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The Relationships between Sleep-Wake Cycle and Academic Performance in Medical Students

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Survey and laboratory studies suggest that several factors, such as social and academic demands, part-time jobs and irregular school schedules, affect the sleep-wake cycle of college students. In this study, we examined the sleep-wake pattern and the role played by academic schedules and individual characteristics on the sleep-wake cycle and academic performance. The subjects were 36 medical students (male = 21 and female = 15), mean age = 20.7 years, SD = 2.2. All students attended the same school schedule, from Monday to Friday. The volunteers answered a morningness-eveningness questionnaire, the Pittsburgh Sleep Quality Index (PSQI) and kept a sleep-wake diary for two weeks. The relationships between sleep-wake cycle, PSQI, chronotypes and academic performance were analyzed by a multiple regression technique. The results showed that 38.9% of the students had a poor sleep quality according to the PSQI. When the medical students were evening type or moderate evening type the PSQI showed a tendency of poor sleep. The multiple regression analysis showed a correlation between sleep onset, sleep irregularity and sleep length with academic performance. These results suggest that chronotypes influence the quality of the sleep-wake cycle and that irregularity of the sleep-wake cycle, as well as sleep deprivation (average length was 6:52), influence the learning of college students.
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The Relationships between Sleep-Wake Cycle and
Academic Performance in Medical Students
Ana Ligia D. Medeiros, Denise B.F. Mendes, Patrícia F. Lima and John F. Araujo
Laboratório de Cronobiologia, Depto. Fisiologia, UFRN, Natal, Brazil
Abstract
Survey and laboratory studies suggest that several factors, such as social and academic
demands, part-time jobs and irregular school schedules, affect the sleep-wake cycle of
college students. In this study, we examined the sleep-wake pattern and the role played
by academic schedules and individual characteristics on the sleep-wake cycle and aca-
demic performance. The subjects were 36 medical students (male = 21 and female =
15), mean age = 20.7 years, SD = 2.2. All students attended the same school schedule,
from Monday to Friday. The volunteers answered a morningness-eveningness ques-
tionnaire, the Pittsburgh Sleep Quality Index (PSQI) and kept a sleep-wake diary for
two weeks. The relationships between sleep-wake cycle, PSQI, chronotypes and aca-
demic performance were analyzed by a multiple regression technique. The results
showed that 38.9% of the students had a poor sleep quality according to the PSQI. When
the medical students were evening type or moderate evening type the PSQI showed a
tendency of poor sleep. The multiple regression analysis showed a correlation between
sleep onset, sleep irregularity and sleep length with academic performance. These
results suggest that chronotypes influence the quality of the sleep-wake cycle and that
irregularity of the sleep-wake cycle, as well as sleep deprivation (average length was
6:52), influence the learning of college students.
Keywords: Medical student, academic performance, sleep-wake cycle, chronotype,
circadian rhythms.
Introduction
Survey and laboratory studies suggest that a number of factors, such as social and aca-
demic demands, affect the pattern of the sleep-wake cycle of healthy college students.
Other factors, including work and study schedules, influence sleep length and sleep-
wake cycle regularity. The circadian pacemaker controls the sleep-wake cycle and is
synchronized by light-dark cycle and by social contact. Results from Valdez et al.
Address correspondence to: Partrícia F. Lima, Laboratório de Cronobiologia, Depto. Fisiologia, UFRN,
Caixa Postal 1506, Natal, RN, Brazil. E-mail: patylima@mailbr.com.br
Biological Rhythm Research 0165-0424/01/3202-263$16.00
2001, Vol. 32, No. 2, pp. 263–270 © Swets & Zeitlinger
(1996) suggested that prolonged sleep during weekends are due to reduction of sleep
during workdays, whereas the delay of bedtime seems to be associated with a tendency
of the human circadian system to maintain a delayed phase. Machado et al. (1998)
showed that the tendency of phase delay on weekends was differently expressed accord-
ing to study’s schedules and work. They also suggested that the waking time on week-
days is set by study schedules, working schedules and other external factors.
