Journal of School Health School Start Times, Sleep, Behavioral, Health, and Academic …

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J Sch Health. Author manuscript; available in PMC 2017 May 1.
Published in final edited form as:
J Sch Health. 2016 May; 86(5): 363–381.

doi:  [ 10.1111/josh.12388 ]

PMCID: PMC4824552
NIHMSID: NIHMS746414
PMID: 27040474

School Start Times, Sleep, Behavioral, Health, and Academic Outcomes:
a Review of the Literature

Anne G. Wheaton , PhD,corresponding author Daniel P. Chapman , PhD, and Janet B. Croft , PhD

Anne G. Wheaton

Epidemiologist, Division of Population Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, 4770 Buford Hwy. NE, Mailstop F-78, Atlanta, GA 30341-3717, Phone: (770) 488-5362, Fax: (770) 488-5965, vog.cdc@9opi

Find articles by Anne G. Wheaton

Daniel P. Chapman

Epidemiologist, Division of Population Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, 4770 Buford Hwy. NE, Mailstop F-78, Atlanta, GA 30341-3717, Phone: (770) 488-5463, vog.cdc@2cpd

Find articles by Daniel P. Chapman

Janet B. Croft

Branch Chief, Epidemiology and Surveillance Branch, Division of Population Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, 4770 Buford Hwy. NE, Mailstop F-78, Atlanta, GA 30341-3717, Phone: (770) 488-2566, vog.cdc@0cbj

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Anne G. Wheaton, Epidemiologist, Division of Population Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, 4770 Buford Hwy. NE, Mailstop F-78, Atlanta, GA 30341-3717, Phone: (770) 488-5362, Fax: (770) 488-5965, vog.cdc@9opi ;
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corresponding authorCorresponding author.
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The publisher’s final edited version of this article is available at J Sch Health
See other articles in PMC that cite the published article.

Abstract

BACKGROUND

Insufficient sleep in adolescents has been shown to be associated
with a wide variety of adverse outcomes, from poor mental and physical
health to behavioral problems and lower academic grades. However, most high
school students do not get sufficient sleep. Delaying school start times for
adolescents has been proposed as a policy change to address insufficient
sleep in this population and potentially to improve students’
academic performance, reduce engagement in risk behaviors, and improve
health.

METHODS

This paper reviews 38 reports examining the association between
school start times, sleep, and other outcomes among adolescent students.

RESULTS

Most studies reviewed provide evidence that delaying school start
time increases weeknight sleep duration among adolescents, primarily by
delaying rise times. Most of the studies saw a significant increase in sleep
duration even with relatively small delays in start times of half an hour or
so. Later start times also generally correspond to improved attendance, less
tardiness, less falling asleep in class, better grades, and fewer motor
vehicle crashes.

CONCLUSIONS

Although additional research is necessary, research results that are
already available should be disseminated to stakeholders to enable the
development of evidence-based school policies.

Keywords: adolescents, school health, sleep, school start times, policy

BACKGROUND

Sleepy adolescents have doubtlessly been a problem for a long time. However,
it is only since the late 1980s that this issue has progressed from
teachers’ anecdotes of students falling asleep in class and parental
complaints of daily struggles to get their children out of bed to scientific
investigations into the causes and consequences of insufficient sleep.

Most adolescents may need at least 9 hours sleep per night 1 – 3 ; however, fewer than 8% of high school students
report getting this amount. 4 Less
than a third of students report 8 or more hours of sleep, and this proportion
decreases as school grade level increases so that fewer than a quarter of high
school seniors get this amount. 4
Healthy People 2020, a national initiative designed to guide disease prevention and
health promotion efforts to improve the health of all Americans ( http://www.healthypeople.gov/ ), contains 4 objectives related to
sleep, including one for adolescents. 5 This objective is to “increase the proportion of
students in grades 9 through 12 who get sufficient sleep (defined as 8 or more hours
of sleep on an average school night).”

