Morningness-eveningness and daytime functioning in university students: the mediating role of sleep characteristics.

The aim of this study was to explore the mediating role of sleep characteristics in the relationship between morningness-eveningness and three different aspects of daytime functioning: daytime sleepiness, depressive mood and substance use in university students. A multiple mediator model was proposed with sleep debt, poor sleep quality and bedtime delay at weekends as parallel mediators in these relationships. We analysed the data of 1052 university students aged 18-25 years who completed a modified version of the School Sleep Habits Survey, which included questions on sleep and the Composite Scale of Morningness, Sleepiness Scale, Depressive Mood Scale and Substance Use Scale. Students with more pronounced eveningness reported greater daytime sleepiness, greater depressive mood and more frequent substance use, as well as greater sleep debt, poorer sleep quality and greater bedtime delay at weekends. Mediation analyses indicated that morningness-eveningness affected daytime sleepiness and substance use both directly and indirectly through all proposed sleep-related mediators. However, the effect of morningness-eveningness on depressive mood was entirely indirect and was accounted for more by poor sleep than by sleep debt or bedtime irregularity. In conclusion, there are multiple possible mechanisms through which morningness-eveningness affects daytime functioning in university students, and sleep characteristics are a significant mechanism. Sleep debt, poor sleep quality and bedtime irregularity can, to a significant extent, explain the feeling of daytime sleepiness and greater substance use in students with eveningness preferences. However, more depressed mood in the evening-orientated students is primarily a consequence of their poor sleep quality.

Development and the initial validation of a new self-administered questionnaire for an early detection of health status changes in smokers at risk for chronic obstructive pulmonary disease (MARKO questionnaire).

AIM: To develop and do an initial validation of a new simple tool (self-administered questionnaire) that would be sensitive and specific enough to detect early changes in smokers leading to future development of chronic obstructive pulmonary disease (COPD). METHODS: 224 consecutive participants (50.9% women), with mean±standard deviation age of 52.3±6.7 years, 37.5±16.7 pack-years smoking history (85.8% active smokers), and no prior diagnosis of COPD were recruited. The MARKO questionnaire was self-administered twice; at the general practitioner's office and after 2-4 weeks at the tertiary care hospital. Participants were assessed for COPD by a pulmonologist after filling in a quality of life (QoL) questionnaires, history-taking, physical examination, lung function test, 6-minute walk test, and laboratory tests. They were divided into four subgroups: "healthy" smokers, symptomatic smokers, and smokers with mild and moderately severe COPD. RESULTS: Psychometric analyses indicated that the 18-item questionnaire had a very good internal consistency (Cronbach's alpha=0.91) and test-retest reliability for a four week period (c=0.89, 95% confidence interval [CI] 0.85-0.92, Lin's concordance). A significant correlations of MARKO scores were found with two QoL questionnaires; r=0.69 (P<0.001) and r=0.81 (P<0.001). Receiver operating characteristic curve analysis showed an area under the curve of 0.753 (95% CI 0.691-0.808, <0.001), with a sensitivity of 71.83% and specificity of 64.24% to discriminate "healthy" smokers from other subgroups. CONCLUSION: Based on psychometric analyses and high convergent validity correlation with already validated QoL questionnaires, the newly developed MARKO questionnaire was shown to be a reliable self-administered short health status assessment tool.

WHOQOL-bREF questionnaire as a measure of quality of life in sarcoidosis.

The aim of this study was to evaluate the usefulness of a short form of the WHOQOL questionnaire, the WHOQOL-BREF, which consists of 24 questions, in evaluating quality of life (QOL) in sarcoidosis patients. A group of 97 sarcoidosis patients and a matched group of 97 healthy controls took part in the study. Their QOL was examined by means of the WHOQOL-BREF, and the respiratory functions were measured in sarcoidosis patients. The WHOQOL-BREF revealed significantly poorer QOL of sarcoidosis patients in the domains of Physical and Psychological Health in comparison to healthy controls. In contrast, sarcoidosis patients perceived their QOL significantly better than healthy controls in the domains of Social Relations and Environment. Differences between sarcoidosis patients and healthy controls were found in several items from the WHOQOL-BREF and some of them were modified by gender. However, the WHOQOL-BREF did not prove to be a sensitive measure of fatigue, which is the most common symptom in sarcoidosis patients.

