmicity in blood pressure?

Currently available evidence reveals a predominant role of exogenous (so-called "masking") factors in the 24 h variation of blood pressure in humans. The existence of a (minor) endogenous circadian factor cannot be excluded, however. This possibility was tested by applying the rigorous unmasking conditions of the constant-routine protocol, that is, strict bed rest in a separate bedroom, total sleep deprivation, constant ambient temperature and illumination, and hourly equicaloric food and liquid intake. Twenty-five normotensive young individuals were subjected to a 26 h constant-routine procedure while hourly measurements were made of their blood pressure and heart rate. Repeated-measures analysis of variance failed to show a significant 24 h variation of blood pressure. The power of this test appeared satisfactorily high (>0.95). Heart rate, however, exhibited a significant circadian pattern, with a range of 6.7 beats/min (10% of the 24 h mean value). Moreover, the timing of the 24 h heart rate curves differed significantly between so-called morning (n = 10) and evening (n = 9) individuals. Mean peak values for the morning-types occurred at 11 AM, for the evening types nearly 6 h later. In conclusion, no evidence was found for the involvement of a circadian oscillator in the regulation of blood pressure.

The 24-hour variation of mood differs between morning- and evening-type individuals

This study investigated a 24-hour variation of subjective mood in 16 healthy Morning-type and 13 Evening-type subjects as defined by the time of day at which their oral temperature curve reached its maximum. The subjects were instructed to use a sleep-wake logbook, in which they kept daily records of the ratings of their mood and alertness for a period of two consecutive weeks. For mood as well as for alertness analysis of variance indicated significant interactions between Morning and Evening-types and time of day. It is concluded that a pronounced diurnal variation of mood can be observed in healthy individuals, which differs between Morning-type and Evening-type subjects.

Plasma arginine vasopressin and motor activity in major depression

BACKGROUND

Previously, we found that mean plasma concentrations of arginine vasopressin (AVP), but not of oxytocin (OT), were higher in depressed patients than in healthy controls. Plasma AVP concentrations were positively correlated to clinically rated psychomotor retardation. To further explore this previously reported relation we studied psychomotor retardation by means of an activity monitor, which is a more fine-focused and more objective instrument to analyze motor retardation than a clinical rating scale.

METHODS

Plasma AVP and OT concentrations, and day- and nighttime wrist activity were measured in 48 in- and outpatients with major depression and 30 healthy controls during a period of 5 consecutive days and nights.

RESULTS

Principal components analysis revealed three components of motor activity: motor activity during wakefulness, motor activity during sleep, and the awake/sleep time ratio. In patients and controls an inverse relationship between plasma AVP concentrations and motor activity during wakefulness was found. Patients with elevated AVP plasma levels showed increased motor activity during sleep.

CONCLUSIONS

These results suggest that high plasma AVP levels are related to the clinical picture of daytime psychomotor retardation and nighttime motor activity in major depression. Mean plasma OT concentrations were not related to measures of motor activity.

Traumatic brain injury-associated delayed sleep phase syndrome

A 15-year-old girl developed a prominent delayed sleep phase syndrome (DSPS) following traumatic brain injury. Several physiological markers of the sleep-wake rhythm: plasma melatonin, body temperature, wrist activity and sleep architecture (EEG) were delayed almost half a day, returning to normal after treatment with 5 mg melatonin. This report suggests an association between traumatic brain injury and DSPS. Awareness of this phenomenon may result in better possibilities for treatment of patients with brain injury.