Wever (1988) suggested that the desyncronization of circadian rhythms causes a
troublesome increase of stress and Jean-Louis et al. (1998) showed that students who
fell asleep in school experienced substantially greater negative mood states than those
who did not. The importance of the sleep-wake cycle for the physical, mental and
social health was shown by Pilcher and Ott (1998). The same study suggested that
the students submitted to stress, such as academic demands, had irregular sleep-wake
patterns and were presumably not as alert as they should be. In the present work, we
study the sleep-wake cycle patterns of a group of students, and the role played by the
irregularity of the sleep-wake patterns and individual characteristics on the quality of
sleep and academic performance.
Materials and Methods
The subjects were 35 medical students of the UFRN, with average age of 20.54 years
(SD = 2), 20 male and 15 female. They attended the same school schedules, with
classes beginning at 8:00 on Mondays, Wednesdays and Fridays and at 7:00 on Tues-
days and Thursdays. There were also classes from 14:00 to 17:00 on Mondays,
Wednesdays and Fridays. In the first day of the study, every student filled out an iden-
tification form with personal information, including their daily activities and health
problems, if they had any. All students were volunteers. They signed a term agreeing
to participate in the research and no monetary compensation was given. For two
weeks, the students recorded their sleeping and waking up schedules, as well as their
naps. The subjective sleep assessment, self-reported data on sleep diary and sleep
habits are frequently used in sleep-related research and have been highly correlated
with polygraphic measures of the sleep and wrist-worn activity monitor, the actigra-
phy (Lockley et al., 1999; Usui et al., 1999). It is important to know that all methods
that attempt to measure sleep, measure different things, i.e., subjetive recolletion of
sleep, electrical activity of the brain or motor activity.
A Portuguese version of the Horne & Östberg questionnaire (Horne & Östberg,
1976) was used to classify the participants of the research in morning type, evening
type or indifferent type, differentiating the moderate and extreme types, based on the
obtained value:
16–30: extreme evening type
31–41: moderate evening type
42–58: indifferent type
59–69: moderate morning type
70–86: extreme morning type
264 A.L.D. Medeiros et al.
The subjects completed the Pittsburgh Sleep Quality Index (PSQI) questionnaire,
which consists of 10 questions related with the normal sleep habits (Buysse et al.,
1989). It was applied during the second week of the data collection. Sleep quality
was considered bad for individuals who obtained a score higher than 5.
Sleep onset and sleep length were studied, as well as its deviation pattern. As quali-
tative variables, the chronotype and the quality of the sleep were analyzed. The results
of an exam taken during the collection of data were used to analyze the students’ aca-
demic performance. The standard deviation of sleep onset was used as an index of
irregularity of the sleep-wake cycle. For the statistical analysis of the data, a linear
regression test was applied with ANOVA to detect correlation among the several
studied variables.
Results
Our volunteers had a normal distribution of morningness-eveningness scoring
range (Fig. 1A), which was 25 indifferent types, 5 moderate morning types,
4 moderate evening types and 1 extreme evening type. The average of the sleep onset
was 0:03 ± 93min, and female students (23:44 ± 98min) went to sleep earlier than
male students (0:17 ± 90min). The average sleep length was 6:52 ± 93 min, which
is less than the general population, suggesting that our samples had partial sleep
deprivation.
The relationship between chronotype and sleep onset was statistically signifi-
cant (p < 0.04, Fig. 1B), which confirms that the data obtained in the Horne &
Östberg questionnaire are coherent. There was no statistically significant relationship
between chronotype and sleep length (p > 0.8), showing that, in spite of the differ-
ence in sleep schedules, sleep length was similar among morning and evening
types.
The standard deviation of the sleep onset of each student was used as an index of
irregularity of the sleep-wake cycle. The results showed a negative correlation
between irregularity of the sleep and score of the chronotype (p < 0.001), revealing
that the students who presented values tending to eveningness had a more irregular
sleep.
The analysis of the PSQI showed that 38.9% of the students had a poor sleep
quality during the study period. This high percentage is a result of the contribution
of the components 1 and 3 of the PSQI (subjective sleep quality and sleep length).
42.8% of the students had an irregular pattern of sleep-wake cycle (Fig. 2). A corre-
lation was also found between the irregularity of sleep and the PSQI (p < 0.05),
proving that irregularity of sleep implies bad quality of sleep.