Insufficient sleep in children and adolescents has been shown to be
associated with a wide variety of adverse outcomes in multiple aspects of their
lives from poor mental and physical health to behavioral problems and poor academic
grades. Insufficient sleep has been linked to excess weight, 6 – 13 decreased physical activity, 14 and increased food intake, possibly due to
alterations in appetite-regulating hormones. 12 Results of investigations into longitudinal changes in
weight attributable to sleep duration, however, have been mixed. 10 , 15

A solid body of literature has found that insufficient sleep in this young
population is tied to poor mental health, including depression, depressive
symptoms, 8 , 16 – 22
and suicidal ideation. 8 , 18 , 20 , 22 – 25 In addition, a few studies have
shown an association between insufficient sleep and unhealthy risk behaviors
including alcohol use, 17 , 19 , 20 , 22 tobacco
smoking, 20 , 22 marijuana use, 20 , 22 use of other
illicit/prescription drugs, 22
unhealthy weight control strategies, 26 and recent sexual activity. 20 Other factors that have been found to be associated with
insufficient sleep include risk-taking behaviors, 27 bullying, 28 school violence-related behaviors, 29 and physical fighting. 20 Short sleep duration has also been
found to be associated with a higher risk of unintentional injury. 30 Finally, students who do not get
enough sleep also may be more likely to have problems paying attention and poor
academic performance, 17 , 21 , 31 – 36 although
not all research agrees. 37 , 38 One of these negative studies
failed to find a correlation between school night sleep duration and grade point
average. 37 However, class
grading and subsequently grade point averages are not standardized and may vary by
subject, teacher, and school. That study also did not adjust by sex of student,
which was a strong predictor of grade point average. Ming et al. found that
“students with a sleep length of less than 7 hours on both weekdays and
weekends exhibited poorer performance, while those who made up this sleep loss on
weekends did not.” 38 That
study also relied on a non-standardized measure of academic performance and did not
adjust for variables such as grade in school, which is strongly related to
prevalence of insufficient sleep.

Adolescents tend to get insufficient sleep because of a combination of late
bedtimes and early rise times. External factors that contribute to later bedtimes
among adolescents include an increase in schoolwork; participation in afterschool
activities, including employment; fewer parent-set bedtimes; and late-night use of
technology in the bedroom. 39 – 43 Biology
also plays a part in later bedtimes among adolescents. One of the early changes
associated with puberty is alteration of a child’s circadian rhythms, such
that adolescents are more alert in the afternoons and evenings and require morning
sleep. 44 Their natural
body clocks can keep adolescents awake until 11 PM or later, in spite of going to
bed earlier and good sleep hygiene, such as avoiding stimulating activity at night
and minimizing caffeine intake in the afternoon or evening. 39 School-based sleep promotion
programs have been tried as a means of improving sleep hygiene among adolescents.
However, these programs may improve knowledge of sleep without having a significant
effect on behavior. 45 , 46

Rise times, on the other hand, are primarily determined by a single
factor—school start times. 43 Delaying school start times for adolescents has been proposed
as a policy change to address insufficient sleep in this population and potentially
to improve students’ academic performance, reduce engagement in risk
behaviors, and improve health. In 2014, the American Academy of Pediatrics published
a policy statement urging middle and high schools to adjust start times to permit
students to obtain adequate sleep and improve physical and mental health, safety,
academic performance, and quality of life. 3 This paper reviews studies examining the association between
school start times, sleep, and other outcomes including academic performance, mental
health, and motor vehicle collisions among adolescent students. This paper, and
especially the table provided, is intended to be a resource for educators, parents,
and other stakeholders who wish to learn more about the impact of changing school
start times for adolescents.

