Sleep Characteristics and Interventions

MIND, BRAIN, AND EDUCATION
Internal and External Time
Conflicts in Adolescents:
Sleep Characteristics and
Interventions
F. M. Fischer1, B. Radosevic-Vidacek2, A. Koscec2, L. R. Teixeira1, C. R. C. Moreno1, and A. Lowden3
ABSTRACT—Daytime
fatigue and lack of sleep seem to increase throughout adolescent years. Several environmental,
psychological, and biological factors have been associated
with the development of sleep across adolescence. The aim of
the present article is to summarize these factors and to give
examples of various outcomes in sleep patterns among adolescents studied in different cultural settings. It is obvious
from earlier work that many adolescents have displaced circadian rhythms and lack of adaptation to school hours due to
an early school start or additional burdens for work. Several
interventions have aimed to help the adaptation process by
supporting sleep processes and changing scheduling, in this
way promoting classroom alertness. In summary, adolescents
worldwide shorten their sleep due to schoolwork hours and
additional work, especially by disturbing their sleep due to
circadian misalignment.
INTRODUCTION
Insufficient sleep and daytime sleepiness are commonly
increasing during the preadolescent and adolescent years
(Tynjälä, Kannas, & Valimaa, 1993). It has been suggested
that environmental, psychosocial, and biological factors
might underlie changes in sleep patterns across adolescence
1
Department of Environmental Health, School of Public Health, University of São Paulo
2
Zagreb Institute for Medical Research and Occupational Health
3
Stress Research Institute, Stockholm University
Address correspondence to F. M. Fischer, Department of Environmental
Health, School of Public Health, University of São Paulo, Avenida Dr.
Arnaldo, 715, 01246-904 São Paulo, Brazil; e-mail: fmfi[email protected]
Volume 2—Number 1
(Crowley, Acebo, & Carskadon, 2007). There are reasons to
believe that limitations in sleep recovery are widespread
among adolescents and affect negatively school and work
performance. It is therefore of great importance to highlight
possible solutions as to how to promote effective sleep behavior in relation to school- and work-related demands.
There are indications that at least some of the reduction
of sleep in adolescence can be attributed to school scheduling hours and the typical early start (approximately 08:00
hr) of school. Moreover, the differences in sleep onset
between weekdays and weekends among adolescents as a
result of school timing are well known (O’Brien & Mindell,
2005). An example of a biological factor is hormonal influence on sleep behavior at pubertal development. This phase
of life is recognized to be related to a phase delay of the circadian timing system (Andrade, Benedito-Silva, Domenice,
Arnhold, & Menna-Barreto, 1993; Carskadon, Vieira, &
Acebo, 1993).
Although individuals differ in sleep patterns, some general
sleep characteristics are age dependent. The drastic shortening of sleep needs from a daily average of 16 hr at birth to 10.5
hr at age 7 sums to around three fourth of an hour reduction
for each year of growth (Roffwarg, Muzio, & Dement, 1966).
After this, the reduction continues but at a slower pace. The
next 7-year period between ages 7 and 14 shows a reduction
from 10.5 to 8.5 hr (close to a reduction of 15 min for each
year). During the next 7-year period from adolescence through
adulthood (14–21 years), sleep need is further reduced down
to 7.75 hr (reduction of 10 min each year). Deviations from a
normal sleep length are typically initiated in adolescent years,
but other sleep-related phenomena are also occurring.
Longitudinal research designs have shown that subjective daytime sleepiness is more common in late puberty, suggesting that a greater sleep depth is found in this age group
© 2008 the Authors
Journal Compilation © 2008 International Mind, Brain, and Education Society and Blackwell Publishing, Inc.
17
Internal and External Time Conflicts in Adolescents
(Carskadon et al., 1980; Saarenpää-Heikkilä, Laippala, &
Koivikko, 2000; Strauch & Meier, 1988). Another possible
compensatory behavior of nocturnal lack of sleep is the fact
that incidence of napping seems to increase with age from
Grades 1 to 12 (Shinkoda, Matsumoto, Park, & Nagashima,
2000). Lack of sleep at young ages and daytime sleepiness can
also be part of an emerging symptom picture that indicates
the development of depression, sleep apnea, insomnia, or narcolepsy (Millman, 2005).
In general, adolescents show a delay in their sleep onset
(Thorpy, Korman, Spielman, & Glovinsky, 1988). Until the
1990s, the so-called delayed sleep phase syndrome was considered a consequence of behavioral changes. Whether the
reduction of sleep is a pure reflection of a biological maturation process is unclear because many cultural and psychosocial factors are also present in adolescent life, and the
occurrence of excessive sleepiness is widespread in adolescence (Millman, 2005).
