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1.  Delayed sleep phase syndrome in adolescents: prevalence and correlates in a large population based study 
BMC Public Health  2013;13:1163.
The aims of this study were to estimate the prevalence of Delayed Sleep Phase Syndrome (DSPS) in adolescence, and to examine the association to insomnia and school non-attendance.
Data stem from a large population based study in Hordaland County in Norway conducted in 2012, the ung@hordaland study. In all, 10,220 adolescents aged 16–18 years (54% girls) provided self-reported data on a range of sleep parameters: DSPS was defined according to the International Classification of Sleep Disorders, Revised (ICSD-R) criteria, while insomnia was defined according to the Quantitative Criteria for Insomnia. Other sleep parameters included time in bed, sleep duration, sleep efficiency, oversleeping, sleep onset latency, wake after sleep onset, subjective sleep need, sleep deficiency, sleepiness and tiredness. Sleep data were calculated separately for weekdays and weekends. Data on school non-attendance were provided by official registers.
The prevalence of DSPS was 3.3%, and significantly higher among girls (3.7%) than boys (2.7%). There was a strong overlap between DSPS and insomnia, with more than half of the adolescents with DSPS also meeting the criteria for insomnia (53.8% for boys and 57.1% for girls). Adolescents with DSPS had significantly higher odds ratios (OR) of non-attendance at school. After adjusting for sociodeographical factors, insomnia and depression, the adjusted ORs for days of non-attendance were OR = 3.22 (95% CI: 1.94-5.34) for boys and OR = 1.87 (95% CI: 1.25-2.80) for girls. A similar effect was found for hours of non-attendance for boys, with an adjusted OR = 3.05 (95% CI: 1.89-4.92). The effect for girls was no longer significant after full adjustment (OR =1.48 [95% CI: 0.94-2.32]).
This is one of the first studies to estimate the prevalence of DSPS in adolescents. The high prevalence of DSPS, and overlap with insomnia, in combination with the odds of school non-attendance, suggest that a broad and thorough clinical approach is warranted when adolescents present with symptoms of DSPS.
PMCID: PMC3878844  PMID: 24330358
Delayes sleep phase syndrome; Sleep; Prevalence; Correlates; Epidemiology
2.  Personality factors predict sleep-related shift work tolerance in different shifts at 2-year follow-up: a prospective study 
BMJ Open  2013;3(11):e003696.
The aim of the present study was to investigate whether the personality variables morningness, flexibility, languidity and hardiness could predict sleep-related shift work tolerance for the day, evening and night shifts, respectively.
Prospective study design with questionnaires administered in winter 2008/2009 (wave 1) and 2 years later in spring 2011 (wave 3).
Different healthcare institutions in Norway.
The sample comprised in all 700 nurses working a three-shift rotating schedule.
Primary and secondary outcome measures
The personality variables were assessed at wave 1, as were the demographic, lifestyle and work-related variables. Sleep-related shift work tolerance, assessed at wave 3, was measured separately for the day, evening and night shifts with the Bergen Shift Work Sleep Questionnaire.
Morningness was positively associated with sleep-related day shift tolerance (p<0.001). Flexibility was positively associated with sleep-related tolerance for the evening as well as night shift (p<0.001). Furthermore, languidity was negatively associated with sleep-related shift tolerance for the day, evening and night shifts (p<0.001, <0.01, <0.05, respectively). Hardiness was positively associated with sleep-related tolerance for the day, evening and night shifts (p<0.001, <0.01, <0.05, respectively). Age was negatively associated with sleep-related shift tolerance for the day, night (p<0.01) and evening shifts (p<0.001).
The findings indicate that hardiness and languidity predict sleep-related shift work tolerance across all shift types among shift working nurses. The effects of flexibility and morningness seem to depend on the shift schedule. By and large, our results are in accordance with previous studies; however, we have now demonstrated the prospective importance of personality in relation to sleep-related shift work tolerance across different shifts.