Educating adolescents about healthy sleep: experimental study of effectiveness of educational leaflet.

AIM: To evaluate how exposure to educational leaflet about healthy sleep affects knowledge about sleep in adolescents. METHODS: The study included students aged 15-18 years from 12 high schools (1209 participants; 85% of eligible study population). Multistage sampling was used and the selected schools were randomly assigned into two intervention groups and two control groups, according to the Solomon experimental design. Intervention groups received educational leaflets and control groups did not. In one of the intervention groups and one of the control groups, pre-testing of knowledge about sleep was performed. Students answered the Sleep Knowledge Test, which was constructed in accordance with the information on the leaflet. Data were analyzed by four-way ANOVA and additional analyses of simple main effects were performed. RESULTS: Positive effect of educational leaflet was found in students aged 15 (F = 28.46; P < 0.001), 16 (F = 5.74; P = 0.017), and 17 (F = 17.17; P < 0.001), but there was no effect in students aged 18 (P = 0.467). In male students, positive effect of the leaflet was found only in the group that had not been pre-tested (F = 6.29; P = 0.012), while in female students, it was found in both pre-tested (F = 26.24; P < 0.001) and not pre-tested group (F = 17.36; P < 0.001), with greater effect in pre-tested group (F = 5.70; P = 0.017). Female students generally showed better knowledge about sleep than male students (F = 95.95; P < 0.001). CONCLUSION: Educational leaflets can be an effective first step in educating younger high school students about healthy sleep, with the method being more effective in female adolescents.

Association of neuroticism with sick building syndrome, quality of life and psychomotor performance.

In a group of 221 healthy employees of both sexes the relationship between neuroticism, and perceived quality of life (WHOQOL), inadequate work organization (IWO), Sick Building Syndrome (SBS) and speed and accuracy of simple reaction time was studied. The level of neuroticism was assessed by Cornell Index (C.I.), and psychomotor speed and accuracy by electronic psychodiagnostic instrument Complex Reactionmeter Drenovac (CRD). All subjects underwent the same testing procedure completing C.I., SBS, IWO and WHOQOL-BREF questionnaires. The obtained results revealed that persons with more pronounced emotional stability perceive their life better in quality, their work environment with less SBS symptoms, and report more adequate work organization. Furthermore, they have better simple reaction time scores to visual stimuli.

[Individual differences and sleep deprivation effects]. / Individualne razlike i ucinci deprivacije spavanja.

Contemporary lifestyle and different life circumstances often require that individuals restrict their sleep duration and change their sleep schedule. That often leads to sleep deprivation. Former studies showed that sleep deprivation effects on the physiological and psychological functioning of an individual depended on numerous factors such as type of sleep deprivation, previous sleep duration, time of day when the effects were examined, characteristics of tasks performed, and the subject's motivation. This paper discusses the effects of sleep deprivation and the existence of stable individual differences in those effects, named "vulnerability to sleep loss". Recent studies indicate that some characteristics of the subjects could help predict systematic and robust sleep deprivation effects, such as age, sex and personality characteristics. Furthermore, the article discusses the importance of individual differences in specific characteristics related to sleep and wakefulness like those in preferred circadian phase, sleep need, individual level of sleepiness, and the ability to fall asleep quickly. So far, studies of individual characteristics did not result in consistent conclusions about their predictive importance for vulnerability to sleep loss. Further studies directed at this problem could help identify individuals who are more vulnerable to sleep loss, and contribute to personal and public safety of night work.

Circadian components in energy and tension and their relation to physiological activation and performance.