Some studies have suggested the relevance of the social cultural context as an influence on sleep patterns among adolescents (Louzada & Menna-Barreto, 2003; Radosevic-Vidacek
& Koscec, 2004b). The common use of media devices has
been shown to contribute to increasing the sleep phase delay
(Van den Bulck, 2004). Natural and artificial light exposure
may also play a role in sleep behavior during adolescence. The
availability of electric lighting at home and consequent lifestyle changes can be factors related to sleep phase delay and
partial sleep deprivation (Louzada & Menna-Barreto, 2004).
The outcome of a poor circadian adaptation is mainly manifested in a shortening of sleep and daytime sleepiness. The
aim of the present article is to highlight such sleep patterns
in adolescents under different social cultural conditions. We
will discuss data that suggest that many adolescents show a
misalignment of circadian rhythms and are not fully adapted
to school time schedules. The effects for adolescents having
normal early school starts are reported. Effects of adolescents having extra work or alternative school schedules are
also evaluated. The interventions reported have aimed to ease
the circadian adaptation process to school scheduling by
promoting better sleep, changing scheduling, and reducing
sleepiness in school.
SLEEP IN ADOLESCENTS WITH NORMAL EARLY
SCHOOL STARTING TIMES
In a large international collaboration study including 11
European countries, each country studying a representative
group, 40,202 students between 11 and 16 years of age gave
questionnaire data on sleep habits (Tynjälä et al., 1993). The
results demonstrated a significant difference in sleep length
during a school week of about 1 hr within the European student population. The experience of morning tiredness was
18
very common (on at least four school mornings in a week) in
about 20%–37% of students in most countries. This study
showed that the inability to fall asleep was a common sleep
complaint among European adolescents. The 11- to 12-year-old
age group slept 9–10 hr, the 13- to 14 year-olds slept 8.6–9.6 hr,
and the 15- to 16 year-olds slept 8.3–9.2 hr. Occurrence of difficulty in falling asleep (26%–34%) has also been reported in
Canada (Laberge et al., 2001).
A Dutch study addressed 449 schoolchildren with fixed
morning start times while in seventh and eight grades in
elementary schools (mean age 11 years). It was demonstrated
that 43% of the responders had difficulty getting up in the
morning, 15% of them reported sleep problems, and 25%
did not feel rested at school (Meijer, Habekothe, & Van den
Wittenboer, 2000).
Another significant development of adolescent sleep—
apart from reductions of sleep length—is the increasing difference between sleep lengths taken during school days and
nonschool days (Carskadon & Dement, 1987). The difference
can be related to environmental factors such as the demands
of schoolwork (including early starts) and adolescents taking more power over their life and sleep scheduling. The outcome of such sleep scheduling is a significant shortening of
sleep during most part of the week and a possible recuperation at weekends. The discrepancy between weekend sleep
and weekday sleep has been shown in several studies to be
1–1.5 hr (Carskadon & Dement, 1987; Laberge et al., 2001).
Thus, there are strong indications that short sleep in connection to school scheduling elevates sleepiness at school and
likely also has a negative effect on learning (Fallone, Seifer,
Acebo, & Carskadon, 2002). From the outcome of adolescent
sleep studies, we can conclude that sleep duration is closely
associated with school scheduling hours. This was further
demonstrated in a study by Szymczak, Jasinska, Pawlak, and
Zwierzykowska (1993), where children were followed over
a year. They found that sleep in children increased during
vacations. If we consider mean sleep length during school
nights, the sleep outcome is much shorter than the sleep
need, and the reduction of sleep would resemble about 1 hr
in every 3 years during school years (Fallone et al, 2002).
Individual differences play an important role in shaping sleep habits. It is apparent that the effect of morningness–eveningness is significant in all age groups, also among
adolescents, and that particularly eveningness is associated
with less time in bed, more sleep debt, later bedtimes, more
irregular sleep habits, and higher consumption of alerting
stimulants such as coffee (Giannotti, Cortesi, Sebastiani, &
Ottaviano, 2002; Taillard, Philip, & Bioulac, 1999). Carskadon
et al. (1993) have shown that morningness–eveningness preferences are related to pubertal development and are geared
mainly by biological changes rather than mediated through
psychosocial factors.
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F. M. Fischer et al.