Seasonal covariation of the circadian phases of rectal temperature and slow wave sleep onset

There is a scarcity of well-controlled studies of the seasonal variation in circadian rhythmicity. In the present study, the circadian phase of rectal temperature and the onset of slow wave sleep were studied in a series of twelve 24-h experiments, one each month of the year, for six healthy subjects under controlled conditions in a climatic chamber. In winter, as compared with summer, the average circadian rhythm of rectal temperature was phase delayed by 45 min, and the average onset of slow wave sleep was phase delayed by 40 min. The temporal relationship between the circadian phase of rectal temperature and the timing of slow wave sleep was maintained throughout the year. Habitual rising and retiring times covaried as well. Furthermore, the circadian rhythm of rectal temperature followed the timing of the photoperiod across the year, but had a much smaller range of seasonal variation. Apparently, the seasonal variation in the photoperiodic zeitgeber is largely compensated for by the stabilizing influence of secondary zeitgebers. However, in healthy subjects some effect of photoperiodic variation can still be observed.

Morning-type and evening-type individuals differ in the phase position of their endogenous circadian oscillator

In dealing with inter-individual phase differences in overt circadian rhythms, it is often difficult to distinguish the impact of the endogenous circadian oscillator from that of an individual's habitual lifestyle. In an attempt to resolve this uncertainty about the role of masking influences, two groups of subjects, morning-type and evening-types, were selected and monitored during entrained, habitual sleep-wake conditions and during 24 h of controlled wakefulness in a laboratory-based constant-routine procedure. Under both conditions significant differences were observed in the circadian phases of body temperature and subjective alertness. During constant routine mean between-group differences for these two variables were 2.21 and 4.28 h, respectively. Thus, evidence is provided for the endogenous nature of morningness-eveningness.

Suicidality, circadian activity rhythms and platelet serotonergic measures in patients with recurrent suicidal behaviour

The circadian activity rhythm was assessed over a one-week period using a wrist-worn activity monitor in 59 patients with a history of recurrent suicide attempts. In 40 of these patients a second recording was made 6 months later. Platelet serotonin (5-HT) and monoamine oxidase-B activity (MAO) were measured. Suicidal ideation, borderline personality disorder and impulsiveness were associated with the absence of a clear 24-hour periodicity in motor activity. Depressive mood and hopelessness were associated with a less regular bed-in time and a lower daytime activity. Platelet 5-HT as well as MAO correlated negatively with the amplitude of the circadian activity rhythm. Our results support the suggested link between suicidality, altered circadian activity and serotonergic function.

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.

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.

Sleep, excessive daytime sleepiness and fatigue in Parkinson's disease

The objective of this questionnaire-based survey was to evaluate the prevalence and causes of sleep disturbances in 90 nondepressive patients with Parkinson's disease (PD) and 71 age-matched healthy subjects. We also assessed the prevalence and characteristics of excessive daytime sleepiness (both groups) and excessive fatigue (PD patients). A high prevalence of sleep disturbances in PD patients was found; this is to a large extent probably the result of aging. As compared with controls, patients had a more severely disturbed sleep maintenance because of nycturia, pain, stiffness, and problems with turning in bed. The prevalence of excessive dreaming is similar in both groups, but altered dream experiences almost exclusively occurred in PD. Patients rated themselves more often to be morning-types than controls. This finding may account for the reported adaptation effects in experimental settings and the reduced REM latency in PD patients. The prevalence of daytime sleepiness was similar in both groups. Excessive daytime sleepiness showed a clear diurnal pattern with a peak in the early afternoon. As for excessive fatigue, the majority of the patients did not report a preferential time for this symptom. Our findings further argue against an association of fatigue with any circadian factor, and instead suggest a relationship with the motor deficits of PD.

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.

Diurnal effects of motor activity and fatigue in Parkinson's disease

Wrist motor activity was monitored continuously in 65 patients with Parkinson's disease (PD) to assess the influence of disease severity and excessive fatigue on the diurnal motor activity pattern. Mildly or moderately affected PD patients had a similar diurnal pattern to that of 68 healthy controls, with a late morning peak; however, mean levels of motor activity were lower. The most severely affected patients showed an overall flattened diurnal pattern. Results refute the existence of end of day deterioration, but instead suggest a "depressed morning start" in the most severely affected patients with PD. Excessive fatigue was not reported at a particular time of day and did not influence the diurnal motor activity pattern.