PMCID: PMC3822308  PMID: 24189084
Occupational & Industrial Medicine; Sleep Medicine; Mental Health
3.  Insomnia, Excessive Sleepiness, Excessive Fatigue, Anxiety, Depression and Shift Work Disorder in Nurses Having Less than 11 Hours in-Between Shifts 
PLoS ONE  2013;8(8):e70882.
Study objective
To assess if less than 11 hours off work between work shifts (quick returns) was related to insomnia, sleepiness, fatigue, anxiety, depression and shift work disorder among nurses.
A questionnaire including established instruments measuring insomnia (Bergen Insomnia Scale), sleepiness (Epworth Sleepiness Scale), fatigue (Fatigue Questionnaire), anxiety/depression (Hospital Anxiety and Depression Scale) and shift work disorder was administered. Among the 1990 Norwegian nurses who participated in the study; 264 nurses had no quick returns, 724 had 1–30 quick returns and 892 had more than 30 quick returns during the past year. 110 nurses did not report the number of quick returns during the past year. The prevalence of insomnia, excessive sleepiness, excessive fatigue, anxiety, depression and shift work disorder was calculated within the three groups of nurses. Crude and adjusted logistic regression analyses were performed to assess the relation between quick returns and such complaints.
We found a significant positive association between quick returns and insomnia, excessive sleepiness, excessive fatigue and shift work disorder. Anxiety and depression were not related to working quick returns.
There is a health hazard associated with quick returns. Further research should aim to investigate if workplace strategies aimed at reducing the number of quick returns may reduce complaints among workers.
PMCID: PMC3744484  PMID: 23976964
4.  Associations Between Night Work and Anxiety, Depression, Insomnia, Sleepiness and Fatigue in a Sample of Norwegian Nurses 
PLoS ONE  2013;8(8):e70228.
Night work has been reported to be associated with various mental disorders and complaints. We investigated relationships between night work and anxiety, depression, insomnia, sleepiness and fatigue among Norwegian nurses.
The study design was cross-sectional, based on validated self-assessment questionnaires. A total of 5400 nurses were invited to participate in a health survey through the Norwegian Nurses' Organization, whereof 2059 agreed to participate (response rate 38.1%). Nurses completed a questionnaire containing items on demographic variables (gender, age, years of experience as a nurse, marital status and children living at home), work schedule, anxiety/depression (Hospital Anxiety and Depression Scale), insomnia (Bergen Insomnia Scale), sleepiness (Epworth Sleepiness Scale) and fatigue (Fatigue Questionnaire). They were also asked to report number of night shifts in the last 12 months (NNL). First, the parameters were compared between nurses i) never working nights, ii) currently working nights, and iii) previously working nights, using binary logistic regression analyses. Subsequently, a cumulative approach was used investigating associations between NNL with the continuous scores on the same dependent variables in hierarchical multiple regression analyses.
Nurses with current night work were more often categorized with insomnia (OR = 1.48, 95% CI = 1.10–1.99) and chronic fatigue (OR = 1.78, 95% CI = 1.02–3.11) than nurses with no night work experience. Previous night work experience was also associated with insomnia (OR = 1.45, 95% CI = 1.04–2.02). NNL was not associated with any parameters in the regression analyses.
Nurses with current or previous night work reported more insomnia than nurses without any night work experience, and current night work was also associated with chronic fatigue. Anxiety, depression and sleepiness were not associated with night work, and no cumulative effect of night shifts during the last 12 months was found on any parameters.
PMCID: PMC3737208  PMID: 23950914
5.  Early and Later Life Stress Alter Brain Activity and Sleep in Rats 
PLoS ONE  2013;8(7):e69923.
