Adolescents' sleep in low-stress and high-stress (exam) times: a prospective quasi-experiment.

This prospective quasi-experiment (N = 175; mean age = 15.14 years) investigates changes in adolescents' sleep from low-stress (regular school week) to high-stress times (exam week), and examines the (moderating) role of chronic sleep reduction, baseline stress, and gender. Sleep was monitored over three consecutive weeks using actigraphy. Adolescents' sleep was more fragmented during the high-stress time than during the low-stress time, meaning that individuals slept more restless during stressful times. However, sleep efficiency, total sleep time, and sleep onset latency remained stable throughout the three consecutive weeks. High chronic sleep reduction was related to later bedtimes, later sleep start times, later sleep end times, later getting up times, and more time spent in bed. Furthermore, low chronic sleep reduction and high baseline stress levels were related to more fragmented sleep during stressful times. This study shows that stressful times can have negative effects on adolescents' sleep fragmentation, especially for adolescents with low chronic sleep reduction or high baseline stress levels.

The Holland Sleep Disorders Questionnaire: Factorial structure and measurement invariance in a psychiatric sample relative to the general population.

OBJECTIVES: Although common, sleep disorders often remain undiagnosed in psychiatric patients. A screening instrument, like the Holland Sleep Disorders Questionnaire (HSDQ) could improve this. Previous work indicated a 6-factor structure for the HSDQ, but this hasn't been investigated in psychiatric patients. METHODS: HSDQ data was collected in a psychiatric-outpatient sample (n = 1082) and general-population sample (n = 2089). Internal reliability of the HSDQ was investigated and Confirmatory Factor Analyses (CFA) were used to compare 1-, 6-, and second-order 6-factor models in both samples. Next, multigroup-CFA was used to investigate measurement invariance. RESULTS: Except for one subscale, internal reliability was acceptable in both samples. The 6-factor structure model fitted best in both samples and investigation of measurement invariance showed evidence for equality of the overall factor structure (configural invariance). Addition of equality constraints on factor loadings (metric invariance) and item thresholds (scalar invariance) showed good fit for all fit statistics, except for one. Exploratory analyses identified three items for metric and three different items for scalar invariance explaining this non-invariance. CONCLUSION: The HSDQ has a 6-factor structure in psychiatric patients, which is comparable to the general population. However, due to the observed non-invariance, users should be cautious with comparing HSDQ scores between psychiatric and general populations.

Holland Sleep Disorders Questionnaire: a new sleep disorders questionnaire based on the International Classification of Sleep Disorders-2.

The primary objectives of this study were to construct a self-assessment questionnaire for sleep disorders based on the International Classification of Sleep Disorders-2, and to evaluate the questionnaire's psychometric properties with respect to its total score and the individual scores for each of the six sleep disorders. In total, 1269 patients, clinically diagnosed with a sleep disorder, and 412 subjects without sleep complaints were enrolled into this study. Principal components analysis confirmed that the Holland Sleep Disorders Questionnaire differentially represented the six symptom clusters associated with International Classification of Sleep Disorders-2 classifications. The Holland Sleep Disorders Questionnaire's total score distinguished patients with a clinically diagnosed sleep disorder from individuals without sleep complaints, with area under the receiver operating curve P(A) of 0.95. The internal reliability coefficient alpha was 0.90 and, applying the Youden criterion as cutoff score, the overall accuracy was 88% (κ: 0.75). Subsequently, the six diagnostic groups of sleep-disordered patients could be differentiated reliably, with P(A) values ranging between 0.69 and 0.95, alpha coefficients ranging between 0.73 and 0.81 and an overall percentage of 85% correctly classified patients (κ = 0.80), indicating a substantial to excellent agreement between the primary diagnoses and the Holland Sleep Disorders Questionnaire classifications.

Prevalence of Sleep Disorders, Risk Factors and Sleep Treatment Needs of Adolescents and Young Adult Childhood Cancer Patients in Follow-Up after Treatment.