LITERATURE REVIEW

Methods

An outline of the steps in identification of articles and reports
included in the literature review is presented in the Figure . To be included in the review, analyses had to
include the variable of “school start time” either by comparing
different schools with different start times (cross-sectional) or the same
schools before and after changes in start times (longitudinal). Since the focus
of this review is on the effect of school start times on adolescent students,
studies that focused on elementary school (pre-middle school) students were
excluded. Additionally, reports had to be available in English, but could
include schools either in or outside the United States. Articles for the
literature review were initially identified through a PubMed search for
“school start time” OR “school start times”
(Step A). Some exclusions from this initial search included a study that
compared students in public or private schools to homeschooled
students, 47 a
comparison of adolescent sleep during summer and during the school
year, 48 and one that
modeled the effect of modifying school start times on the frequency of
encounters between child pedestrians and motor vehicles. 49 Another broader PubMed search
for “sleep” AND “adolescent” AND
“school” resulted in approximately 3200 articles (Step B).
Titles and abstracts were reviewed to identify studies that might meet primary
inclusion criteria. Full-text review of candidate articles confirmed inclusion
of articles for this review. Reference lists of articles identified in Steps A
and B and reviews of the topic of school start times were reviewed for
identification of additional reports (Step C). Several of the earliest studies
with results presented in abstract form only were identified in this
manner, 50 – 54 as were some studies from the
education or economics literature that were not indexed by PubMed. 55 – 59 A Scopus search for “school start
time” (all fields) found 320 documents (Step D), of which 3 satisfied
the inclusion criteria and had not been identified in previous steps. Finally
(Step E), one additional non-duplicative report was identified in the reference
list for articles in Step D. Final searches in Steps A, B, and D were conducted
July 1, 2015. For this review, 38 reports were reviewed for years of study,
study design, sample size, students’ ages, location, school start times,
outcomes, and key reported findings. Five of these reports are listed more than
once in the table. Three reports included multiple study populations whose data
are analyzed separately. 59 – 61 Three
reports included cross-sectional and longitudinal components, with data for each
component presented separately. 55 , 57 , 61

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Figure

Identification of Reports for Review

The primary limitation to this review is its reliance on indexing by
PubMed and Scopus, which could lead to omission of reports not indexed by these
databases. To address this limitation, we also examined the reference lists on
previous articles on the topic of school start times (Steps C and E). Five of
the 38 reports were identified in this manner. Publication bias and
over-representation of studies with significant results is also possible,
however, some studies included in this review had results that did not agree
with the majority.

Types of School Start Time Studies

We reviewed 38 reports on the impact of changes in school start time
(see Table ). Unfortunately, the earliest
reports, 50 – 54 which have been cited
frequently, were only published in abstract form. However, since they seem to
have provided the impetus for much of the subsequent research and are fairly
detailed, we have included them in this review. The studies presented in this
review can be categorized as either cross-sectional or longitudinal. The
cross-sectional studies simply compared characteristics for students at two or
more schools having different start times, such that School A had an earlier
start time than School B and compared how students at the two schools with
respect to such outcomes as sleep duration, school attendance, academic
performance, and morning traffic accidents among teens.

Table

Descriptions of School Start Time (SST) Studies in Preadolescents,
Adolescents, and College-Age Students

