Available online at www.sciencedirect.com
ScienceDirect
Sleep and academic performance: measuring the
impact of sleep
Shelley Hershner
Sleep impacts academic performance. Past studies focused
on the negative influence of shorter sleep duration and poor
sleep quality on GPA. New novel sleep measures have
emerged. Sleep consistency measures how likely a student is
to be awake or asleep at the same time each day. Students with
greater sleep consistency have better academic performance.
A morning circadian preference and earlier classes are
associated with higher grades. Later high school start times
may increase sleep duration, but do not consistently increase
GPA, but improve mood and well-being. If a student is
struggling academically, screening for a sleep disorder is vital.
Devices are under development which may allow students to
better monitor their sleep habits, sleep consistency,
chronotype and sleep behaviors. For the proactive student,
these devices may enhance sleep behaviors and academic
performance. Schools need to develop sleep friendly policies
and interventions to promote healthy sleep for their students.
tasks allow a better understanding of the complex association of sleep, learning and memory.
Address
Sleep Disorders Center, Department of Neurology, University of
Michigan, Ann Arbor, MI, United States
This article will explore the implication of different sleep
measures and their impact on GPA and academic
performance.
Grade point average (GPA) is not a direct measurement of
learning or memory. A students’ GPA involves a complex
interaction between the student and their environment
[2]. Intelligence, motivation, work ethic, personality,
socioeconomic status, health problems, current and
past school systems, course load, academic program,
and test-taking abilities all influence GPA. Research on
sleep and GPA evaluate specific sleep aspects with the
understanding that these measures will not accommodate
the full physiologic facets of sleep. Associations with GPA
and sleep measures exist; however, the results are inconsistent [1]. Commonly researched sleep measures include
sleep duration, sleep quality, sleep regularity, sleep timing, and sleep disorders (Figure 1).
Corresponding author: Hershner, Shelley (shershnr@umich.edu)
Sleep duration
Current Opinion in Behavioral Sciences 2019, 33:51–56
This review comes from a themed issue on Cognition and perception
- *sleep and cognition*
Edited by Michael Chee and Philippe Peigneux
https://doi.org/10.1016/j.cobeha.2019.11.009
2352-1546/ã 2019 Elsevier Ltd. All rights reserved.
Introduction
Sleep is a biologic necessity. Why we sleep is not entirely
known but it is a phenomenon observed in some form in
all animals. Sleep is a vital component of learning and
memory consolidation. Conceptually it is important to
understand how research on memory and sleep is performed. Research protocols operate by teaching participants a simplified task, for example, visual processing,
and then testing the subject following a night of reduced
sleep duration [1]. The change in performance is attributed to the impact of sleep duration. These tasks are often
not real-world examples of the activities we perform in
our jobs or academically, but the narrowed focus of the
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Adequate sleep duration is individual and dependent on
age. The American Academy of Sleep Medicine [3]
recommends seven or more hours of nightly sleep for
adults, while the National Sleep Foundation [4] recommends adolescents obtain 8–10 hours of sleep and younger children significantly more. Ultimately everyone’s
sleep requirement is individual and the best gauge of
sufficient sleep is waking refreshed and feeling alert
during the day.
The majority of students obtain inadequate sleep [5,6].
Insufficient sleep is the limited opportunity for sleep
rather than the inability to sleep. Insomnia is the inability
to fall or stay asleep and should not be equated with
insufficient sleep [7]. Short sleep duration is associated
with cognitive effects [1,8], performance decrements,
cardiovascular disease [9], obesity [10], diabetes, all-cause
mortality, hypertension, decreased mood [11], increased
risk-taking behaviors and substance use [6].
Shorter sleep duration is associated with lower GPAs
[6,12,13]. Among university students those with a GPA
<3.0 had the shortest sleep duration [12]. This study also
demonstrated lower examination scores based on the
prior night’s sleep duration [12], although other studies
have not replicated this finding [13]. One of the first
studies on GPA showed adolescents aged 13–19 with
Current Opinion in Behavioral Sciences 2020, 33:51–56
52 Cognition and perception - *sleep and cognition*
Figure 1
Sleep
Disorders
Timing
Quality
Sleep
Regularity
sleep quality are problematic as poor sleep quality can be
manifestations of different aspects of sleep and daytime
dysfunction. Improvement in poor sleep quality requires
a more thorough evaluation from sleep latency, sleep
disturbance, sleep hygiene behavior, as well as daytime
dysfunction. This is difficult at an individual student level
and nearly unattainable at the school level. So although
sleep quality is an important measure, it is complicated to
design interventions which improve sleep quality.