Gender difference studies are scarce in chronotype reports
(Giannotti et al., 2002) as well as in studies reporting sleep
habits among adolescents (Fallone et al., 2002; Tynjälä,
Kannas, & Levalahti, 1997). However, the weekend delay
of sleep is closely related to pubertal changes. Because girls
show a more rapid development, they also show later bedtime
habits than boys at least in early adolescence (10–13 years old;
Laberge et al., 2001).
In summary, we can conclude that adolescents around the
world shorten sleep according to age mainly by delaying timing of sleep due to biological and psychosocial reasons and
that they are subjected to premature forced awakenings in
connection to school days.
SLEEP AND DAYTIME FUNCTIONING OF
ADOLESCENTS ON A TWO-SHIFT SCHOOL
SCHEDULE
As we can see from the previous section, school schedule is
one of the external factors that has been named responsible
for some sleep characteristics of adolescents and their daytime functioning. Much attention has been paid to research of
sleep restriction imposed by early school start in single-shift
schools. In contrast, there are few studies reporting data on
sleep of adolescents who attend double-shift schools, even
though double-shift schools are common in many countries
(Bray, 1990). In a double-shift system, one group of students
usually attends school in the morning and the other in the
afternoon. Students can attend classes on a fixed shift schedule, that is, at the same time every school day, or can change
shifts, in some cases, on a weekly basis. A double-shift school
system quite differently impacts patterns of sleep and wakefulness as compared to a single-shift system, giving different
opportunities for sleep and putting different constraints on
the students.
The National Sleep Foundation (2000) recommendations
for healthy sleep state that optimal daytime functioning with
minimal sleepiness in adolescents requires from 8 hr 30 min
to 9 hr 25 min of sleep every night. Further, it is recommended
that adolescents should avoid large irregularities of sleep pattern and duration. Therefore, it was of interest to determine
what happens with sleep in adolescents on a two-shift school
schedule with respect to those recommendations for healthy
sleep.
A diary study of 17-year-old adolescents on fixed shifts
(Valdez, Ramirez, & Garcia, 1996) found that, on weekdays,
adolescents who attended school in the afternoon slept on
average longer (8 hr 35 min) than adolescents who attended
school in the morning (6 hr 40 min). However, in a study
which analyzed actigraphic sleep data of 13-year-old adolescents on fixed morning and afternoon shifts, a difference in
sleep duration between adolescents attending the morning
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shift and those attending the afternoon shift was not confirmed (Louzada & Menna-Barreto, 2004).
The studies of adolescents who attend school 1 week in
the morning and the other in the afternoon indicate that
adolescents prolong their sleep on school weeks with afternoon shifts. Namely, a large survey study found that 11- to 18year-old Croatian adolescents on average get a recommended
amount of sleep when on the afternoon shift (RadosevicVidacek & Koscec, 2003). This finding was further confirmed
in a diary study of sleep in 16-year-old Croatian adolescents
(Koscec, Radosevic-Vidacek, & Bakotic, 2006). Adolescents
reported on average 8 hr 35 min of sleep on an afternoon
schedule, in comparison to 6 hr 50 min of sleep throughout
the week of morning schedule. On the first weekend night
following the morning schedule, adolescents extended their
sleep, which was not the case on the weekend following the
afternoon schedule. This study also pointed to the advantage of an afternoon schedule regarding sleepiness upon
awaking. Beneficial effect of afternoon shifts for fulfilment
of adolescents’ sleep need was found also in a questionnaire
study of 15- to 18-year-old Greek adolescents who slept on
average 8 hr 49 min when on afternoon shifts, in comparison
to 7 hr 35 min when on morning shifts (Lazaratou, Dikeos,
Anagnostopoulos, Sbokou, & Soldatos, 2005).
Two-shift school systems, in which students change shifts,
facilitate irregularities of sleep pattern and sleep duration,
which is not consistent with recommendations stating that
adolescents should avoid large delay of bedtime and wake
time as well as large extension of sleep. However, with regard
to irregularity of sleep duration, the results indicate that
extension of main sleep when on afternoon shifts is used to
pay off insufficient sleep from morning shift days (RadosevicVidacek, Koscec, & Bakotic, 2006). On the other hand, there
is still a question of whether sleep irregularity has negative
impact on daytime functioning of adolescents. Pronounced
sleep delay and sleep extension observed between morning
and afternoon shifts were not found to be important predictors of daytime sleepiness, depressed mood, school grades,
or injuries of adolescents (Radosevic-Vidacek & Koscec,
2004a). Therefore, irregularity of sleep on afternoon shifts
with respect to morning shifts may not be viewed as a negative aspect of two-shift school schedules. Bedtime delay on
weekends with respect to morning shifts was the only measure of sleep irregularity that predicted sleepiness and injuries
of adolescents in a two-shift system. Sleep duration on morning shifts attained small predictive value for measures of daytime functioning. Morningness–eveningness preference was
a consistent predictor of self-reported measures of daytime
functioning in adolescents (Radosevic-Vidacek & Koscec,
2004a).