Exposure to early life stress may profoundly influence the developing brain in lasting ways. Neuropsychiatric disorders associated with early life adversity may involve neural changes reflected in EEG power as a measure of brain activity and disturbed sleep. The main aim of the present study was for the first time to characterize possible changes in adult EEG power after postnatal maternal separation in rats. Furthermore, in the same animals, we investigated how EEG power and sleep architecture were affected after exposure to a chronic mild stress protocol. During postnatal day 2–14 male rats were exposed to either long maternal separation (180 min) or brief maternal separation (10 min). Long maternally separated offspring showed a sleep-wake nonspecific reduction in adult EEG power at the frontal EEG derivation compared to the brief maternally separated group. The quality of slow wave sleep differed as the long maternally separated group showed lower delta power in the frontal-frontal EEG and a slower reduction of the sleep pressure. Exposure to chronic mild stress led to a lower EEG power in both groups. Chronic exposure to mild stressors affected sleep differently in the two groups of maternal separation. Long maternally separated offspring showed more total sleep time, more episodes of rapid eye movement sleep and higher percentage of non-rapid eye movement episodes ending in rapid eye movement sleep compared to brief maternal separation. Chronic stress affected similarly other sleep parameters and flattened the sleep homeostasis curves in all offspring. The results confirm that early environmental conditions modulate the brain functioning in a long-lasting way.
PMCID: PMC3724678  PMID: 23922857
6.  Shift Work Disorder in a Random Population Sample – Prevalence and Comorbidities 
PLoS ONE  2013;8(1):e55306.
Few studies have investigated the presence of shift work disorder (SWD) in the general community. We addressed many of the limitations in this literature and present new findings. SWD has been treated as an ‘all or none’ construct but we propose the need to consider the ‘severity’ of the disorder. Using random digit dialling, we randomly recruited 1163 participants. Participants completed an extensive battery of scales and questions concerning work, health and individual differences. Three questions based on the criteria from the International Classification for Sleep Disorders were used to categorise participants with SWD (n = 176). In addition, we asked participants whether SWD interfered with aspects of their life and high ratings were used to define severe shift work disorder (SSWD). The prevalence of SWD was 32.1% among night workers and 10.1% in day workers (p<.001). SSWD was present in 9.1% of night workers and 1.3% of day workers (p<.001). Adjusted logistic regression analyses found significant associations between SWD and night work (OR  = 3.35, CI 2.19-5.12), weekly work hours (OR  = 1.02, CI 1.00–1.04), short sleep (≤6 h; OR  = 2.93, CI 1.94–4.41), languidity (OR  = 1.11, CI 1.06–1.16) and resilience (OR  = 0.56, CI 0.43–0.81). Night work, short sleep, languidity, and hypertension were significantly associated with SSWD. Overall, participants with SSWD slept 0.80 h less than other participants (p<.001). Night work, short sleep and languidity were associated with both SWD and SSWD. Day workers with SWD symptoms reported significantly shorter sleep duration, higher levels of languidity and worked longer working hours compared to day workers without SWD.
PMCID: PMC3555931  PMID: 23372847
7.  NMDA receptor-dependent regulation of miRNA expression and association with Argonaute during LTP in vivo 
microRNAs (miRNAs) are major regulators of protein synthesis in the brain. A major goal is to identify changes in miRNA expression underlying protein synthesis-dependent forms of synaptic plasticity such as long-term potentiation (LTP). Previous analyses focused on changes in miRNA levels in total lysate samples. Here, we asked whether changes in total miRNA accurately reflect changes in the amount of miRNA bound to Argonaute protein within the miRNA-induced silencing complex (miRISC). Ago2 immunoprecipitation was used to isolate RISC-associated miRNAs following high-frequency stimulation (HFS)-induced LTP in the dentate gyrus of anesthetized rats. Using locked-nucleic acid-based PCR cards for high-throughput screening and independent validation by quantitative TaqMan RT-PCR, we identified differential regulation of Ago2-associated and total miRNA expression. The ratio of Ago2/total miRNA expression was regulated bidirectionally in a miRNA-specific manner and was largely dependent on N-methyl-D-aspartate receptor (NMDA) activation during LTP induction. The present results identify miRNA association with Ago2 as a potential control point in activity-dependent synaptic plasticity in the adult brain. Finally, novel computational analysis for targets of the Ago2-associated miRNAs identifies 21 pathways that are enriched and differentially targeted by the miRNAs including axon guidance, mTOR, MAPK, Ras, and LTP.
