Fernando Mazzilli Louzada

Adolescents Living in Homes Without Electric Lighting Have Earlier Sleep Times

The aim of this project was to compare circadian rhythmicity of a group of 37 adolescents (14 girls), aged 11 to 16 (mean age = 13.1 ± 1.7 years), with and without electricity at home. Twenty students attended morning school (07:30–11:30), and 17 attended evening school classes (19:00–22:30). Eleven adolescents had no electric lighting at home (5 attended morning classes and 6 attended evening classes). They completed a sleep log and wore a wrist actigraph for 5 consecutive days. Saliva samples were collected to assess DLMO. Data were compared by ANOVA and showed later timing and a more extended sleep period for those who attended late classes. Those adolescents without electricity at home had significantly earlier sleep onset on school days. As to DLMO, a trend to a delay was observed in the groups who had electric lighting.

Sleep–Wake Cycle in Rural Populations

The light/dark cycle is the main zeitgeber acting on the mammalian circadian system; nevertheless, distinct environments, such as those with and without electricity may provoke important resetting effects on the clock. The aim of this study was to describe sleep/wake patterns of adolescents living in two Brazilian rural regions. In the first population, 120 adolescents participated in the study, 35 of whom did not have electricity at home. They filled out a questionnaire which included questions concerning their sleep habits. It was found that electricity at home influenced sleep patterns. Adolescents with electricity at home had later wake-up times on school days (p < 0.05) and on weekends (p < 0.05), and tendencies towards later bedtimes on school days (0.05 < p < 0.10) and weekends (0.05 < p < 0.10). In the second population, 461 adolescents filled out the same questionnaire, 66 of whom did not have television at home. ANOVA showed that having TV at home was related to later bedtimes during school days (p < 0.05) and weekends (p < 0.05). These results support the idea that sleep patterns are influenced by technological advances.

Wrist actigraphy for measuring sleep in intervention studies with Alzheimer's disease patients: Application, usefulness, and challenges

Sleep disorders are common in patients with Alzheimers disease (AD). An important aspect of intervention studies in patients with sleep disorders is the choice of assessment strategy. This paper presents a literature review concerning assessment strategies for measuring sleep in intervention studies with AD patients, with a focus on actigraphy. Thirty-seven articles were selected for this review, having analysis of sleep/nocturnal rhythm disturbances by actigraphy as the primary or secondary outcome. The advantages and limitations of actigraphy were discussed vis-à-vis polysomnography and subjective interventions. The following methodological aspects were addressed: impact of experimental design and patient setting, inclusion and exclusion criteria, placement of the actigraphy device, adherence to the regimen, duration of recordings and the choice of sleep parameters. Our analyses suggest that the methods used in intervention studies encompassing sleep disorders and dementia could be improved by increasing accuracy of diagnosis, categorization of sleep disturbances, adherence to actigraphy, and by clearly defining the variables and endpoints in each study. Also, controlling variables that could interfere with sleep and describing the data processing and analysis might improve interpretation of results.

A fresh look at the use of nonparametric analysis in actimetry

Actimetry has been used to estimate the sleep-wake cycle instead of the rest-activity rhythm. Although algorithms for assessing sleep from actimetry data exist, it is useful to analyze the rest-activity rhythm using nonparametric methods. This would then allow rest-activity rhythm stability, fragmentation and amplitude to be quantified. In addition, sleep and wakefulness efficiency can be quantified separately. These variables have been used in studies analyzing the effect of age, diseases and their respective treatments on human circadian rhythmicity. In this study, we carried out a comprehensive analysis of the main results from published articles and devised a functional model of interaction among the several components involved in generating the sleep-wake cycle. The nonparametric variables render it possible to infer the main characteristics of circadian rhythms, such as synchronization with a zeitgeber, and its amplitude and robustness.

After Being Challenged by a Video Game Problem, Sleep Increases the Chance to Solve It

In the past years many studies have demonstrated the role of sleep on memory consolidation. It is known that sleeping after learning a declarative or non-declarative task, is better than remaining awake. Furthermore, there are reports of a possible role for dreams in consolidation of declarative memories. Other studies have reported the effect of naps on memory consolidation. With similar protocols, another set of studies indicated that sleep has a role in creativity and problem-solving. Here we hypothesised that sleep can increase the likelihood of solving problems. After struggling to solve a video game problem, subjects who took a nap (n = 14) were almost twice as likely to solve it when compared to the wake control group (n = 15). It is interesting to note that, in the nap group 9 out 14 subjects engaged in slow-wave sleep (SWS) and all solved the problem. Surprisingly, we did not find a significant involvement of Rapid Eye Movement (REM) sleep in this task. Slow-wave sleep is believed to be crucial for the transfer of memory-related information to the neocortex and implement intentions. Sleep can benefit problem-solving through the generalisation of newly encoded information and abstraction of the gist. In conclusion, our results indicate that sleep, even a nap, can potentiate the solution of problems that involve logical reasoning. Thus, sleeps function seems to go beyond memory consolidation to include managing of everyday-life events.