The regression test also showed a correlation between sleep onset and academic
performance (p < 0.001) (Fig. 3A), between sleep length and academic perfor-
mance (p < 0.02, Fig. 3B) and between irregularity of sleep and academic per-
formance (p < 0.03, Fig. 3C), implying that the students with a more irregular
sleep-wake cycle and a shorter length of the sleep presented worse academic
performance.
Sleep-Wake Cycle and Academic Performance 265
Discussion
Other studies have shown that students without sleep deprivation (with sleep length
of 7:30h), but with an irregular pattern of the sleep-wake cycle presented sleepiness
during the day (Manber et al., 1996). Jean-Louis et al. (1998) showed a relationship
between day sleepiness and poor mood states in college students.
Billiard et al. (1987) showed that 13.6% of the students self-reported snoring.
Ficker et al. (1999) reported that 11.9% of the students snore frequently and are more
likely than non-snorers to have lower examination scores or even to fail their exams.
In our study, 13.8% of the students reported snoring but we did not find any
relationship between snoring and academic performance.
The decrement of academic performance on students who have an irregular sleep-
wake cycle could be explained by the internal desynchronization of the subjects’
rhythms. We are unable to demonstrate that these students are internally desynchro-
266 A.L.D. Medeiros et al.
Figure 1. Distribution of morningness-eveningness scoring range and the relationship
between the chronotype and the sleep onset of subjects.
Sleep-Wake Cycle and Academic Performance 267
Figure 2. Graphic of regular (a) and irregular (b) pattern sleep-wake cycle of subjects.
nized, but the irregularity of the sleep-wake cycle suggests this. Furthermore, these
students are under academic pressure. The irregularity of the sleep-wake cycle and,
perhaps, the internal desynchronization could be causing an increase of stress, and
the stress could be influencing their academic performance (Wever, 1988).
Several measures of human performance are controlled by circadian system and
recent research has proposed an endogenous two-oscillator model of the human cir-
cadian system, with one oscillator indicated by the core body temperature rhythm and
a second oscillator responsible for the daily sleep-wake cycle. When the subjects are
under altered sleep-wake pattern, the temperature rhythm and the sleep-wake cycle
may be separated from one another and run with different periods. This condition can
decrease performance efficiency, like in jet-lag and shift-work.
Students who showed a more regular sleep-wake cycle and longer sleep length
reported better academic performance. This is an evidence of the consequences of
insufficient sleep and irregular sleep-wake cycle. Although these consequences seem
obvious, unfortunately they are still often ignored. The results that showed worse aca-
demic performance in students who had irregular sleep-wake cycle and shorter sleep
length could reveal only one part of the consequences. Jean-Louis et al. (1998) pro-
posed a cascade into catastrophic events, such as decrement in academic performance,
disturbance of mood and behavior, and increased vulnerability to substance use.
Several published data appear to indicate that sleep deprivation or sleep fragmenta-
tion may impair the consolidation of newly learned information and the formation
268 A.L.D. Medeiros et al.
Figure 3. The linear regression shows a relationship between sleep onset (A), sleep length
(B), sleep irregularity (C) and academic performance.
of permanent memory trace during sleep (Giuditta et al., 1995). It is important to
emphasize that in our study and in others, we can only demonstrate statistical
relationships between chronotype and sleep irregularity and between sleep irregular-
ity and academic performance, without being able to prove a causal relationship. We
propose, however, that several exogenous factors, such as school schedules and
academic demands, and endogenous factors, such as chronotype and others, influence
the sleep-wake cycle and the quality of sleep, and that irregularity of the sleep-
wake cycle and poor sleep quality, as well as other factors, influence academic
performance.
Our results suggest that irregularity of the sleep-wake cycle as well as deprivation
of sleep (average length 6:52) influence the academic performance of college students.
We suggest that it is necessary to rethink the school schedules and to guide the students’
sleeping habits with the goal of reducing these negative effects on their learning.
Acknowledgements
We are grateful for the collaboration of the students. This work was supported by
CNPq and PPPg-UFRN.
References
Billiard M, Alperovitch A, Perot C, Jammes A (1987): Excessive daytime somnolence in
young men: prevalence and contributing factors. Sleep 10: 297–305.