Sleep regularity
Duration
Current Opinion in Behavioral Sciences
Sleep measures which impact academic performance and grade point
average.
average grades of a Cs went to bed later and obtained
3 hours less sleep per week than higher scoring students
(B’s and higher) [14]. Other cross-sectional and prospective studies have found variable results of the association
of shorter sleep duration and lower academic performance
[6,12]. Some of this variability linking GPA and sleep
duration may occur as some studies included other sleep
measure such as circadian preference and sleep quality.
Overall the data, much of it older, suggest that shorter
sleep duration is associated with lower grades, but other
sleep measures can have an impact.
Sleep regularity is a novel sleep measure with growing
evidence of importance. It measures how consistent a
person’s sleep and wake schedule is across the week. An
example of this measure is the Sleep Regularity Index
(SRI) [24] which calculates the percentage probability of
an individual being in the same state (asleep versus
awake) at any two time-points 24-hours apart. The index
is scaled such that an individual who sleeps and wakes at
the same times daily scores a 100, and an individual who
sleeps and wakes at random scores 0. The SRI does not
require a main daily sleep episode and therefore can be
used among populations with higher sleep variability such
as college students. Utilizing the SRI college students
were categorized into two groups: Regular and Irregular
sleepers (upper and bottom quartile of the SRI respectively). Total sleep duration was not different between
the groups. Sleep regularity was positively associated with
a higher GPA. An increase of 10 in SRI was associated
with an increase of 0.1 in the GPA. At the end of the 30day study there was a significant difference in GPA ( p <
0.02) between Irregular (3.42 0.34) and Regular (3.72
0.24) groups. Factors such as circadian misalignment
and light exposure contribute to the impact of sleep
irregularity on academic performance.
Sleep quality
Sleep quality is one of the most frequently utilized
measures in sleep research. There are multiple validated
sleep quality surveys with the Pittsburg Sleep Quality
Index [15] being one of the most common measures.
Sleep quality per Buysse et al. [15] is difficult to define as
it is a subjective report on sleep duration, sleep latency,
number of arousals and perceived depth of sleep. Poor
sleep quality is frequently reported by students [16,17].
Multiple studies have shown an association with poor
sleep quality and decreased academic performance
among almost all subsets of students [5,13,18,19,20].
In a study among adolescent males, internet use was a
mediator between sleep quality and GPA [21]. Overall it
appears that sleep quality [15,21,22] might have a stronger association with GPA than sleep duration [23,24].
The subjective experience of sleep, or sleep quality,
influences GPA. The challenging issue with sleep quality
is its subjective nature. Interventions to increase sleep
duration can be developed, but interventions to improve
Current Opinion in Behavioral Sciences 2020, 33:51–56
A study utilizing commercially wearable wrist devices
found that greater consistency of sleep, sleep quality, and
longer duration correlated with better grades [13]. Many
devices are available, but studies are challenging as
models, program algorithms, and even the commercial
availability of these wrist devices change frequently.
Wearable devices measureheart rate, steps, and movements. These devices uses movement and heart-rate
patterns to estimate sleep. In other words, less movement
and heart rate variability are deemed sleep periods and
specific sleep stages are based on proprietary algorithms.
A recent study found the accuracy of the automated
algorithm for sleep was 69%, with a Cohen’s kappa of
0.52 0.14 [25].
This particular study tested 100 students in an introductory college chemistry class and used measures of sleep
duration, quality, and sleep inconsistency before examinations and assignments. Sleep inconsistency was
defined as the standard deviation of the participant’s
daily sleep duration with a larger standard deviation
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Sleep and GPA Hershner 53
indicating greater sleep inconsistency. Sleep inconsistency correlated with lower academic performance [13].
These studies highlight that the consistency of sleep and
wake patterns have an impact on academic performance.
Consistency of sleep is particularly challenging for college
students who have variable sleep and wake patterns based
on having different daily schedules [12]. High school
students typically have a fixed wake up time, with ‘catch
up sleep’ on the weekends. Sleep educational programs
should highlight sleep consistency, while individual college-aged students may want to limit the variability in
their class start times.