BACKGROUND: Sleep disorders negatively impact adolescent and young adult childhood cancer patients' physical and psychosocial health. Early recognition improves timely treatment. We therefore studied the prevalence of subjective sleep disorders, risk factors and sleep treatment needs after completion of childhood cancer treatment. METHODS: Childhood cancer patients (12-26 years old), ≥6 months after treatment, were invited to fill out the Holland Sleep Disorders Questionnaire, which distinguishes six sleep disorders in substantial agreement with the International Classification of Sleep Disorders, second edition (ICSD-2). They additionally indicated sleep treatment needs. Prevalence rates and needs were displayed in percentages. Logistic regression models were used for risk factors. RESULTS: 576 patients participated (response rate 55.8%)-49.5% females, mean age 17.0 years, 44.4% hemato-oncology, 31.9% solid tumors, 23.6% neuro-oncology. Prevalence rates were: insomnia (9.6%), circadian rhythm sleep disorder (CRSD; 8.1%), restless legs syndrome (7.6%), parasomnia (3.5%), hypersomnia (3.5%) and sleep-related breathing disorders (1.8%). Female sex, comorbid health conditions and young adulthood seem to be risk factors for sleep disorders, but cancer-related factors were not. Differing per sleep disorder, 42-72% wanted help, but only 0-5.6% received sleep treatment. CONCLUSIONS: Insomnia and CRSD were most prevalent. An unmet need for sleep treatment was reported by childhood cancer patients during follow-up. Screening for sleep disorders after cancer might improve access to treatment and patient wellbeing.

Effects of nocturnal hemodialysis on melatonin rhythm and sleep-wake behavior: an uncontrolled trial.

BACKGROUND: End-stage renal disease and its treatment are associated with sleep disturbances such as deterioration of the circadian sleep-wake pattern. Melatonin rhythm, which has an important role in this pattern, is disturbed. The nocturnal melatonin surge is absent in this population. Whether nocturnal in-center hemodialysis changes melatonin and sleep-wake rhythms is unknown. STUDY DESIGN: A nonrandomized uncontrolled trial. Patients served as their own controls. SETTING & PARTICIPANTS: Thirteen daytime hemodialysis patients (median age, 58 years; 5 women) from our hospital receiving conventional daytime hemodialysis 3 times weekly for 3 to 4 hours each session. INTERVENTIONS: Six months of treatment with nocturnal in-center dialysis 4 nights/wk with 8-hour sessions. OUTCOMES & MEASUREMENTS: At baseline, while still on conventional hemodialysis therapy, polysomnography was performed, sleep questionnaires were filled out, and melatonin concentration in saliva was obtained. After 6 months of in-center nocturnal hemodialysis, all measurements were repeated. RESULTS: After 6 months of in-center nocturnal hemodialysis, polysomnography showed significant improvements in sleep efficiency (P = 0.05) and stage 3/4 sleep (P = 0.03) in comparison to t = 0. Trends in improvement of rapid-eye-movement sleep, awake time, and oxygen saturation were seen after 6 months of in-center nocturnal hemodialysis therapy. Sleep questionnaires showed a trend in improved sleep quality and daytime function. Patients were less exhausted during the daytime. The nocturnal melatonin surge was partially restored. LIMITATIONS: Small sample size and a nonrandomized uncontrolled study design. CONCLUSIONS: Patients after 6 months of in-center nocturnal hemodialysis had significant improvements in subjective and objective sleep parameters and partially restored nocturnal melatonin rhythm.

The effects of melatonin on sleep-wake rhythm of daytime haemodialysis patients: a randomized, placebo-controlled, cross-over study (EMSCAP study).

AIM: The aim of this study was to investigate the effects of exogenous melatonin on sleep-wake rhythm in haemodialysis patients. METHODS: The study design is a randomized, double-blind, placebo-controlled, cross-over study of 3 x 6 weeks melatonin 3 mg at 22.00 h every night. Haemodialysis patients were asked to fill out a sleep questionnaire and to wear an actometer to record their sleep problems objectively. Furthermore, melatonin concentrations in saliva were sampled the night after daytime haemodialysis and the consecutive night. Actometers, the sleep questionnaire and melatonin concentrations were repeated during the study. RESULTS: In total, 20 patients (six female, median age 71 years) completed the investigation. On nights after daytime dialysis, objective sleep onset latency decreased significantly from a median of 44.5 (placebo) to a median of 15.5 min with melatonin (P < 0.01). Sleep efficiency increased from 67.3 to 73.1% with melatonin (P < 0.05). Actual sleep time increased from 376 min (placebo) to 388 min with melatonin (P < 0.01), and sleep fragmentation decreased from 4.5 to 3.1 (P < 0.01). Furthermore, subjective sleep parameters improved also. Patients reported less time needed to fall asleep (P < 0.05) and fewer wake periods (P < 0.05) on the nights with and without daytime dialysis and an increase in sleep time on the night of daytime dialysis (P < 0.05). Furthermore, the nocturnal melatonin rise was recovered. CONCLUSION: Treatment with melatonin resulted in an improvement of subjective and objective sleep parameters, as well as a recovered nocturnal melatonin rhythm.