Study
Author(s)(Year)
Year(s) of Study
Study DesignSample SizeAgeLocationSchool Start TimesOutcomesKey Findings
Carskadon et al. (1998) 62
Not
specified
Longitudinal
(before vs after
SST
change)
26
(same students)
Grades 9–10Rhode IslandYear 1–9th grade: 8:25
Year
2–10th grade: 7:20
Sleep schedules (sleep diaries and
data
from electronic wrist monitors), multiple
sleep
latency tests, polysomnography.
Earlier SST associated with earlier rise time
(p <
.05), shorter sleep duration (p < .05),
shorter REM
latency (p < .05), shorter sleep latency on
multiple
sleep latency tests (p = .004), and more
students
with REM sleep during multiple sleep latency
tests
(p NR).
Epstein et al. (1998) 72
Not
specified
Cross-sectional
(students in
18
schools)
572Grade 518 schools
throughout Israel
Early risers: 7:10
(2+
times/week)
Regular risers: 8:00
Sleep duration, bedtime, rise
time
(weekdays and weekends), sleepiness,
daytime
functioning, sleep difficulties.
Early risers reported shorter weekday
sleep
duration (p = .0004), more complaints of
feeling
tired throughout the day (p = .045), more
daytime
sleepiness (p = .004), and more
difficulty
concentrating and paying attention (p = .0001).
Wahlstrom et al. (1998) 60
Not
specified
Cross-sectional
(3 districts)
NRGrades 10–12MinnesotaDistrict A
(Minneapolis):
8:30
District B: 7:25
District C:
7:15
School Sleep Habits Survey 35 (study,
work,
sleep, and school habits, and
preferences).
Later SST corresponded to later rise time (p
<
.0001), same bedtime, and longer weeknight
sleep
duration (p < .0001). Later SST also
associated
with less daytime sleepiness (p < .0001),
less
struggling to stay awake during academic tasks
(p
< .01 for A vs C), fewer tardies (p < .001),
less
falling asleep in morning classes (p <.005),
fewer
depressive symptoms (p < .001 for A vs C),
less
time spent at work during school week (p <
.05),
and higher self-reported grades (p < .05).
Wahlstrom et al. (1998) 60
Not
specified
Cross-sectional
(3 districts)
NRGrades 7–8MinnesotaDistrict A
(Minneapolis):
7:35
District B: 8:00
District C:
8:00
School Sleep Habits Survey 35 (study,
work,
sleep, and school habits, and
preferences).
Similar associations as in HS students. Later
SST
corresponded to longer sleep duration (p < .05
for
A vs C), same bedtime, and later rise time (p <
.05
for A vs C). Later SST also associated with
less
daytime sleepiness (p < .05 for A vs B),
less
struggling to stay awake during academic tasks
(p
< .05 for A vs B), lower depression scores (p
< .05
for A vs B), and less hours of homework (p
< .05
for A vs B and C).
Wolfson & Carskadon (1998) 35
1994
Cross-sectional
(students in 4
schools
in 3 public school
districts)
3120Grades 9–12Rhode Island7:10 – 7:30School Sleep Habits Survey
(study,
work, sleep, and school habits
and
preferences)
Students at school with earliest SST (7:10)
reported
earlier rise times than students at the other
schools
(p < 0.001). Other sleep related differences did
not
meet effect size criterion.
Baldus (2002) 63
Not specified
Longitudinal
(before vs after
SST
change)
31
(same recruits,
2 sleep
schedules)
US Navy
recruits
(mean
21.3
years)
Great Lakes,
Illinois
Early reveille: 9PM-5AM
sleep
time
Late reveille: 10PM-6AM
sleep time
Sleep duration.Later reveille associated with longer sleep
duration
(p = .01). The 10PM bedtime—6AM rise
time
resulted in 22 more minutes of sleep per night
per
recruit.
Wahlstrom (2002) 55
1994–2000
Longitudinal
(before vs after
SST
change)
>12 000 (7 HS)Grades 9–12Minneapolis,
Minnesota
Pre-change: 7:15
Post-change: 8:40
Class grades, attendance,
tardiness,
graduation rates, rates of
continuous
enrollment.
After SST change, % continuously