In families that were shifting their rhythms of sleep and
wakefulness due to engagement of parents in shift work and
engagement of adolescents in a two-shift school schedule,
19
Internal and External Time Conflicts in Adolescents
parental involvement in shift work somewhat increased
sleep loss and irregularity of sleep in adolescents (RadosevicVidacek & Koscec, 2004b). Further studies are needed to
examine whether living with shift-working parents exacerbates unhealthy sleep habits through reinforcement, modeling, or opportunities that make such sleep possible.
EFFECTS OF WORKING AND STUDYING ON SLEEP
AND SLEEPINESS AMONG STUDENTS
Young adults undergo intense physical, emotional, and cognitive development, aggravated by such factors as college
admission, establishment of important relationships, independence from their parents, and the beginning of a labor life.
During the past years, worries about the double journey of
studying and working have been discussed. The double journey (work and study) may result in or aggravate health problems, including sleep problems, as observed in previous
studies with high school students.
Machado, Varella, and Andrade (1998) compared female
evening college students who worked and did not work. It
was observed that female students who did not work went to
bed and woke up later than those who did work. The latter
had shorter sleep duration and more regular sleeping times
during weekdays than those who did not work.
Fischer, Oliveira, Teixeira, Teixeira, and Amaral (2003)
studied fundamental and high school students, attending
morning and evening classes, from 14 to 18 years old, living in
two small towns located in the countryside of the State of Sao
Paulo. The students were interviewed and answered a comprehensive questionnaire on sociodemographic items, working and living conditions, and health symptoms, including
sleep duration during working days and days off. This study
showed that working teens reported shorter sleep duration
during the week when compared to their colleagues who did
not work. During the weekend, those who worked reported
longer sleep times suggesting a building up of a sleep debt.
Teixeira, Fischer, Andrade, Louzada, and Nagai (2004a),
Teixeira, Fischer, Turte, and Nagai (2004b), and Vinha,
Cavalcante, and Andrade (2002) showed that working teens
have earlier awakenings, shorter sleep duration, more difficulties in waking up, and worse sleep quality than nonworking teens during working days. Conversely, during days off,
particularly on Sundays, working teens went to bed earlier
and had an easier awakening than nonworkers. Gender was
a significant factor associated with sleep duration, and males
showed shorter sleep than females. The female students
showed higher diurnal sleepiness and more sleep disturbances.
The weekly working time affected the sleep duration: those
working 40 hr and more had shorter sleep than nonworkers.
The data suggested that nonworker/unemployed female students had the largest consumption of alcoholic drinks.
20
Several other factors are associated with sleep duration
among working teens. A study carried out among high school
students in Sao Paulo, Brazil, using actigraphy showed that
some factors significantly associated with shorter sleep duration were as follows: age entering the labor force, workplace
and job title, wages, and quality of working conditions. Work
control is also included as an important variable affecting sleep
duration as well as high psychological demands, ability to perform tasks, and support from coworkers (Fischer et al., 2005).
Teixeira et al. (2007) showed that the sleepiness patterns
of working teens were significantly different from nonworkers, as they were sleepier on early mornings and late evenings.
Working teens face more difficulties in arriving at school on
time and in remaining in school during the school hours. A
U-shaped pattern of sleepiness was probably due to the circadian influence, and the rapid rise of sleepiness toward the
evenings reflected the sleep debt because students woke up
early in the morning (around 06:00 a.m.). Along the working week (Monday–Friday), sleepiness showed an additional
afternoon peak, a so-called “postlunch dip.” On Mondays,
sleepiness among teenage workers was likely to be associated
with changes in bed times and waking up times, as well as
extracurricular activities during the prior weekend.
In the same study, Teixeira et al. (2007) showed that students who did not work can follow the free expression of their
sleep–wake cycle, as they did not have to wake up early during
the weekdays for work. Thus, they express the phase delay of
sleep that is characteristic of puberty. As observed by the wrist
actigraphy assessments and diary data, the working students
went to bed almost immediately upon arriving home at night,
as they had to wake up early the next day to go to work.