Buysse DJ, Reynolds CF, Monk TH, Berman SR, Kupfer DJ (1989): The Pittsburg Sleep
Quality Index: a new instrument for psychiatric practice and research. Psychiatry Res
28: 193–213.
Ficker JH, Wiest GH, Lehnert G, Meyer M, Hahn EG (1999): Are snoring medical
students at risk of failing their exams? Sleep 22: 205–209.
Giuditta A, Ambrosini MV, Montagnese P, Mandile P (1995): The sequential hypothesis
of function of sleep. Special Issue: The function of sleep. Behav Brain Res 69:
157–166.
Horne JA, Östberg O (1976): A self-assesment questionnarie to determine morningness-
eveninhness in human circadian rhythms. Intern J Chronobiol 4: 97–110.
Jean-Louis G, von Gizycki H, Zizi F, Nunes J (1998): Mood states and sleepiness in
college students: influence of age, sex, habitual sleep, and substance use. Perceptual
and Motor Skills 87: 507–512.
Lockley SW, Skene DJ, Arendt J (1999): Comparison between subjetive and actigraphic
measurement of sleep and sleep rhythms. J Sleep Res 8: 175–183.
Machado ERS, Varella VBR, Andrade MMM (1998): The influence of study schedules
and work on the sleep-wake cycle of college students. Biol Rhythm Res 29: 578–584.
Manber R, Bootzin RR, Acebo C, Carskadon MA (1996): The effects of regularizing
sleep-wake schedules on daytime sleepiness. Sleep 19: 432441.
Pilcher JJ, Ott ES (1998): The relationships between sleep and measures of health and
well-being in college students: a repeated measures approach. Behav Med 23: 170–
178.
Sleep-Wake Cycle and Academic Performance 269
Usui A, Ishizuka Y, Obinata I, Okado T, Fukuzawa H, Kanba S (1999): Validaty of sleep
log compared with actigraphic sleep-wake state II. Psychiatry and Clin Neurosci 53:
183–184.
Valdez P, Ramirez C, Garcia A (1996): Delaying and extending sleep during weekends:
sleep recovery or circadian effect? Chronobiol Intern 13: 191–198.
Wever, RA (1988): Order and disorders in human circadian rhythmicity: possible relations
to mental disorders. In: Kupfer DJ, Monk TH, Barchas JD, eds., Biological rhythms
and mental disorders. Guiford Press, New York, pp. 253–346.
270 A.L.D. Medeiros et al.
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Sleep is often assessed in circadian rhythm studies and long-term monitoring is required to detect any changes in sleep over time. The present study aims to investigate the ability of the two most commonly employed methods, actigraphy and sleep logs, to identify circadian sleep/wake disorders and measure changes in sleep patterns over time. In addition, the study assesses whether sleep measured by both methods shows the same relationship with an established circadian phase marker, urinary 6-sulphatoxymelatonin. A total of 49 registered blind subjects with different types of circadian rhythms were studied daily for at least four weeks. Grouped analysis of all study days for all subjects was performed for all sleep parameters (1062–1150 days data per sleep parameter). Good correlations were observed when comparing the measurement of sleep timing and duration (sleep onset, sleep offset, night sleep duration, day-time nap duration). However, the methods were poorly correlated in their assessment of transitions between sleep and wake states (sleep latency, number and duration of night awakenings, number of day-time naps). There were also large and inconsistent differences in the measurement of the absolute sleep parameters. Overall, actigraphs recorded a shorter sleep latency, advanced onset time, increased number and duration of night awakenings, delayed offset, increased night sleep duration and increased number and duration of naps compared with the subjective sleep logs. Despite this, there was good agreement between the methods for measuring changes in sleep patterns over time. In particular, the methods agreed when assessing changes in sleep in relation to a circadian phase marker (the 6-sulphatoxymelatonin (aMT6s) rhythm) in both entrained (n= 30) and free-running (n= 4) subjects.