enrolled
increased (p < .05), attendance rates
increased
(among students not continuously enrolled) (p
<
.001), and letter grades increased slightly
(not
significant).
Wahlstrom (2002) 55
1997–2001
Cross-sectional
(Minneapolis HS
vs
District B)
467 (Minneapolis
HS)
169
(District B)
Grades 9–12Minneapolis,
Minnesota
Minneapolis HS: 8:40
District B:
7:30
School Sleep Habits Survey 35 (study,
work,
sleep, and school habits and
preferences).
Later SST corresponded to longer sleep
duration (p
< .001), same bedtime, and later rise time (p
<
.001). Later SST also associated with less
daytime
sleepiness (p < .01), less struggling to stay
awake
during academic tasks (p < .01), fewer tardies (p
<
.01)/absences (p < .05), less falling asleep
in
morning classes (p < .001), and fewer
depressive
symptoms (p < .05).
Dexter et al. (2003) 73
2002
Cross-sectional
(2 schools
with
different SSTs)
193 (School 1)
587 (School 2)
Grades 10–11Altoona (1) and
Chippewa
Falls
(2), Wisconsin
School 1: 7:50
School 2: 8:35
Weeknight sleep duration,
Epworth
Sleepiness Scale 91 .
Mean weeknight sleep duration was longer
in
School 2 compared to School 1 (p = .039).
Arlington Public Schools (2005) 81
2000–2002
Longitudinal (before
vs after SST
change)
3 HS, 5 MSGrades 7–11Arlington County,
Virginia
HS: 7:30 (2000–2001),
8:15
(2001–2002)
MS: 8:10 (2000–2001),
7:50
(2001–2002)
Academic grades (1st
period),
attendance, survey of
students’
perceptions of how alert and prepared
to
start school day, survey of
teachers’
perceptions of student behavior.
Surveys
were conducted in 2002 only.
Respondents were
asked to recall prior to
SST changes.
10th grade students’ 1st period grades
improved
after 45 minute SST delay (p < .001),
but
attendance appeared to decrease. No significant
change
in 7th grade students’ 1st period grades after
20 minute
SST advance.
Adam et al. (2007) 68
2002–2003
Cross-sectional24545–z19 yearsNationally (USA)
representative
NRSleep duration, bedtime, rise
time
(weekdays and weekends).
For older children (12–19 years), an
hour later SST
was associated with 0.57 hour more weekday
sleep
(p < .01), a 0.62 hour later rise time (p <
.01), and
no difference in bedtime.
Wolfson et al. (2007) 64
2003–2004
Cross-sectional
(2 schools
with
different SSTs)
205Grades 7–8Urban New
England
school
district
Early school: 7:15
Late school:
8:37
School Sleep Habits Survey 35
(sleep
duration, bedtime, rise time—weekdays
and
weekends, sleepiness, sleep-wake
behavior problems, sleep hygiene
scale),
official academic performance,
attendance,
tardiness.
Late SST associated with later bedtimes (in
autumn
only) (p < .05), later rise times (p <
.001), longer
sleep duration (65 minutes) (p < .001),
less
weekend oversleep (in autumn only)(p < .001),
less
daytime sleepiness in the autumn (p < .05),
fewer
sleep-wake behavior problems in the spring (p
<
.05), higher grades (8th grade only) (p < .01),
and
fewer tardies (p < .001). Weekend sleep
patterns
were similar.
Danner and Phillips (2008) 74
1998–1999
Longitudinal
(before vs after
SST
change)
9966 (Year 1)
10 656 (Year
2).
Sample size
included HS and
MS students,
but
results only
presented for HS
students.
Grades 6–12KentuckyYear 1 (Y1): 7:30 (HS)
Year 2 (Y2):
8:30 (HS)
Bedtime and rise time (weekdays
and
weekends), number of naps, Epworth
Sleepiness
Scale 91 , how
time spent
before and after school, motor vehicle
crash
rates among 17- and 18-year-old
students.
Compared to Year 1, in Year 2 students
reported
longer average sleep duration (p < .001), less
catch-
up sleep on weekend nights (p < .001), and
lower
scores on the Epworth Sleepiness Scale (p <
.001).