The working students had shorter sleep periods during
all school days by about 2 hr/day compared to nonworking
students. The data support a cumulative loss of sleep across
weekdays in young workers. This seems to explain the differences in sleep patterns on weekends between the two groups:
workers went to sleep earlier than nonworkers, thus making
an advanced waking time possible.
Individuals submitted to more strict work hours and/or
school schedules tend to express more regular sleep–wake
cycles. In summary, school/work duties during workdays
seem to force working students to follow a stricter sleep–
wake routine than nonworkers.
INTERVENTIONS
Interventions on School Time Scheduling
To help adolescents to obtain enough sleep in connection
with school days with the standard early start, one solution
could be to impose sleep schedules that would optimize sleep.
One such attempt was made by Fallone et al. (2002) by asking children 6–12 years of age to either lengthen or reduce their
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F. M. Fischer et al.
sleep mainly by altering time for initiating sleep. Actigraphs
were used to evaluate sleep. The alterations of sleep averaged
3.5 hr and successfully demonstrated that children may be
able to change sleep by initiating bedtime earlier in the
evening. Unfortunately, this experiment lasted only for 1
week for each condition, and there was a lack of report on
sleep quality and how difficult the new sleep times were to
follow, and there were no reports on daytime sleepiness. But
it has been shown in similar sleep manipulations of children
9–12 years old that a lengthening of sleep of an hour also
shows positive effects on neurobehavioral functioning as
opposed to 1-hr reduction (Sadeh, Gruber, & Raviv, 2003). A
few studies have shown that a reduction of sleep in children
will increase daytime sleepiness. For example, in one study,
children’s sleep was restricted to 4 hr, and the results showed
that more sleepiness was detected (Fallone, Acebo, Arnedt,
Seifer, & Carskadon, 2001).
One other obvious way of treating sleep reductions in adolescence is to alter school start time. This type of intervention
has rarely been investigated although many schools, particularly in the United States, have decided to introduce a later
start (Fallone et al., 2002).
Carskadon, Wolfson, Acebo, Tzischinsky, and Seifer (1998)
followed a group of 25 students in the United States that during high school years were subjected to a 65-min earlier start
of their normal school day schedule (from 8.25 hr in Grade 9
to 7.20 hr in Grade 10). The results demonstrated that, despite
an earlier start, students did not go to bed earlier, and also the
dim light onset of melatonin phase in saliva was delayed. It
was concluded that adolescents show limits when trying to
make adjustments to an earlier scheduling of school days. A
number of cross-sectional studies have demonstrated that an
earlier start of the school day results in worse sleep and that
also there is a negative influence on daytime functioning as
well as grades (Epstein, Chillag, & Lavie, 1998; Wolfson &
Carskadon, 2003). But there still seems to be a lack of published studies evaluating a delay of school start times in a
robust interventional longitudinal design.
Interventions Using Bright Light
Some attempts to use light treatment during the morning
hours have been explored in order to advance the circadian
rhythm, promoting earlier bedtimes and sound sleep as well
as to elevate alertness in school and promote learning. One
such attempt was recently reported by Hansen, Janssen,
Schiff, Zee, and Dubocovich (2005) using bright light treatment (1,800 lux) during morning school hours in a high school
during November and February. A total of 60 students were
studied and they normally slept 7.0 hr in connection with
school days. The bright light treatment did not significantly
affect sleep length or timing according to sleep diary measures,
either on school days or at weekends. Also, performance and
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mood were very little affected. The lack of positive results can
possibly be associated with the strong delay of sleep rhythms
at weekends, academic pressure, or lack of control of individual overall daily exposures of light.
Interventions Dealing With Nutrition
Because a rhythmic misalignment with school scheduling does
not only affect sleep cycles, it is important to also consider
other circadian influences such as feeding behavior and metabolic consequences for school performance. For example, the
study by Saarenpää-Heikkilä et al. (2000) found a clear link
between late bedtimes, daytime sleepiness, and irregular
breakfast habits in adolescent years. Similar findings have been
reported in a sample of Japanese children between 12 and 14
years of age (Arakawa et al., 2001), where skipped breakfast/
later bedtimes also contributed to lowered mood and elevated
daytime sleepiness. Obesity has also been associated with
habitual short sleep episodes (Vioque, Torres, & Quiles, 2000),
and skipping breakfast and fast-food consumption are connected to weight gain in the transition period from adolescence
to adulthood (Niemeier, Raynor, Lloyd-Richardson, Rogers, &
Wing, 2006). To receive breakfast at school would delay the
timing of nutritional intake to a later circadian phase when
both appetite and the intestinal systems are activated, making
it possibly to ingest larger and possible more nutritional meals
(Lowden, Holmbäck, Åkerstedt, Forslund, & Lennernäs,
2001). It has also been demonstrated that students involved in
school breakfast programs show favorable and improved
school functioning on both psychosocial and academic
variables (Kleinman et al., 2002).