Assessment of response fluctuations in Parkinson's disease by ambulatory wrist activity monitoring

The aim of this study was to examine the influence of response fluctuations with dyskinesia on the 24-h motor activity pattern and measures of diurnal and nocturnal activity and immobility. Motor activity was recorded during 5 successive days in 5 patients with advanced Parkinson's disease (PD) suffering from severe response fluctuations with dyskinesia, as well as in 10 PD patients with a stable levodopa response and 10 healthy subjects. The 24-h motor activity pattern of the patients with response fluctuations provides insight into the relationship between the therapeutic regimen and 1) the frequency and duration of "on" and "off" periods, 2) the severity of the dyskinesias, and 3) the degree of sleep disruption. In accordance with the severity of their motor fluctuations, patients with response fluctuations showed a large intra- and interindividual variability of diurnal motor activity measures. Overall, the nocturnal motor activity measures in the patients with response fluctuations indicated a severely disturbed sleep when compared with the two control groups. Factors as simplicity and the potential to record unrestrained motor activity for several days continuously in all settings, make activity monitoring a welcomed acquisition in the assessment of response fluctuations in PD.

Quantitative assessment of parkinsonian patients by continuous wrist activity monitoring

The aim of this study was to examine the quantitative relationship between activity monitor measures and clinical scores of patients with Parkinson disease (PD). Motor activity was recorded continuously for 5 to 6 days at home with a wrist-worn activity monitor in 69 PD patients and 59 healthy controls. Clinical scores of the patients, age, and sex were submitted to multiple regression analysis to examine the quantitative relationship with measures reflecting the activity level and the proportion of activity and immobility over time. The patients' age, sex, and scores representing hypokinesia and rigidity and resting tremor explained approximately 50% of the variance of the motor activity measures. All motor activity measures declined with age; the rate of decline was similar for the patients and controls. Sex emerged as a predictor of the motor activity measures in the patients only. Male patients with PD showed significantly lower values for all motor activity measures than female patients and controls. Our results show that activity monitoring can be used as an objective quantitative assessment in PD.

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.

Disruption of sleep-wake rhythmicity and daytime sleepiness in myotonic dystrophy

Ten patients with myotonic dystrophy (MyD) and excessive daytime sleepiness (EDS) were studied. Daytime sleepiness was assessed by means of a subjective alertness rating scale, multiple sleep latency tests and auditory event-related potentials. In addition, the diurnal pattern of daytime sleepiness and ultradian rhythm characteristics of nocturnal sleep were assessed. The multiple sleep latency tests and the P300 component of the auditory event-related potentials gave evidence of EDS, whereas the subjective alertness ratings did not. However, the alertness ratings showed a significantly reduced circadian periodicity as compared with controls. Consistent with this, no time-of-day effect was observed for the multiple sleep latency test outcomes. The ultradian rhythm characteristics of nocturnal sleep indicated a prolonged mean cycle duration and decreased stability of NREM/REM cycle. Moreover, the temporal structure of REM sleep showed a pattern similar to that of subjects who develop free-running rhythms when living in temporal isolation. These findings suggest that EDS in MyD reflects a complex and wide-spread malfunction of the circadian and ultradian timing system.

EEG slow wave activity, REM sleep, and rectal temperature during night and day sleep in morning-type and evening-type subjects