Crash rates in the study county decreased after
the
SST delay (p < .01).
O’Malley and O’Malley
(2008) 56
2001–2004
Longitudinal
(before vs after
SST
change)
297 (pre-delay)
977 (post-delay)
Grades 9–12Wilton,
Connecticut
Pre-delay: 7:35
Post-delay: 8:15
Condensed School Sleep
Habits
Questionnaire 35 .
Later SST corresponded to longer weeknight
sleep
duration (p < .001), later rise time (p <
.001), later
bedtime (p = .03), and fewer problems
with
sleepiness (p < .001).
Owens, Belon, Moss (2010) 65
2008–2009
Longitudinal
(before vs after
SST
change)
201 (mostly
boarders)
Grades 9–12Rhode IslandPre-change: 8:00
Post-change: 8:30
Bedtime and rise time (weekdays
and
weekends), sleepiness-related behaviors,
health center
visits, absences/tardies.
Delayed SST associated with longer school
night
sleep durations (p < .001), earlier bedtimes (p
<
.001), later rise times (p < .001), greater
sleep
satisfaction (p < .001), less sleepiness (p
< .001),
less sleepiness-related behaviors (p <
.001), less
depressed mood (p < .001), fewer visits to
health
center for fatigue-related symptoms (p = 0.03),
and
fewer absences/tardies (p < .05).
Zhang et al. (2010) 66
Not specified
Cross-sectional4470
(mother-
father-child
community based
trios)
Mean age 9.2
± 1.8y
Hong KongMorning school: ~7:35
Whole-day
school: ~8:08
Afternoon
school:
~12:54pm
Bedtime, rise time,
time-in-bed
(weekday, weekend, & long
holidays),
napping
Students in morning schools (earliest SST)
had
earliest bedtimes & rise times, shortest
time-in-bed,
most weekend sleep compensation, and
largest
proportion of daytime napping.
Carrell et al. (2011) 58
2004–2009
Cross-sectional6165U.S. Air
Force
Academy
freshmen
Colorado Springs, ColoradoEarly (2004–2005,
2005–
2006): 7:00. Middle (2006–
2007):
7:30. Late (2007–
2008, 2008–2009):
7:50.
For each schedule, some
students had a first
period
class while others did not.
Academic grades by
scheduling
characteristics.
Students assigned to a first period course
had
poorer grades; however, this association became
weaker
and became statistically insignificant as the
start time moved
from 7:00 AM to 7:50 AM.
Students performed worse in first period
classes
compared to other periods, but those with
first
period classes also performed worse in
their
subsequent classes on that schedule day.
Hinrichs (2011) 59
1993–2002
Cross-sectional
(primarily, but with
a
longitudinal
component)
196,617
observations
(may
include repeat test
takers) (students
from 73
schools)
Grades 10–12Twin Cities
metropolitan
area
(Minneapolis-St.
Paul, Minnesota)
7:15–8:40ACT scores, attendance ratesNo association between SST and ACT scores
or
attendance rates.
Hinrichs (2011) 59
2000–2006
Cross-sectionalApproximately 400
public high
schools
Grades 10–12Kansas (public
high schools in
the
state)
Mean (SD): 7:59 (0:15)School-level test score data on
Kansas
Mathematics Assessment, Reading
Assessment, Science
Assessment, and
Social Studies Assessment.
No association between SST and scores on
reading,
mathematics, science, and social
studies
assessments.
Hinrichs (2011) 59
2000–2007
Cross-sectional75 schoolsGrades 9–12?
(not
specified
in report, but
described as
high
schools)
Virginia suburbs of
Washington
D.C.
Scores on standardized
end-of-course
exams.
No association between SST and test
scores.
Lufi et al. (2011) 70
Not specified
Longitudinal
(before vs after
SST
change—short term
change only)
47Grade 8IsraelEarly class: 7:30
Late class: 8:30
Sleep duration, bedtime, rise time,
sleep
efficiency (data from electronic wrist
monitors),
attention tests.
Later SST associated with longer sleep
duration (p
< .01) and improved attention (p <
.01).
Ming et al. (2011) 38