Intervention on Educational Programs
An educational program on sleep seems to give adolescents
with little knowledge about sleep some long-lasting effects
(Cortesi, Giannotti, Sebastiani, Bruni, & Ottaviano, 2004). A
sleep hygiene education program was presented to 58 adolescent students and the effects on self-reported sleep (diary),
sleepiness, and mental states were evaluated (de Sousa,
Araújo, & de Azevedo, 2007). The interventions were introduced during 1 week and contained several parts including
posters, interactive sleep education, lectures, a survey, and a
quiz. The program was evaluated before the intervention and
1 month after. Daytime napping was shown to be initiated
earlier with possible positive effects on sleep latency at night,
but no significant effects were obtained on sleep timing,
sleep quality, and alertness despite the very high occurrence
of sleep-related problems in the studied group. The authors
conclude that there is a need to further evaluate a more intensive and long-lasting interventional program with use of a
larger group of students and with the possibility of including
control groups.
21
Internal and External Time Conflicts in Adolescents
CONCLUSIONS
In summary, adolescents around the world shorten sleep
according to age mainly by delaying timing of sleep due to
biological and psychosocial reasons and that they are subjected to forced awakenings in connection with school days.
However, in some countries, double-shift school schedules
seem to have beneficial effects regarding the fulfilment of
sleep needs of adolescents.
More research is needed on adolescents to evaluate the
effects on promoting sufficient sleep on school days by various interventions, such as educational programs on sleep
hygiene, bright light treatment, breakfast programs, and
so forth, that can be of use in trying to alter sleep habits
by either self-selection or the influence of parental control.
The lack of positive results in intervention attempts may
be associated with several factors such as the strong delay
of sleep rhythms at weekends, academic pressure and extra
timework, and increased degrees of freedom in social life.
Governmental policies to prevent work injuries and implement health promotion programs among working teens
should take into account the negative factors associated with
the double journey of work and study.
Acknowledgments—The Croatian studies presented in this
article were supported in part by grants from the Ministry of
Science and Sports, Croatia (MZOS-0022007, MZOS-0220222411-2659) and by the European Sleep Research Society—
Sanofi-Aventis Grant 2004. The Brazilian studies of Fischer
et al. and Teixeira et al. were supported by the Federal
Research Agencies CNPq and CAPES, and the State of São
Paulo Research Agency FAPESP.
REFERENCES
Andrade, M. M., Benedito-Silva, A. A., Domenice, S., Arnhold, I. J.,
& Menna-Barreto, L. (1993). Sleep characteristics of adolescents: A longitudinal study. Journal of Adolescent Health, 14,
401–406.
Arakawa, M., Taira, K., Tanaka, H., Yamakawa, K., Toguchi, H.,
Kadekaru, H., et al. (2001). A survey of junior high school students’ sleep habit and lifestyle in Okinawa. Psychiatry and Clinical
Neurosciences, 55, 211–212.
Bray, M. (1990). The quality of education in multiple-shift schools:
How far does a financial saving imply an educational cost?
Comparative Education, 26, 73–81.
Carskadon, M. A., & Dement, W. C. (1987). Daytime sleepiness:
Quantification of a behavioral state. Neuroscience and Biobehavioral
Reviews, 11, 307–317.
Carskadon, M. A., Harvey, K., Duke, P., Anders, T. F., Litt, I. F., &
Dement, W. C. (1980). Pubertal changes in daytime sleepiness.
Sleep, 2, 453–460.
Carskadon, M. A., Vieira, C., & Acebo, C. (1993). Association between
puberty and delayed phase preference. Sleep, 16, 258–262.
22
Carskadon, M. A., Wolfson, A. R., Acebo, C., Tzischinsky, O., &
Seifer, R. (1998). Adolescent sleep patterns, circadian timing, and
sleepiness at a transition to early school days. Sleep, 21, 871–881.
Cortesi, F., Giannotti, F., Sebastiani, T., Bruni, O., & Ottaviano, S.
(2004). Knowledge of sleep in Italian high school students:
Pilot-test of a school-based sleep educational program. Journal
of Adolescent Health, 34, 344–351.