Sonolência diurna excessiva em adolescentes: prevalência e fatores associados

Objective: To assess studies on excessive daytime sleepiness in adolescents and to present a systematic review the prevalence and associated factors. Data sources: Papers found on PubMed and SciELO databases presenting original results without restriction of time and language were evaluated. Data synthesis: The prevalence of excessive daytime sleepiness ranged from 7.8 to 55.8%. The Epworth Sleepiness Scale and the School Sleep Habits Survey were the main tools used in the studies. Associations of excessive daytime sleepiness with sleeping-related problems, such as teeth gnashing, sleep apnea and insomnia, among others, were frequently described. The association of other biological, environmental and behavioral factors with excessive daytime sleepiness was not clearly assessed. Conclusions: Many factors, such as sedentary behavior and alimentary habits, were poorly investigated so far and presented controversial results when analyzed as variables related to excessive daytime sleepiness. A lack of epidemiological studies with Brazilian adolescents was identified.

DOES THE CHRONOTYPE CLASSIFICATION NEED TO BE UPDATED? PRELIMINARY FINDINGS

Traditionally, chronotype classification is based on the Morningness-Eveningness Questionnaire (MEQ). It is implicit in the classification that intermediate individuals get intermediate scores to most of the MEQ questions. However, a small group of individuals has a different pattern of answers. In some questions, they answer as “morning-types” and in some others they answer as “evening-types,” resulting in an intermediate total score. “Evening-type” and “Morning-type” answers were set as A1 and A4, respectively. Intermediate answers were set as A2 and A3. The following algorithm was applied: Bimodality Index = (∑A1 × ∑A4)2 − (∑A2 × ∑A3)2. Neither-types that had positive bimodality scores were classified as bimodal. If our hypothesis is validated by objective data, an update of chronotype classification will be required. (Author correspondence: brunojm@ymail.com)

Potential link between caffeine consumption and pediatric depression: a case-control study

BackgroundEarly-onset depressive disorders can have severe consequences both from developmental and functional aspects. The etiology of depressive disorders is complex and multi-factorial, with an intricate interaction among environmental factors and genetic predisposition. While data from studies on adults suggest that caffeine is fairly safe, effects of caffeine in children, who are in period of rapid brain development, are currently unknown. Furthermore, systematic research addressing the relationship between depressive symptoms in children and caffeine consumption is lacking.The present study examined the effects of caffeine consumption on depressed mood in children with depression and non-depressed participants.MethodsChildren and adolescents (n = 51) already enrolled in an ongoing longitudinal study, aged 9-12 years, were assessed for depressive symptoms with the Children Depressive Inventory (CDI). Psychopathological symptoms were assessed with the Child Behavioral Checklist (CBCL) and eating habits were assessed with the Nutrition-Behavior Inventory (NBI) [1]. The children were compared to control children without psychopathology attending public schools in a Southern Brazilian city.ResultsParticipants with CDI scores ≥ 15 (mean = 19; S.D. = 4) also had high NBI scores (mean = 52; S.D. = 19, p < 0.001) suggestive of a relationship between depressive symptoms and environmental factors, in this case nutrition/behavior. Additional linear regression adjusted statistical analysis, considering the factors of consumption of sweets and caffeine individually, showed that caffeine, but not sweets, was associated with depressive symptoms.ConclusionsThese findings indicate that depressed children consume more caffeinated drinks than non-depressed children. Nonetheless while a strong association between depressive symptoms and caffeine consumption among children was found, further research should investigate whether or not this association is due to a cause and effect relationship.

Effect of Morning School Schedule on Sleep and Anthropometric Variables in Adolescents: A Follow-Up Study

The aim of this study was to assess whether the shift from afternoon to morning classes reduces the duration of sleep and whether this reduction has any relation to body fat measurements. This is a follow-up study in which students (n = 379), 12.4 (SD ± 0.7) yrs old, were evaluated before and after the school schedule shift, with a 1-yr interval between the first and second data collections. Adolescents were divided into two groups: an afternoon-morning group (students who shifted from afternoon to morning classes) and an afternoon-afternoon group (students who remained in afternoon classes). The morning schedule of classes lasted from 07:30 and 12:00 h, and the afternoon schedule of classes lasted from 13:00 and 17:30 h. Self-reported bedtime, wake-up time, and time-in-bed were obtained. Body mass index, waist circumference, and body fat percentage were obtained by direct measures. The results showed a reduction of time-in-bed during weekdays for those students who changed to the morning session (p < .001). Analysis of covariance (ANCOVA) for repeated measures of anthropometric differences between afternoon-afternoon and afternoon-morning groups showed no effect of the school schedule change on weight gain. In conclusion, the time-in-bed reduction in the period analyzed cannot be considered to be a mediating factor to modifications in overweight anthropometric indicators. (Author correspondence: michelleb_fisio@yahoo.com.br)

Sono, trabalho e estudo: duração do sono em estudantes trabalhadores e não trabalhadores

The aim of this study was to investigate the duration of sleep and associated factors in working and non-working students. Data were analyzed on the sleep-wake cycle in 863 teenage students in Sao Paulo, Brazil. Adjusted analyses were performed to compare sleep duration in working and non-working students. 18.4% of the group worked, and 52% of the working students slept eight hours or less per night. Prevalence of short sleep duration was higher in working students of both sexes (males, p = 0.017; females, p < 0.001). Working students showed short sleep duration in the analysis adjusted for socioeconomic status, but short sleep was more frequent in older adolescents (p = 0.004) and in lower (p = 0.001) and middle (p = 0.011) socioeconomic classes. Although more working students were in night school, in the model adjusted for gender and socioeconomic status, working students in afternoon courses showed higher prevalence of short sleep duration (PR = 2.53; 95%CI: 1.68-4.12).