Weekly alternation of morning and afternoon school start times: implications for sleep and daytime functioning of adolescents.

STUDY OBJECTIVES: To examine sleep patterns of adolescents attending school on alternating morning schedule (MS) and afternoon schedule (AS) and to explore the contribution of sleep characteristics on the AS to prediction of adolescents' daytime functioning. METHODS: The Croatian adaptation of the School Sleep Habits Survey for a two-shift school system was completed by 2,033 students (11-18 years old, 54 per cent females) whose school start times alternated weekly between 08:00 am and 14:00 pm. RESULTS: All age groups of adolescents reported delayed sleep when on the school week with an AS as compared with a MS. The average delay of bedtime was 36 minutes, and delay of wake-up time 121 minutes, which resulted in average sleep durations from 9.80 hours in 11-year olds to 8.39 hours in 18-year olds. Having more delayed wake-up times on the AS predicted more substance use and poorer grades. Having more delayed bedtimes not only predicted poorer grades but also predicted less depressed mood. Obtaining relatively longer sleep on AS predicted lower sleepiness, less depressed mood, and less frequent substance use. CONCLUSIONS: The afternoon school start time enables sleep duration that is in line with adolescent sleep biology and contributes positively to daytime functioning. In many cases, a large delay in wake-up time is observed. At least part of that delay is not associated with adolescents' circadian biology and contributes negatively to some indices of their daytime functioning. Further research of factors associated with extreme delays of sleep and/or interventions that could limit extreme sleep irregularity is required.

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.

Skin health and safety at work in Croatian hairdressing apprentices.

BACKGROUND: The risk of developing occupational skin disease (OSD) is high in hairdressers, but may differ between countries. OBJECTIVE: To evaluate safety at work measures, and the prevalence and severity of skin symptoms and their impact on quality of life (QoL), among Croatian hairdressing apprentices. METHODS: Data on self-reported skin symptoms, safety measures and QoL were collected for 101 final-year apprentices. The presence and severity of skin lesions were assessed with the Osnabrueck Hand Eczema Severity Index (OHSI). Transepidermal water loss (TEWL) was measured on the forearm and hand. RESULTS: Ninety-one percent of apprentices reported wearing gloves while dyeing hair, 45% while rinsing hair dyes, and 4% while washing hair. A history of skin symptoms was found in 35% of apprentices, and a history of dry hands in 37%. Skin changes were clinically observed in 40% of apprentices, most frequently erythema, infiltration, and desquamation. The OHSI score ranged from 0 to 6. Only washing hands >20 times per day was positively associated with TEWL. A history of skin symptoms negatively correlated with self-esteem, and social and mental functioning, and positively with anxiety and depression. CONCLUSIONS: The results indicate the need for the continuation of efforts to establish effective primary preventive programmes for OSDs at national and EU levels.

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.

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.

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.

[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.