PMCID: PMC3888942  PMID: 24454279
synaptic plasticity; microRNA; RNA-induced silencing complex; Argonaute; microRNA target prediction; gene expression; protein synthesis; hippocampus
8.  Shift Work Disorder in Nurses – Assessment, Prevalence and Related Health Problems 
PLoS ONE  2012;7(4):e33981.
This study investigates the prevalence of symptoms of shift work disorder in a sample of nurses, and its association to individual, health and work variables.
Methodology/Principal Findings
We investigated three different shift work disorder assessment procedures all based on current diagnostic criteria and employing symptom based questions. Crude and adjusted logistic regression analyses were performed with symptoms of shift work disorder as the dependent variable. Participants (n = 1968) reported age, gender, work schedule, commuting time, weekly work hours, children in household, number of nights and number of shifts separated by less than 11 hours worked the last year, use of bright light therapy, melatonin and sleep medication, and completed the Bergen Insomnia Scale, Epworth Sleepiness Scale, Global Sleep Assessment Questionnaire, Diurnal Scale, Revised Circadian Type Inventory, Dispositional Resilience (Hardiness) Scale – Revised, Fatigue Questionnaire, questions about alcohol and caffeine consumption, as well as the Hospital Anxiety and Depression Scale.
Prevalence rates of symptoms of shift work disorder varied from 32.4–37.6% depending on the assessment method and from 4.8–44.3% depending on the work schedule. Associations were found between symptoms of shift work disorder and age, gender, circadian type, night work, number of shifts separated by less than 11 hours and number of nights worked the last year, insomnia and anxiety. The different assessment procedures yielded similar results (prevalence and logistic regression analyses). The prevalence of symptoms indicative of shift work disorder was high. We argue that three symptom-based questions used in the present study adequately assess shift work disorder in epidemiological studies.
PMCID: PMC3317447  PMID: 22485153
9.  Increased Health Risk in Subjects with High Self-Reported Seasonality 
PLoS ONE  2010;5(3):e9498.
Seasonal variations in mood and behaviour, termed seasonality, are commonly reported in the general population. As a part of a large cross-sectional health survey in Hordaland, Norway, we investigated the relationship between seasonality, objective health measurements and health behaviours.
Methodology/Principal Findings
A total of 11,545 subjects between 40–44 years old participated, completing the Global Seasonality Score, measuring seasonality. Waist/hip circumference, BMI and blood pressure were measured, and blood samples were analyzed for total cholesterol, HDL cholesterol, triglycerides and glucose. Subjects also completed a questionnaire on miscellaneous health behaviours (exercise, smoking, alcohol consumption). Hierarchical linear regression analyses were used to investigate associations between seasonality and objective health measurements, while binary logistic regression was used for analysing associations between seasonality and health behaviours. Analyses were adjusted for sociodemographic factors, month of questionnaire completion and sleep duration. Seasonality was positively associated with high waist-hip-ratio, BMI, triglyceride levels, and in men high total cholesterol. Seasonality was negatively associated with HDL cholesterol. In women seasonality was negatively associated with prevalence of exercise and positively associated with daily cigarette smoking.
High seasonality was associated with objective health risk factors and in women also with health behaviours associated with an increased risk for cardiovascular disease.
PMCID: PMC2831056  PMID: 20209129
10.  A Televised, Web-Based Randomised Trial of an Herbal Remedy (Valerian) for Insomnia 
PLoS ONE  2007;2(10):e1040.
This trial was conducted as part of a project that aims to enhance public understanding and use of research in decisions about healthcare by enabling viewers to participate in research and to follow the process, through television reports and on the web. Valerian is an herbal over-the-counter drug that is widely used for insomnia. Systematic reviews have found inconsistent and inconclusive results about its effects.