Shift work and sleep disorder comorbidity tend to go hand in hand.

Taking into consideration that shift work has a wide-ranging impact on circadian and sleep functioning, it seems likely that shift work increases the risk of a general sleep disturbance, spread out over a multitude of comorbid sleep disorders. The aim of the present study is to analyze and present the sleep disorder data of 250 shift workers and 971 permanent day workers, taken from a nationally representative sample. Additional data concerning duration, timing, and quality of sleep, daytime functioning and social/family variables were added to the analyses. The results showed that the shift workers experienced significantly more difficulties with the variability of their sleep times, reported more napping and considered themselves more as poor sleepers than the day workers. Most importantly, shift work, in comparison with day work, appeared associated with a significantly higher prevalence of the clinical, International Classification of Sleep Disorders' defined symptoms of nearly all main sleep disorders (including shift work disorder). For shift workers, the prevalence of a general sleep disturbance was 39.0% (95%CI 33.2 - 45.2), significantly higher than for day workers (24.6%, 95%CI 22.0 - 27.4). Moreover, shift workers were characterized by high levels of sleep disorder comorbidity. In addition, exclusively for shift workers, the prevalence of disordered sleep systematically decreased across decades of life and was considerably higher for single versus partnered shift workers. This study adds to the insight into the interacting factors that determine shift work coping and may play a role in occupational health interventions aimed at reducing sleep problems and thus improving the resilience and tolerance of the shift worker.

The role of stabilizing and communicating symptoms given overlapping communities in psychopathology networks.

Network theory, as a theoretical and methodological framework, is energizing many research fields, among which clinical psychology and psychiatry. Fundamental to the network theory of psychopathology is the role of specific symptoms and their interactions. Current statistical tools, however, fail to fully capture this constitutional property. We propose community detection tools as a means to evaluate the complex network structure of psychopathology, free from its original boundaries of distinct disorders. Unique to this approach is that symptoms can belong to multiple communities. Using a large community sample and spanning a broad range of symptoms (Symptom Checklist-90-Revised), we identified 18 communities of interconnected symptoms. The differential role of symptoms within and between communities offers a framework to study the clinical concepts of comorbidity, heterogeneity and hallmark symptoms. Symptoms with many and strong connections within a community, defined as stabilizing symptoms, could be thought of as the core of a community, whereas symptoms that belong to multiple communities, defined as communicating symptoms, facilitate the communication between problem areas. We propose that defining symptoms on their stabilizing and/or communicating role within and across communities accelerates our understanding of these clinical phenomena, central to research and treatment of psychopathology.

Epidemiology of sleep and sleep disorders in The Netherlands.

OBJECTIVE: There is a surging public interest in The Netherlands concerning sleep, sleep disorders and associated health. For a proper perspective, it is necessary to have reliable information on the prevalence of sleep characteristics at the national level. This study set out to assess prevalence rates and key characteristics of sleep and sleep disorders in The Netherlands. METHODS: In 2012, a nationally representative sample of 2089 individuals, aged 18-70 years, responded to a set of 48 questions, including the Holland Sleep Disorders Questionnaire, a validated questionnaire based on the International Classification of Sleep Disorders. RESULTS: Prevalence rates were: 32.1% for a general sleep disturbance (GSD), 43.2% for insufficient sleep, 8.2 for insomnia, 5.3% for circadian rhythm sleep disorder, 6.1% for parasomnia, 5.9% for hypersomnolence, 12.5% for restless legs disorder and limb movements during sleep, 7.1% for sleep related breathing disorder, and 12.2% for the presence of comorbidity, ie, the presence of two or more concurrent sleep disorders. In addition, sleep onset time as well as sleep duration showed U-shaped relationships with GSD prevalence rates, with respectively the 22:00-24:00 period and seven to 8 h as optimal associates. CONCLUSIONS: Sleep disorders and insufficient sleep have a high prevalence. As matter of concern, female adolescents reached the highest prevalence rates for most sleep disorders, insufficient sleep and daytime malfunctioning.