During 3 baseline nights (2 for adaptation) and during 3 days of a sleep-wake reversal, electrophysiological characteristics of sleep and rectal temperature were recorded in 8 morning-type (M-type) and 8 evening-type (E-type) subjects, living in a quiet sleep laboratory. Outcomes of visual sleep scoring revealed the following general tendencies for day-sleep as compared to night-sleep: shorter sleep latencies, shorter REM (rapid eye movement sleep) latencies, advance of the time of maximum REM duration, increased duration of slow wave sleep, more intermittent wakefulness, and decreased subjective sleep quality. Furthermore, for the M-types consistently shorter sleep latencies and--for day-sleep--longer REM latencies were observed than those for the E-types. With regard to the parabolic time course of REM duration, M-types appeared to be relatively phase advanced, in particular for their day-sleep. In addition, subjective sleep quality was consistently higher for the M-types, with the exception of the first day-sleep. The temporal distributions of EEG delta (0.5-3.5 Hz) energy over the first four NREM/REM cycles of day-sleep all deviated from a monotonically decreasing trend. Compared to night-sleep the M-types showed a relative increase of delta energy for Cycle 2, whereas for the E-types a relative increase for Cycles 3 and 4 was observed. An analysis of delta energy, employing a pattern-recognition technique independently from visual sleep scoring, revealed an overall faster rate of accumulation for the M-types. Following sleep onset, rectal temperature showed a decrement, which was larger for the M-types. Moreover, rectal temperature and delta energy were negatively related, as indicated by a negative mean intra-individual correlation. These results are discussed in relation to the characteristic sleep-wake behavior of M-types and E-types.

A new approach in the assessment of motor activity in Parkinson's disease

Motor activity was recorded continuously with a wrist-worn activity monitor for almost six days in nine patients with different predominant manifestations of Parkinson's disease and 10 normal subjects. The indices of diurnal motor activity decreased with the progressive worsening of hypokinesia and rigidity. With this monitor and a simple diary it was possible to determine the contribution of a moderate resting tremor and choreiform dyskinesias to the motor activity level, and to monitor their variability.

Sleep structure and EEG power density in morning types and evening types during a simulated day and night shift

The objective of this study was to examine circadian and homeostatic regulation of sleep in humans. In 8 morning types (M-types) and in 8 evening types (E-types), sleep was recorded during 3 successive nights and, after shifting sleep to the daytime, during 3 consecutive days. Night sleep was highly similar in the M-types and E-types. Day sleep clearly differed from night sleep in both types: Day sleep was shorter and had a longer first REMS episode. Furthermore, EEG power density recorded during non-REMS in the delta and theta frequency bands was higher during all day-sleep periods. Remarkably, the enhancements did not occur in non-REMS episode 1 but were delayed. This was interpreted as an inhibition of EEG power density at the beginning of sleep, possibly caused by the time course of body temperature and/or by the higher REMS propensity. Also, clear differences between the types became apparent: Only in the E-types, the non-REMS episodes shortened in response to the shift in bedtime, and probably related to this, the time course of EEG power density over consecutive non-REMS episodes became almost flat. It was concluded that the circadian system exerts not only an influence on sleep duration and REMS propensity, but also affects the time course of the non-REMS process.

Differences between morning-types and evening-types in the dynamics of EEG slow wave activity during night sleep

During baseline nights in a sleep laboratory electrophysiological sleep records were made for 8 morning-type subjects (M-types) and 8 evening-type subjects (E-types). As compared with the E-types, the M-types were relatively advanced with respect to the times of maximum and minimum rectal temperature and sleep times. Also, the M-types showed a larger initial temperature drop after sleep onset. Comparisons of the outcomes of visual sleep scoring revealed for the M-types a shorter sleep latency and a longer sleep duration. In addition, the M-types reported a higher subjective sleep quality than the E-types. For the M-types sleep stages 3 + 4 and EEG delta (0.5-3.5 Hz) energy declined monotonically across the first 4 NREM/REM cycles. For the E-types, however, no decrement was observed over the first 2 cycles. Analysis of the wave forms of delta energy, employing a pattern recognition technique independent of visual sleep scoring, substantiated this finding. These results are discussed in relation to the differences in circadian characteristics between M-types and E-types.

Ambulatory first night sleep effect recording in the elderly

The concept of a first night effect on sleep patterns, specifically in relation to age is a controversial topic in the literature. Our data are obtained during two consecutive 24-h ambulatory home sleep-wake recording in 10 elderly persons with a mean age of 85.5 years. Polysomnographic recordings indicated that a first night effect is present in old age, even using home recording, and that several types of insomnia can be differentiated, stressing that sleep cycle parameters should be taken into account. It is suggested that the first night effect is a 'miniature' replication of a psychophysiological insomnia.