Crowley, S. J., Acebo, C., & Carskadon, M. A. (2007). Sleep, circadian rhythms, and delayed phase in adolescence. Sleep Medicine,
8, 602–612.
de Sousa, I., Araújo, J. F., & de Azevedo, C. V. M. (2007). The effect
of a sleep hygiene education program on the sleep–wake cycle
of Brazilian adolescent students. Sleep and Biological Rhythms, 5,
251–258.
Epstein, R., Chillag, N., & Lavie P. (1998). Starting times of school:
Effects on daytime functioning of fifth-grade children in Israel.
Sleep, 21, 250–256.
Fallone, G., Acebo, C., Arnedt, J. T., Seifer, R., & Carskadon, M. A.
(2001). Effects of acute sleep restriction on behavior, sustained
attention, and response inhibition in children. Perceptual and
Motor Skills, 93, 213–229.
Fallone, G., Seifer, R., Acebo, C., & Carskadon, M. A. (2002). How
well do school-aged children comply with imposed sleep schedules at home? Sleep, 25, 739–745.
Fischer, F. M., Oliveira, D. C., Nagai, R., Teixeira, L. R., LombardiJúnior, M., Latorre, M. R. D. O., et al. (2005). Job control, job
demands, social support at work and health among adolescent
workers. Revista de Saúde Pública, 39, 245–253.
Fischer, F. M., Oliveira, D. C., Teixeira, L. R., Teixeira, M. C. T. V.,
& Amaral, M. A. (2003). Efeitos do trabalho sobre a saúde de
adolescentes. Ciência & Saúde Coletiva, 8, 973–984.
Giannotti, F., Cortesi, F., Sebastiani, T., & Ottaviano, S. (2002).
Circadian preference, sleep and daytime behaviour in adolescence. Journal of Sleep Research, 11, 191–199.
Hansen, M., Janssen, I., Schiff, A., Zee, P. C., & Dubocovich, M. L.
(2005). The impact of school daily schedule on adolescent
sleep. Pediatrics, 115, 1555–1561.
Kleinman, R. E., Hall, S., Green, H., Korzec-Ramirez, D., Patton, K.,
Pagano, M. E., et al. (2002). Diet, breakfast, and academic performance in children. Annals of Nutrition & Metabolism, 46(Suppl.
1), 24–30.
Koscec, A., Radosevic-Vidacek, B., & Bakotic, M. (2006). Sleep patterns and sleepiness of adolescents attending school in shifts.
Journal of Sleep Research, 15(Suppl. 1), 123.
Laberge, L., Petit, D., Simard, C., Vitaro, F., Tremblay, R. E., &
Montplaisir, J. (2001). Development of sleep patterns in early
adolescence. Journal of Sleep Research, 10, 59–67.
Lazaratou, H., Dikeos, D. G., Anagnostopoulos, D. C., Sbokou, O.,
& Soldatos, C. R. (2005). Sleep problems in adolescence: A
study of senior high school students in Greece. European Child &
Adolescent Psychiatry, 14, 237–243.
Louzada, F. M., & Menna-Barreto, L. (2003). Sleep-wake cycle
expression in adolescence: Influences of social context. Biological
Rhythm Research, 34, 129–136.
Louzada, F. M., & Menna-Barreto, L. (2004). Sleep–wake cycle in
rural populations. Biological Rhythm Research, 35, 153–157.
Lowden, A., Holmbäck, U., Åkerstedt, T., Forslund, A., & Lennernäs, M.
(2001). Time of day and type of food—Relation to mood and
hunger during 24 hours of constant conditions. Journal of Human
Ergology, 30, 381–386.
Volume 2—Number 1
F. M. Fischer et al.
Machado, E. R. S., Varella, V. B. R., & Andrade, M. M. M. (1998).
The influence of study’s schedule and work on the sleepwake cycle of college students. Biological Rhythm Research, 29,
578–584.
Meijer, A. M., Habekothe, H. T., & Van Den Wittenboer, G. L.
(2000). Time in bed, quality of sleep and school functioning of
children. Journal of Sleep Research, 9, 145–153.
Millman, R. P. (2005). Working group on sleepiness in adolescents/
young adults; AAP Committee on Adolescence. Excessive sleepiness in adolescents and young adults: Causes, consequences,
and treatment strategies. Pediatrics, 115, 1774–1786.
National Sleep Foundation. (2000). Adolescent sleep needs and patterns.
Washington, DC: Author.
Niemeier, H. M., Raynor, H. A., Lloyd-Richardson, E. E., Rogers,
M. L., & Wing, R. R. (2006). Changes in dietary pattern in
15 year old adolescents following a 4 month dietary intervention with school breakfast—A pilot study. Nutrition Journal,
5, 33.