The purpose of the study was to examine validity of R. Thayer's activation model regarding 24h variations of two subjective dimensions of activation (Energy and Tension), and their 24 h relations with indices of physiological activation and performance efficiency. The participants of the study (n = 28 females) spent 26 h under controlled laboratory conditions. Self-ratings of subjective activation and measurements of oral temperature, electrodermal activity, and performance on a visual vigilance task were done every 4 h. Twenty-four-hour variations were examined by means of repeated measures analyses of variance and by group mean cosinor analyses before and after controlling for the data trends. Self-ratings on both dimensions of subjective activation showed significant 24 h variation. Energy showed both nonrhythmic and endogenously determined circadian variation, while 24h variation of tension was dominantly nonrhythmic and most probably determined by exogenous factors. Significant 24 h covariation was found between energy and body temperature. A negative correlation between 24 h variation of energy and tension was also found. Considering low and intermediate levels of subjective activation established over the 24 h in this study, the association of the two dimensions of subjective activation did not prove to be consistent with the assumptions of Thayer's model.

Shiftworking families: parents' working schedule and sleep patterns of adolescents attending school in two shifts.

OBJECTIVE: To explore whether parents' engagement in shift work affects the sleep habits of their adolescent children who attend school in two shifts. METHODS: The data were drawn from an extensive survey of sleep and daytime functioning of adolescents attending school one week in the morning and the other in the afternoon. The participants were 1,386 elementary and high school students (11-18 years old) whose parents were both employed. The data were analyzed using MANOVA, with parents' work schedule, adolescents' gender and type of school as between-subject factors. RESULTS: Parents' working schedule significantly affected the sleep patterns of high school adolescents. When attending school in the morning, adolescents whose parents were both day workers woke up somewhat later than adolescents with one shiftworking parent. In addition, they slept longer than adolescents whose parents were both shift workers. On weekends, adolescents whose parents both worked during the day went to bed earlier than adolescents whose parents were both shiftworkers. They also had smaller bedtime delay on weekends with respect to both morning and afternoon shifts than adolescents for whom one or both parents worked shifts. A significant interaction between parents' working schedule, adolescents' gender and type of school was found for sleep extension on weekends after afternoon shift school. CONCLUSIONS: Parental involvement in shift work has negative effects on the sleep of high school adolescents. It contributes to earlier wake-up time and shorter sleep in a week when adolescents attend school in the morning, as well as to greater bedtime irregularity.

[Stress and allergy]. / Stres i alergija.

Stress is one of the components in the complex interaction of environmental, genetic, physiological, psychological, behavioural and social factors that can influence the body's ability to remain healthy or become healthy, to resist or overcome a disease. Stress can alter neuroendocrine and immune mechanisms of health and disease through various psychosocial processes. In addition, it can affect health through the impact on health-impairing behaviours and on compliance with medical regimens. At the same time, the relationship between stress and health is not unidirectional but bi-directional. Current views on the relation between stress and allergy vary from the denial of any relationship that could fundamentally help in allergy treatment to the widespread opinion that psychological stress can exacerbate some skin symptoms and precipitate asthma. The role of stress in the genesis, incidence and symptomatology of allergy still remains a controversial issue since the mechanisms of that relationship are not well understood. Starting from the biopsychosocial model of disease, we introduced the Social Readjustment Rating Scale which measures stressful life events, and the WHOQOL-BREF which measures subjective quality of life, into an extensive multidisciplinary study of immunotoxic effects of indoor bioaerosols and lifestyle. This paper describes the characteristics of those two questionnaires and discusses the relationship between stress and various domains of the quality of life. The Social Readjustment Rating Scale proved to be a reliable predictor for quality of life in the domains of physical health and environment. Future analyses will examine the role of stress and subjective quality of life in allergy.

Morningness-eveningness and sleep patterns of adolescents attending school in two rotating shifts.