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Twenty-five young people (Y group), three elderly people and seven people with various sleep disorders (SD group) kept a sleep log for 2–7 days, and their wrist-activity was monitored simultaneously. The sensitivity and specificity of the sleep log, and the ratio of agreement between the sleep log and actigraphic sleep-wake state were calculated. The sensitivity and specificity in Y group were 87.93 ± 6.49% and 96.51 ± 2.37%, respectively. The sensitivity in SD group was significantly lower than in Y group. Even in Y group one-hour agreement ratios dropped during the sleep onset period.
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Despite the prevalence of sleep complaints among psychiatric patients, few questionnaires have been specifically designed to measure sleep quality in clinical populations. The Pittsburgh Sleep Quality Index (PSQI) is a self-rated questionnaire which assesses sleep quality and disturbances over a 1-month time interval. Nineteen individual items generate seven "component" scores: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication, and daytime dysfunction. The sum of scores for these seven components yields one global score. Clinical and clinimetric properties of the PSQI were assessed over an 18-month period with "good" sleepers (healthy subjects, n = 52) and "poor" sleepers (depressed patients, n = 54; sleep-disorder patients, n = 62). Acceptable measures of internal homogeneity, consistency (test-retest reliability), and validity were obtained. A global PSQI score greater than 5 yielded a diagnostic sensitivity of 89.6% and specificity of 86.5% (kappa = 0.75, p less than 0.001) in distinguishing good and poor sleepers. The clinimetric and clinical properties of the PSQI suggest its utility both in psychiatric clinical practice and research activities.
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To investigate the prevalence of excessive daytime somnolence and contributing factors, 58,162 draftees between 17 and 22 years of age, registered in two selection centers of the French army, were screened by means of a 17-item questionnaire. In response, 8,201 subjects (14.1%) reported occasional daytime sleep episodes, 2,210 (3.8%) one or two daily episodes, and 640 (1.1%) more than two daily episodes. Of the total sample, five percent or 2,933 considered these sleep episodes to affect their lives. Different possible factors of daytime sleep episodes were investigated, including hours of nocturnal sleep, sleep-wake schedule, sleep difficulties, use of hypnotics, snoring, and occurrence of cataplexy. A strong association was found between these factors and excessive daytime somnolence. A stepwise multivariate analysis was performed on five of these factors: hours of nocturnal sleep, sleep-wake schedule, sleep difficulties, use of hypnotics, and snoring. All five factors were shown to be independently related to excessive daytime somnolence and were ranked in the following descending order: use of hypnotics, sleep difficulties, irregular sleep-wake schedule, snoring, and hours of sleep.
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In addition to modulatory roles concerning bodily functions, sleep is assumed to play a main processing role with regard to newly acquired neural information. Elaboration of memory traces acquired during the waking period is assumed to require two sequential steps taking place during slow wave sleep (SWS) and eventually during paradoxical sleep (PS). This view is suggested by several considerations, not the least of which concerns the natural sequence of appearance of SWS and PS in the adult animal. While the involvement of PS in memory processing is well documented, the involvement of SWS is supported by the results of baseline and post-trial EEG analyses carried out in rats trained for a two-way active avoidance task or a spatial habituation task. Together with control analyses, these data indicate that the marked increase in the average duration of post-trial SWS episodes does not reflect the outcome of non-specific contingent factors, such as sleep loss or stress, but is related to memory processing events. Several considerations have furthermore led to the proposal that, during SWS, after a preliminary selection step, the first processing operation consists in the weakening of non-adaptative memory traces. The remaining memory traces would then be stored again under a better configuration during the ensuing PS episode. This view is in agreement with several relevant features of sleep, including the EEG waveforms prevailing during SWS and PS, as well as the ontogenetic sequence of appearance of SWS and PS. Some theoretical considerations on the role of sleep are also in agreement with the sequential hypothesis. More recent data indicate that the learning capacity of rats is correlated with several baseline EEG features of sleep and wakefulness. They include the average duration of PS episodes and of SWS episodes followed by wakefulness (longer in fast learning rats), and the waking EEG power spectrum of fast learning rats whose output is more balanced in the frequency range below 10 Hz than in slow learning and in non-learning rats. Additional EEG data suggest that fast learning rats may accomplish 'on line' processing of newly acquired information according to a sequence of events not dissimilar from the one proposed by the sequential hypothesis.