Vital working hour schemes: The dynamic balance between various interests.

"Balancing Interests", the theme of the 17th International Symposium on Shift Work and Working Time held in Hoofddorp, The Netherlands (September 2005), refers to the ambition to reach an optimal balance between the various aspects of shift work. Economic, ergonomic, physical, and psychosocial factors all interact in determining the impact of shift work at the individual, organizational, and societal level. It is the challenge of this multidisciplinary field of research to model all relevant factors in such a way that it will allow us to optimize the dynamic trade-off between the yield and the risk of shift work. The organizers of the 17th International Symposium and the co-editors of these proceedings are convinced that the high quality of the contributions will bring us closer to this ultimate goal.

Are individuals' nighttime sleep characteristics prior to shift-work exposure predictive for parameters of daytime sleep after commencing shift work?

This study aimed to examine prospectively whether individual nighttime sleep characteristics at baseline (prior to shift-work exposure) are related to parameters of daytime sleep after commencing shift work. A longitudinal field study was carried out with novice police officers of the Dutch Police Force. A total of 26 subjects were examined at baseline before they entered shift work and re-examined during follow-up sessions after four and twelve months of shift-work exposure. Wrist actigraphy and sleep diaries were used to study nocturnal sleep at baseline and daytime sleep after night shifts during follow-up sessions. As outcome variables, estimated total sleep time, sleep efficiency, and subjective sleep quality were analyzed. Daytime total sleep time showed a 66 min decline during the first year of shift-work exposure. Systematic inter-individual differences were observed for daytime total sleep time and subjective sleep quality (explaining 53% and 38% of the variance, respectively), suggesting potential predictability of these sleep parameters. Although no predictors were found for daytime total sleep time, the subjective quality of nighttime sleep before the onset of shift work predicted 40% of the variance in the subjective quality of daytime sleep after commencing shift work. Follow-up studies may reveal whether the subjective quality of baseline nighttime sleep also predicts long-term overall tolerance for shift work.

Inter-individual differences in sleep response to shift work in novice police officers - A prospective study.

The aim of this longitudinal study on novice police officers was to investigate inter-individual differences in sleep response to shift work, and to identify potential baseline predictors thereof. A total of 42 subjects were assessed at baseline, prior to commencing shift work. They were re-assessed during three follow-up sessions within the first 2 years of shift work exposure after approximately 4, 12, and 20 months of rotating shift work. Wrist actigraphy and sleep logs were used to investigate nocturnal sleep at baseline and daytime sleep after night shifts during the follow-up sessions. Actigraphically estimated total sleep time and subjective sleep quality were analyzed as outcome variables, using mixed-effects analysis of variance. Systematic inter-individual differences were observed in the overall response of these outcome variables to shift work. In this sample, flexibility of sleeping habits and gender were found to be predictors of daytime total sleep time in the first 2 years of shift work exposure. Flexibility of sleeping habits and subjective quality of nighttime sleep prior to shift work were found to be predictors of subjective quality of daytime sleep. These results suggest that it may be possible to detect and even predict sleep deficiencies in response to shift work early on, which could be a basis for the development of individualized interventions to improve shift work tolerance.

Physiologic indexes in chronic insomnia during a constant routine: evidence for general hyperarousal?