Sleep timing
A person’s bed and rise time reflect two aspects: external
obligations and circadian preference. External obligations
which impact the timing of sleep are typically the first
obligation of the day, which for most students is the start
of school. When considering sleep specific measures,
school start time could be categorized under sleep duration or sleep timing. For this paper it will be considered
under sleep timing.
A recent study investigated timing of classes and GPA
[37]. Data from nearly two million students from Los
Angeles County showed a higher grade in the first two
classes of the day. The first class was 8 AM. The math
GPA increased by 0.072 (SD 0.006) and English GPA
by 0.032 (SD 0.006). This has an effect size equivalent
to increasing teacher quality by one-fourth standard deviation or half of the gender gap. Analysis was controlled for
gender, age, parental education, and low-performing and
high-performing students. At least three mechanisms
could contribute the difference between morning and
afternoon classes: changes in teachers’ teaching quality,
changes in students’ learning ability (stamina), or differences in morning and afternoon class attendance. Chronotype was not measured in this study. Similarly, college
students have lower grades in later classes despite a
longer sleep duration [27]. Each hour of every that classes
started later, GPA declined by 0.022 points. A later school
start time is beneficial from a mood, behavioral and
well-being perspective, but from an academic stand point,
the jury is still out.
Circadian preference
School start time
Student’s rise time is often dictated by school start time,
employment, or sports practice [12,26,27]. This review
will focus on school start time which is an area of robust
growth in the literature, legislature, and popular press.
Legislatively, in 2019 California passed Senate Bill 328 to
mandate a later school start time. Part of the momentum
for this law is that multiple studies have shown improvement in mood [28–30], substance use [29], tardiness and
disciplinary actions [31], and motor vehicle accidents [32]
when high school start times are delayed. Conflicting data
exist if a later school start time results in improved
academic performance (GPA and standardized tests)
and sleep duration.
A Cochrane review found no clear association with an
improvement in GPA as two studies reported significant
positive associations [33,34], one study reported a nonsignificant negative association [35], while another study
reported a significant negative association [36]. Other
reviews have also shown inconsistent results in regards
to academic performance [30].
The Cochrane review found 4 studies with an increase in
sleep duration with a later school start time; however,
these results should be interpreted cautiously due to
variability in research design and methodological limitations [34]. In a study on nine schools with variable
school start times, those schools with a later start time
students slept longer [29]. Another study demonstrated
that a 45-min delay in high school start time initially had
a longer sleep duration which did not persist later in the
semester [31].
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Circadian preference is a manifestation of a person’s
intrinsic internal clock and simplistically can be considered as a spectrum from ‘morning lark to night owl.’ This
means that at certain times of the day a student will be
more alert or less alert. A commonly used instrument to
measure circadian preference is the Morningness-Eveningness Questionnaire.
Circadian preference or chronotype can influence sleep
timing and GPA. Conceptually chronotype has an impact
on academic performance through several domains: sleep
duration, alertness, performance, as well on potentially
less measured aspects like conscientiousness and class
attendance [38]. The general the pattern has been that
evening chronotypes are associated with lower academic
performance [38–41] despite adequate performance on
measures of memory, processing speed, and cognitive
ability [42]. In a study of Iranian students, chronotype
(more morning-type) was positively associated with GPA
[43]. Chronotype correlated with school achievement
even after adjustment for the effects of intelligence
and gender. A morning chronotype was associated with
increased conscientiousness [38].
The timing of sleep and individual circadian preference
influence grade point average. Overall the data suggest
morning classes and students with a morning preference
have an academic advantage. For students who are significant night owls, interventions targeting students’ ability to fall asleep earlier is a crucial intervention. Further
research on school start time is needed with the realization that even if academic performance is not enhanced,
improvement in other measures such as mood, wellCurrent Opinion in Behavioral Sciences 2020, 33:51–56
54 Cognition and perception - *sleep and cognition*
Figure 2
100
90
80
70
60
% 50
GPA<2
GPA>2
40
30
20
10
0
OSA/Snoring RLS/PLMD
Insomnia
CRSD
Hypersomnia
Current Opinion in Behavioral Sciences
Risk of academic failure (GPA < 2.0) based on screening positive for a sleep disorder [39].
being, and motor vehicle accidents indicates successful
and essential metrics.