Effects of repeated sleep deprivation in the dark- or light-period on sleep in rats

This study was designed to examine the differences between sleep duration and EEG when sleep was restricted to the rest- or activity-phase for 5 successive days, achieved by repeated sleep deprivation in the dark (DSD) or light-period (LSD). In the DSD-experiment the percentages of the vigilance states were comparable to the level of the baseline light period. In LSD, the amounts of all sleep states increased substantially relative to baseline dark. The sleep episodes were lengthened in DSD and LSD. The duration of NREM-sleep and the sleep episodes remained longer in the light than in the dark, indicating circadian influences. In the first hours after sleep deprivation the delta activity during NREM-sleep was enhanced in LSD and to a lesser extent in DSD. This effect diminished over the consecutive days in both experiments. The EEG energy gained during sleep and its accumulation pattern on each day in DSD and LSD were strikingly similar, thereby reflecting a homeostatic process. After the sleep deprivation days, small changes were observed in the distribution of the vigilance states, the delta activity and EEG energy over the light- and dark-period.

Inter-individual differences in the human circadian system: a review

Measurements of physiological, biochemical and psychological variables at two or more different times of day reveal substantial inter-individual differences. This paper reviews studies which have dealt with these differences in terms of the morningness-eveningness, personality (introversion-extraversion), age or sex of their subjects. Studies of individual differences in the response of the circadian system to disturbance (e.g. shift work) are also discussed. The most reliable differences were observed in association with the morningness-eveningness factor. From the studies reviewed here it appeared that several rhythm parameters covaried consistently as a function of morningness-eveningness, suggesting underlying differences in the intrinsic period of the circadian system. It is argued that the differences in rhythm parameters associated with the personality dimension of introversion-extraversion are the result of exogenous influences. The results with regard to age-related and sex-related differences were not sufficient to allow conclusions to be made.

P3 latency in threshold signal detection

The EOG, EEG(Cz, Pz) and response latencies were obtained from ten subjects in an auditory threshold detection task with a signal probability of 0.5. In order to minimize any interaction of signal condition (signal-presence vs. signal-absence) and uncertainty about the moment of signal occurrence (temporal equivocation), the observation period was marked with a cue light. The single-trial latencies of the P3 component associated with correct signal-present and signal-absent decisions were assessed on the basis of the cross-covariance functions of the EEG epochs and a template of the P3. Trials with values of covariance smaller than a criterion value were discarded. The mean and dispersion of the P3 latency proved larger for signal-absent than for signal-present trials, while the mean values of covariance were smaller for signal-absent than for signal-present trials. In addition, the mean and dispersion of the P3 proved smaller for high confidence than for medium confidence signal-present trials. Nearly all these effects also proved significant for the response latency. The single-trial P3 latencies were positively correlated with the response latencies of the same trials. The observed latency variations of the P3 were interpreted in terms of changes in the detectability of the stimulus events. It was concluded that the signal condition had a significant effect upon the latency of the P3 associated with signal-present and signal-absent decisions over and above that due to temporal equivocation.

Diurnal differences between morning-type and evening-type subjects in self-rated alertness, body temperature and the visual and auditory evoked potential

On the basis of their score on a morningness/eveningness questionnaire 9 extreme morning-type (M-type) and 9 extreme evening-type (E-type) subjects were selected. During a morning and an evening session both groups performed a reaction-time task with a visual and an auditory warning signal. The results showed that (i) M-types have a higher self-rated activation level in the morning than in the evening, while E-types show the reverse; (ii) M-types do not differ in oral temperature between the two sessions, while E-types show an increased temperature in the evening; (iii) M-types have a larger N1-P2 amplitude of the visual and auditory AEP in the morning than in the evening, while E-types show the reverse.