STUDY OBJECTIVES: It has been hypothesized that general hyperarousal, present during both sleep and wakefulness, may underlie chronic insomnia. The present study explored, under strictly controlled conditions, whether chronic insomnia is associated with altered physiologic markers of arousal, both in absolute levels and in terms of circadian rhythmicity, relative to controls. DESIGN: A 24-hour constant-routine protocol was implemented to assess physiologic measures. SETTING: The study was conducted in an isolated, temperature- and light-controlled, sound-attenuated sleep laboratory. PARTICIPANTS: Eleven subjects with clinically diagnosed chronic insomnia were compared with 13 healthy matched controls. INTERVENTIONS: The subjects underwent physiologic parameter recordings and cognitive performance testing during 24 hours of total sleep deprivation under strictly controlled circumstances. MEASUREMENTS AND RESULTS: Cardiovascular parameters, free cortisol, and body temperature were subjected to mixed-model analysis of variance and mixed-model harmonic regression. Overall, no differences were found in either the absolute level or the circadian parameters (amplitude, phase) of these variables between the insomniacs and the control subjects. CONCLUSIONS: Although physiologic indexes of arousal were slightly elevated in the insomnia group relative to the controls, the differences between the groups were not statistically significant. This could have been due to a lack of statistical power or could reflect the actual absence of arousal in our sample of chronic insomniacs. Systematic interindividual level differences overwhelmed any differences between the 2 groups, making it unlikely that general hyperarousal was a critical underlying factor in our sample. Earlier findings of hyperarousal in insomnia during studies that allowed sleep may have been specifically related to the sleep state.

Individual differences in the cortisol-awakening response during the first two years of shift work: A longitudinal study in novice police officers.

Cortisol acts as a critical biological intermediary through which chronic stressors like shift work impact upon multiple physiological, neuro-endocrine and hormonal functions. Therefore, the cortisol awakening response (CAR) is suggested as a prime index of shift work tolerance. Repeated assessments of the CAR (calculated as MnInc) in a group of 25 young novice police officers showed that in the interval between about 4 and 14 months after transitioning from regular day work to rotating shift work, mean values began to rise from baseline to significantly higher levels at about 14 months after they commenced shift work. Visual inspection of the individual trends revealed that a subgroup of 10 subjects followed a monotonically rising trend, whereas another 14 subjects, after an initial rise from about 4-14 months, reverted to a smaller, baseline level cortisol response at about 20 months after the start of shift work. If the initial increase in the cortisol response marks the development of a chronic stress response, the subsequent reversal to baseline levels in the subgroup of 14 participants might be indicative of a process of recovery, possibly the development of shift work tolerance.

Melatonin improves health status and sleep in children with idiopathic chronic sleep-onset insomnia: a randomized placebo-controlled trial.

OBJECTIVE: To investigate the effect of melatonin treatment on health status and sleep in children with idiopathic sleep-onset insomnia. METHOD: A randomized, double-blind, placebo-controlled trial was conducted in a Dutch sleep center, involving 62 children, 6 to 12 years of age, who suffered more than 1 year from idiopathic chronic sleep-onset insomnia. Patients received either 5 mg melatonin or placebo at 7 pm. The study consisted of a 1-week baseline period, followed by a 4-week treatment. Health status was measured with the RAND General Health Rating Index (RAND-GHRI) and Functional Status II (FS-II) questionnaires. Lights-off time, sleep onset, and wake-up time were recorded in a diary, and endogenous dim light melatonin onset was measured in saliva. RESULTS: The total scores of the RAND-GHRI and FS-II improved significantly more during melatonin treatment compared to placebo. The magnitude of change was much higher in the melatonin group than in the placebo group, with standardized response means for the RAND-GHRI of 0.69 versus 0.07 and for the FS-II of 1.61 versus 0.64. Melatonin treatment also significantly advanced sleep onset by 57 minutes, sleep offset by 9 minutes, and melatonin onset by 82 minutes, and decreased sleep latency by 17 minutes. Lights-off time and total sleep time did not change. CONCLUSIONS: Melatonin improves health status and advances the sleep-wake rhythm in children with idiopathic chronic sleep-onset insomnia.

24-hour assessment of performance on a palmtop computer: validating a self-constructed test battery.

A test battery was constructed on a palmtop computer for ambulatory purposes. This study explored whether the test battery could assess circadian rhythmicity underconstant routine conditions. Performance, body temperature, and subjective sleepiness of 12 healthy subjects were measured. The test battery consisted of a sleepiness questionnaire and three performance tests: a vigilance detection test, a working memory test, and a choice-reaction time test. The subjects were divided into early-start and late-start groups and were subjected to the constant-routine protocol. All tests showed a trough in performance in the early morning around 07:00h and a peak in the evening between 21:00 and 23:00h. In addition, an afternoon decrement in performance was observed between 15:00 and 17:00h. On average, the circadian (peak-to-trough) variation of the performance variables amounted to 16.9% +/- 1.7 SEM of the maximum across subjects. The late starters showed a larger impairment in performance during the morning than the early starters. This could be attributed to prior wakefulness. The characteristics of the performance rhythms found in this study replicate findings in several other studies carried out under constant routine conditions. In conclusion, the present test battery appeared to be a good tool for future assessment of performance under natural conditions.