School system in which classes are scheduled 1 week in the morning and the other in the afternoon, and in which students rotate schedule every week, fosters sleep irregularity. In this study, we examined morningness-eveningness of adolescents who were involved in such schedule of school time and explored relationship between their circadian preferences and sleep characteristics. A large sample of 2287 students between the ages 11 and 18 years (52% girls) from 24 schools in Croatia was studied. The School Sleep Habits Survey was modified to enable differentiation of sleep patterns between the two school schedules and weekends. Two measures of ME were used: the Morningness-Eveningness Scale for Children (MESC) and mid-sleep time on weekends (MSFsc). Both measures showed a shift to eveningness starting between the ages 12 and 13 (MESC), or 13 and 14 (MSFsc). However, MESC demonstrated a plateau in the shift in older adolescent whereas MSFsc indicated further progress of phase delay. Significant differences in sleep timing and duration were found between three chronotype groups (Morning, Intermediate, and Evening). Generally, Evening types went to bed and woke up the latest in all situations. Their sleep duration was the shortest on school week with morning schedule. On weekends Morning types slept shorter than other two chronotype groups. On school week with afternoon schedule all chronotype groups slept close to the recommended 9 h. All three chronotype groups delayed their bedtimes and wake-up times, and extended their sleep in situations with fewer constraints on sleep timing (i.e. afternoon school schedule, and weekends versus morning school schedule). Expectedly, the evening types showed the greatest sleep irregularity. The findings of this study suggest that the Croatian school system fosters sleep irregularity, but provides more opportunity for fulfilling sleep need of all chronotype groups of adolescents. Age effects on morningness-eveningness observed in Croatian adolescent do not seem to be different from those observed in adolescents from other countries involved in a regular morning school schedule. Further studies are necessary to explore differences in the trend of shift towards eveningness found between the two measures of morningness-eveningness in this, as well as in other studies.

State-trait arousal and daytime sleepiness after sleep restriction.

The importance of an arousal system in the regulation of sleepiness has been widely recognised in contexts of insomnia theory and research. Arousal is also incorporated in some general models of sleepiness and is considered one of the principal factors regulating sleepiness in a model by De Valck and Cluydts (2003), in which arousal has both state and trait components. In the present experimental study, we explored the effects of state and trait components of arousal on subjective sleepiness and sleep latency during daytime. On a day after partial sleep deprivation, 28 good sleepers aged 18-26 years took part in two successive experimental conditions, in which the state arousal was manipulated by laboratory tasks. We measured physiological (heart rate, frequency of skin conductance responses) and subjective (Energy, Tension, Anxiety) indices of state arousal, while trait arousal was operationalised as electrodermal lability. After a moderately stressful task, which induced a relatively higher state arousal, the participants reported lower sleepiness and took longer to fall asleep than after a simple psychomotor task. Trait arousal was not associated with daytime sleepiness. The results of this study support the idea that short-term changes of state arousal are important for the regulation of sleepiness in good sleepers, even in a situation which is only moderately stressful.

Regulation of sleepiness: the role of the arousal system.

Sleepiness is a widespread phenomenon in the busy industrial countries, and many studies have identified its significant negative impacts on individuals and society. Particularly important are the data that associate sleepiness with the risk of accidents at workplace and in transport, pointing to shift workers as the most vulnerable population. It is generally accepted that two basic physiological processes regulate sleepiness: homeostatic and circadian rhythmic processes. Recent research has proposed the third component regulating sleepiness, that is, the wake drive or the arousal system. The role of the arousal system in regulating sleepiness has partly been addressed by the studies of the pathophysiology of insomnia, which is often described as a disorder of hyperarousal. Experimental and correlational studies on the relation between sleepiness and arousal in good sleepers have generally indicated that both physiological and cognitive arousal are related to the standard measures of sleepiness. Taking into account the role of the arousal system in regulating sleepiness widens the possibilities for the management of sleep disorders and could also help in solving the problem of excessive sleepiness at work and the wheel.

Is atopy related to neuroticism, stress, and subjective quality of life?