O’Brien, E. M., & Mindell, J. A. (2005). Sleep and risk-taking behavior in adolescents. Behavioral Sleep Medicine, 3, 113–133.
Radosevic-Vidacek, B., & Koscec, A. (2003). Sleep patterns of adolescents attending classes in two shifts. Shiftwork International
Newsletter, 20, 154.
Radosevic-Vidacek, B., & Koscec, A. (2004a). Effects of sleep preferences and sleep patterns on daytime functioning of adolescents
attending school in two shifts. Journal of Sleep Research, 13(Suppl.
1), 595.
Radosevic-Vidacek, B., & Koscec, A. (2004b). Shiftworking families:
Parents’ working schedule and sleep patterns of adolescents
attending school in two shifts. Revista de Saúde Pública, 38(Suppl.),
38–46.
Radosevic-Vidacek, B., Koscec, A., & Bakotic, M. (2006). Interindividual differences in napping and sleep extension in
Croatian adolescents attending school in two shifts. Journal of
Sleep Research, 15(Suppl. 1), 48.
Roffwarg, H. P., Muzio, J. N., & Dement, W. C. (1966). Ontogeny
development of the human sleep-dream cycle. Science, 152,
604–619.
Saarenpää-Heikkilä, O., Laippala, P., & Koivikko, M. (2000).
Subjective daytime sleepiness in schoolchildren. Family Practice,
17, 129–133.
Sadeh, A., Gruber, R., & Raviv, A. (2003). The effects of sleep restriction and extension on school-age children: What a difference
an hour makes. Child Development, 74, 444–455.
Volume 2—Number 1
Shinkoda, H., Matsumoto, K., Park, Y. M., & Nagashima, H. (2000).
Sleep-wake habits of schoolchildren according to grade.
Psychiatry and Clinical Neurosciences, 54, 287–289.
Strauch, I., & Meier, B. (1988). Sleep need in adolescents: A longitudinal approach. Sleep, 11, 378–386.
Szymczak, J. T., Jasinska, M., Pawlak, E., & Zwierzykowska, M.
(1993). Annual and weekly changes in the sleep-wake rhythm
of school children. Sleep, 16, 433–435.
Taillard, J., Philip, P., & Bioulac, B. (1999). Morningness/eveningness and the need for sleep. Journal of Sleep Research, 8, 291–295.
Teixeira, L. R., Fischer, F. M., Andrade, M. M. M., Louzada, F. M.,
& Nagai, R. (2004a). Sleep patterns of day-working, evening
high-schooled adolescents of São Paulo, Brazil. Chronobiology
International, 21, 239–252.
Teixeira, L. R., Fischer, F. M., Turte, S. L., & Nagai, R. (2004b).
Teen at work: The burden of a double shift on daily activities.
Chronobiology International, 21, 845–858.
Teixeira, L., Lowden, A., Turte, S., Nagai, R., Moreno, C. R. C., Latorre,
M. D. R. D. O., et al. (2007). Sleep and sleepiness among working
and non-working high school evening students. Chronobiology
International, 24, 99–113.
Thorpy, M. J., Korman, E., Spielman, A. J., & Glovinsky, P. B.
(1988). Delayed sleep phase syndrome in adolescents. Journal of
Adolescent Health Care, 9, 22–27.
Tynjälä, J., Kannas, L., & Levalahti, E. (1997). Perceived tiredness
among adolescents and its association with sleep habits and use
of psychoactive substances. Journal of Sleep Research, 6, 189–198.
Tynjälä, J., Kannas, L., & Valimaa, R. (1993). How young Europeans
sleep. Health Education Research, 8, 69–80.
Valdez, P., Ramirez, C., & Garcia, A. (1996). Delaying and extending sleep during weekends: Sleep recovery or circadian effect?
Chronobiology International, 13, 191–198.
Van den Bulck, J. (2004). Television viewing, computer game
playing, internet use, and self-reported time to bed and time
out of bed in secondary-school children. Sleep, 27, 101–104.
Vinha, D., Cavalcante, J. A., & Andrade, M. M. M. (2002). Sleep
wake patterns of student workers and non-workers. Biological
Rhythm Research, 33, 417–426.
Vioque, J., Torres, A., & Quiles, J. (2000). Time spent watching television, sleep duration and obesity in adults living in Valencia,
Spain. International Journal of Obesity, 24, 1683–1688.
Wolfson, A. R., & Carskadon, M. A. (2003). Understanding adolescents’ sleep patterns and school performance: A critical
appraisal. Sleep Medicine Reviews, 7, 491–506.
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