Sleep disorders
Sleep disorders are classified into multiple domains: sleep
related breathing disorders, central disorders of hypersomolence, circadian rhythm sleep wake disorders, sleep
related movement disorders, insomnia, and parasomnias
[7]. Students with sleep disorders are more likely to have a
lower GPA [23,44]. In a study among college students,
27% were at risk for at least one sleep disorder [39],
including obstructive sleep apnea, insomnia, hypersomolence, and restless legs syndrome, and circadian rhythm
sleep wake disorders. Student who did not screen positive
for a sleep disorder had a higher GPA (mean GPA = 2.82,
SD = 0.88) than those who reported at least one sleep
disorder (mean GPA = 2.65, SD = 0.99 p < 0.01). Students at risk of academic peril (GPA < 2.0) were more
likely to screen positive for a sleep disorder (Figure 2). In
a longitudinal study of entering college freshman, screening positive for a sleep disorder resulted in a lower GPA
and approached significance for a higher likelihood of
dropping out of school within three-years [41]. A study
evaluating sleep disturbances defined as insufficient or
non-restorative sleep, excessive daytime sleepiness, poor
sleep maintenance and sleep onset insomnia found lower
class retention and GPA [45]. Each additional day per
week with sleep disturbances increased the probability
that a first year student would drop a course by 14% and
lowered the GPA approximately 0.02.
Among students of different ages, the sensation of
‘restless/aching legs when falling asleep,’ a symptom
concerning for restless legs syndrome, occurred more
frequently among students categorized with a lower
Current Opinion in Behavioral Sciences 2020, 33:51–56
GPA [20]. In this study, snoring, a sign of obstructive
sleep apnea, was not significant for a lower academic
performance among 6th grade through college-aged students, although the sample size was small. Other studies
have found obstructive sleep apnea in school-age children
to be associated with poorer academic performance with
the best evidence of a negative impact on core domains of
math, language arts, and science [46].
Attention Deficient Hyperactivity Disorder (ADHD)
symptoms of inattention, hyperactivity, and impulsivity
can be the consequence of insufficient, poor-quality
sleep, or sleep disorders [47]. ADHD has been associated
with restless legs syndrome, periodic limb movements,
iron deficiency, snoring, and obstructive sleep apnea
[47,48].
A sleep disorder impacts academic success through several different means such as excessive daytime sleepiness, decreased mood, poorer general health, lower
motivation, decreased executive function or directly
through the sleep disorder itself [41]. These studies
highlight that when a student is struggling academically,
screening for a sleep disorder should be considered.
Among children presenting with an ADHD symptoms
or an ADHD diagnosis, screening for a co-morbid sleep
disorder should occur.
Future directions
Students have responsibility for their sleep patterns.
Devices are under development which help students be
more accountable for their sleep. A study using commercially available wearables developed specific algorithms to
investigate sleep regularity, sleep quality, sleepiness, and
chronotype [49]. The purpose of this study was for students
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Sleep and GPA Hershner 55
to better understand their own sleep measures to best
determine learning strategies, studying habits and behavior
decisions. This study did not investigate if sleep awareness
changed grade point average, but it is an intriguing concept
for students to self-align sleep measure with their own
academic goals.
Interventions are needed to improve sleep. For example,
a recent study with an 8-hour sleep challenge gave extra
credit for those students who slept more during the five
days of final examinations [50]. Study participants slept
98 min more each night than nonincentivized students
with equal academic performance despite a decrease on
average of 490 min of wakefulness as compared to the
nonincentivized students. Among the students who participated in the challenge, those students with a more
consistent sleep schedule performed better academically
on the final examination than students with a more erratic
sleep schedule. This study highlights that students can
embrace positive sleep-related behavioral changes even
at a disadvantaged time of the semester.
Conclusion
There are multiple ways to measure sleep and academic
performance. Much of the initial sleep and GPA literature
focused on sleep duration and sleep quality, with mixed
results. There are limitations to these sleep measuresspecifically sleep duration is typically by self-report and
sleep quality is subjective. Recently novel measures of
sleep have emerged. When we sleep and how consistently
we sleep may have the greatest impact on academic
performance. Knowledge of which sleep measures influence GPA is vital. Institutions have a responsibility to
develop interventions and policies to help students’ sleep
behaviors. Students are not immune to responsibility and
should improve their sleep behaviors to the best of their
ability. The sleep community, educators, and students
need to understand which sleep measures have greatest
impact and encourage their implementation among their
schools and students.
Conflict of interest statement
Nothing declared.
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