Participants were recruited through a weekly nationally televised health program in Norway. Enrolment and data collection were over the Internet. 405 participants who were 18 to 75 years old and had insomnia completed a two week diary-keeping run-in period without treatment and were randomised and mailed valerian or placebo tablets for two weeks. All participants and investigators were blind to treatment until after the analysis was completed.
For the primary outcome of a minimally important improvement in self-reported sleep quality (≥0.5 units on a 7 point scale), the difference between the valerian group (29%) and the placebo group (21%) was not statistically significant (difference 7.5%; 95% CI-0.9 to 15.9; p = 0.08). On the global self-assessment question at the end of the treatment period 5.5% (95% CI 0.2 to 10.8) more participants in the valerian group perceived their sleep as better or much better (p = 0.04). There were similar trends favouring the valerian group for night awakenings (difference = 6.0%, 95% CI-0.5 to 12.5) and sleep duration (difference = 7.5%, 95% CI-1.0 to 16.1). There were no serious adverse events and no important or statistically significant differences in minor adverse events.
Based on this and previous studies, valerian appears to be safe, but with modest beneficial effects at most on insomnia compared to placebo. The combined use of television and the Internet in randomised trials offers opportunities to answer questions about the effects of health care interventions and to improve public understanding and use of randomised trials.
Trial Registration ISRCTN72748991
PMCID: PMC2002515  PMID: 17940604
11.  Factors affecting health status in COPD patients with co-morbid anxiety or depression 
Health status questionnaires provide standardized measures of patients’ perceptions of the impact of disease on their daily life and well-being. Factors associated with health status were examined in a sample of 58 outpatients with chronic obstructive pulmonary disease (COPD) and co-morbid anxiety and/or depression. A cross-sectional descriptive study was conducted with the following measures: The St. George’s Respiratory Questionnaire (SGRQ); the Beck Anxiety Inventory (BAI); the Beck Depression Inventory, 2nd edition (BDI); the Pittsburgh Sleep Quality Index (PSQI); and spirometry. Disease severity as measured with spirometry was not related to health status. Perceptions of poor health as implied by the health status scores were positively associated with symptoms of anxiety and depression, sleep disturbances, and level of daily functioning. There were statistically significant differences between men and women on COPD severity, age, and the BAI scores. The findings emphasize the importance of screening the patients at all stages of disease severity for anxiety, depression, and sleeping problems, in order to provide adequate care for these problems.
PMCID: PMC2695194  PMID: 18229570
COPD; health status; health-related quality of life; anxiety; depression; sleep
12.  Comparing Physical Exercise in Groups to Group Cognitive Behaviour Therapy for the Treatment of Panic Disorder in a Randomized Controlled Trial 
Background: Previous studies have suggested that physical exercise can reduce symptoms for subjects suffering from panic disorder (PD). The efficacy of this intervention has so far not been compared to an established psychotherapy, such as cognitive behaviour therapy (CBT). Assessment of controlled long-term effects and the clinical significance of the treatment are also lacking. Aim: To compare physical exercise to CBT as treatment for PD, and assess controlled long-term and clinically significant effects. Method: PD-patients were randomized to either three weekly sessions of physical exercise (n = 17), or one weekly session of CBT (n = 19). Both treatments ran for 12 weeks, were manualized and administered in groups. Patients were assessed twice before the start of treatment, at post-treatment and at 6 and 12 months thereafter. Primary outcome-measures consisted of the Mobility Inventory (MI), the Agoraphobia Cognitions Questionnaire (ACQ) and the Body Sensations Questionnaire (BSQ). Results: A two-way repeated measures MANOVA of these measures demonstrated a significant effect of time, F(16, 544) = 7.28, p < .01, as well as a significant interaction effect, F(16, 544) = 1.71, p < .05, in favour of CBT. This finding was supported by the assessment of clinically significant changes of avoidant behaviour and of treatment-seeking one year later. Conclusion: Group CBT is more effective than group physical exercise as treatment of panic disorder, both immediately following treatment and at follow-up assessments.
PMCID: PMC3675676  PMID: 22874661
Exercise; cognitive behaviour therapy; panic disorder; anxiety

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