Circadian variation in cardiac autonomic activity: reactivity measurements to different types of stressors.

The role of endogenous circadian rhythmicity in autonomic cardiac reactivity to different stressors was investigated. A constant routine protocol was used with repeated exposure to a dual task and a cold pressor test. The 29 subjects were randomly divided into two groups in order to manipulate prior wakefulness. Group 1 started at 09:00 h immediately after a monitored sleep period, whereas group 2 started 12 h later. Measures of interbeat intervals (IBI), respiratory sinus arrythmia (RSA, a measure of parasympathetic activity), pre-ejection period (PEP, a measure of sympathetic activity), as well as core body temperature (CBT) were recorded continuously. Multilevel regression analyses (across-subjects) revealed significant (mainly 24 h) sinusoidal circadian variation in the response to both stressors for IBI and RSA, but not for PEP. Individual 24 + 12 h cosine fits demonstrated a relatively large interindividual variation of the phases of the IBI and RSA rhythms, as compared to that of the CBT rhythm. Sinusoidal by group interactions were found for IBI and PEP, but not for RSA. These findings were interpreted as an indication for endogenous circadian and exogenous parasympathetic (vagal) modulation of cardiac reactivity, while sympathetic reactivity is relatively unaffected by the endogenous circadian drive and mainly influenced by exogenous factors.

Circadian variation in cortisol reactivity to an acute stressor.

To investigate the role of the circadian pacemaker in cortisol reactivity to a cold pressor challenge, 26 diurnally subjects participated in a constant-routine protocol and were divided into two groups. Group 1 started immediately after a monitored sleep period at 09:00 h, while group 2 started 12 h later. After 2 h of adaptation, a cold pressor test was presented every 3 h. The cortisol response was assessed by means of saliva samples that were taken before and after the test. The pretest samples were considered to be base-rate measures and base-rate values as subtracted from post-test values were considered as reactivity measures. Both measures showed distinct Time-of-Day variations (respectively: F(7,168) = 16.92, p < 0.001, epsilon = 0.383; and F(7,175) = 8.01, p < 0.001, epsilon = 0.523). These findings are interpreted as evidence for the existence of an endogenous circadian periodicity underlying the sensitivity of the hypothalamus-pituitary-adrenal (HPA)-axis to acute stress.

Different melatonin rhythms and sleep-wake rhythms in patients on peritoneal dialysis, daytime hemodialysis and nocturnal hemodialysis.

BACKGROUND: Little comparative data on sleep-wake rhythms in different dialysis groups exist. The aim of this study was to investigate sleep-wake parameters measured with actigraphy and sleep questionnaires as well as melatonin rhythms in automated peritoneal dialysis, conventional daytime hemodialysis and nocturnal hemodialysis patients. METHODS: Conventional daytime dialysis (n=20), nocturnal hemodialysis (n=13) and automated peritoneal dialysis patients (n=6) were included in the study. Melatonin in saliva was sampled at 5 time points (21:00, 23:00, 1:00, 7:00 and 9:00 h). Furthermore, actigraphy measurements and sleep questionnaires were performed. All parameters were tested by Kruskall-Wallis test (followed by post hoc Dunn test) to find significant differences (p<0.05). RESULTS: Although most sleep parameters were impaired in all three groups, conventional daytime dialysis patients had the worst sleep. In nocturnal hemodialysis patients a normal nocturnal melatonin rise was found. In daytime hemodialysis and automated peritoneal dialysis patients this rise was absent. CONCLUSIONS: The study showed impaired sleep parameters in all dialysis patient groups. As automated peritoneal dialysis is also performed during night time, the same effect on normalized melatonin was anticipated as was found in nocturnal hemodialysis. Melatonin seems to play a subordinate role in the sleep-wake rhythm of automated peritoneal dialysis patients.