Different psychosocial characteristics have been associated with allergic disorders. The aim of this study was to examine whether atopic constitution and reports of allergic symptoms were related to personality trait of neuroticism, exposure to stressful life events and estimates of quality of life. Atopy was determined by skin prick test and reports of nasal and pulmonary allergy-related symptoms. Actively working individuals of both genders took part in the study (n=145, age range: 20 to 66 years). The participants were divided in three groups. The first group was composed of those with negative skin prick test and without symptoms (n=57), the second of those with positive skin prick test but without symptoms (n=28), and the third of those with positive skin prick test and symptoms (n=60). The groups did not differ significantly in neuroticism, exposure to stressful life events, or quality of life. Women reported more pronounced neuroticism and anxiety, higher exposure to stressful life events, and were less satisfied with their environment than men. In our sample of active workers we found no association of neuroticism, exposure to stressful life events, and quality of life with atopy and allergic symptoms.

Sick building syndrome: psychological, somatic, and environmental determinants.

The authors aimed to examine potential relationships between work-related symptoms attributed to sick building syndrome (SBS) and certain psychological, somatic, and environmental factors. The multidisciplinary, cross-sectional study comprised 171 female subjects working in air-conditioned and naturally ventilated nonindustrial office buildings. The authors collected information concerning symptoms related to SBS and made assessments of quality of life by using appropriate questionnaires. They assessed the women's levels of emotional stability or neuroticism using the Cornell Index. They determined skin and airway reactivity markers and indoor microclimate data by using standardized methods. The study showed that the subjects had a high prevalence of fatigue (60.2%), sore and dry eyes (57.9%), and headache (44.4%), as well as a generally high score according to the SBS Index. Neuroticism and subjectively estimated physical health as well as the type of building ventilation significantly contributed to the prediction of the SBS Index, explaining 15% of the variance.

Shiftworking families: parents' working schedule and sleep patterns of adolescents attending school in two shifts

OBJETIVO: Investigar se a ocupação de pais com o trabalho em turnos interfere nos hábitos de sono dos filhos adolescentes que freqüentam a escola em dois períodos distintos. MÉTODOS: Os dados foram coletados em uma extensa pesquisa sobre sono e atividades diurnas de adolescentes que freqüentavam a escola no período da manhã e da tarde em semanas alternadas. Participaram do estudo 1.386 estudantes do ensino fundamental e médio (idades de 11-18 anos) cujos pais trabalhavam fora. Os dados foram analisados usando-se MANOVA, sendo o horário de trabalho dos pais, sexo dos adolescentes e tipo de escola os fatores intra-sujeitos. RESULTADOS: O horário de trabalho dos pais apresentou interferência significativa nos padrões de sono de adolescentes do ensino médio. Quando freqüentavam a escola pela manhã, os adolescentes cujos pais trabalhavam no período diurno levantavam-se um pouco mais tarde do que os adolescentes cujo pai ou mãe trabalhava em turnos. Além disso, eles dormiam mais do que os adolescentes cujos pais trabalhavam em turnos. Nos fins de semana, os adolescentes cujos pais trabalhavam no período diurno iam dormir mais cedo do que os adolescentes cujos pais trabalhavam em turnos. Também apresentaram um atraso menor no horário de dormir nos fins de semana depois da escola tanto no período da manhã quanto da tarde comparados aos adolescentes em que o pai ou a mãe ou ambos trabalhavam em turnos. Verificou-se uma interação significativa entre o horário de trabalho dos pais, sexo dos adolescentes e tipo de escola e a duração do sono nos fins de semana depois da escola no período da tarde. CONCLUSÕES:A ocupação dos pais no trabalho em turnos exerce efeitos negativos no sono de adolescentes do ensino médio, contribuindo para um horário de levantar mais cedo e um período de sono mais curto durante a semana quando os adolescentes freqüentam a escola pela manhã, além de uma maior irregularidade na hora de dormir.