Not specified
Cross-sectional1941 (students
from 2 public
high
schools, 1
vocational high
school, and
two
extracurricular
high school
programs
whose
students came from
various high
schools
throughout
the state)
Grades 9–12New JerseyVaried from 7:00 to 8:45
For analyses,
early SST
(before or at 7:30) vs late
SST (after
7:30)
Sleep duration, bedtime, rise
time,
napping, perceived sleep adequacy, night
awakenings,
prolonged sleep onset
Early SST associated with short weekday
sleep
duration (<7 hours, p < .0001), lower
likelihood of
receiving adequate night sleep (p < .0001),
and
higher likelihood of afterschool naps (p <
.0001)
and night awakenings (p =NR).
Vorona et al. (2011) 87
2007–2008
Cross-sectional
(2 cities
with
different SSTs in
public schools)
NR16–18 yearsVirginia Beach
and
Chesapeake,
Virginia
Early schools (Virginia
Beach):
7:20–7:25
Late schools
(Chesapeake):
8:40–8:45
Motor vehicle crash rates in each city.Crash rates among 16-to 18-year-olds were
higher
(p < .01) in Virginia Beach (which has
earlier
SSTs).
Yilmaz et al. (2011) 75
2008
Cross-sectional344115–18 yearsGaziantep, TurkeyEarly: 7:00–8:00
(morning)
Late: 12:00–12:40 pm
(afternoon)
Bedtime, rise time, sleep
latency
(weekdays & weekends), ideal night
sleep
time, napping, sleep hygiene
Compared to those with afternoon SSTs,
students
with morning SSTs reported shorter night
time
sleep on weekdays and weekends (p < .001)
and
shorter ideal night time sleep (p < .001). Early
SST
students were more likely to report daytime
napping
and needing help to awaken in the morning
(p < .001) and
less likely to report a long sleep
latency (>30 minutes)
on weekdays and weekends
(p < .001).
Vedaa et al (2012) 78
Not specified
Cross-sectional55
students
(intervention
school)
51
students
(control school)
Grade 10NorwayIntervention school: 9:30
(Mondays),
8:30 (rest of
week)
Control school: 8:30
(all
days)
Karolinska Sleepiness Scale 92 , reaction
time
tests, Positive and Negative Affect
Schedule, sleep diary
Compared to control school students, students
at
intervention school slept >1 hour longer on
Sunday
night (p < .05), had a smaller difference
between
Saturday and Sunday night sleep duration (p =
.04),
and shorter sleep latency on Sunday night.
Students
at the intervention school had fewer lapses
on
reaction time tests (p = .02) and faster reaction
times
(p = .02) on Monday than Friday compared
to the control students.
No differences in sleepiness
or positive or negative affect.
Edwards (2012) 57
1999–2006
Cross-sectional
component
20,530
students
(1999–2000)
27,686
students
(2005–2006)
Grades 6–8Wake County,
North Carolina
7:30–8:45 (53% of
students
start at 7:30, 22% start at
8:15)
End of year standardized test scores
in
reading and math; time spent watching
television and
doing homework;
absences
Later SST corresponded to higher standardized
test
scores on both math and reading tests (1 hour
later
corresponded to 3 percentile increase), less
time
watching television, more time doing homework,
and
fewer absences.
Edwards (2012) 57
1999–2006
Longitudinal
component (before
vs
after SST change for
schools that changed
SST
between 1999-
2006)
20,530
students
(1999–2000)
27,686
students
(2005–2006)
Grades 6–8Wake County,
North Carolina
7:30–8:45 (Some schools
started
earlier and some
started later after SST
change)
End of year standardized test scores
in
reading and math; time spent watching
television and
doing homework
Later SST corresponded to higher standardized
test
scores on both math and reading tests (1 hour
later
corresponded to 2 percentile increase in math
and
1.5 percentile increase in reading), less
time
watching television, and more time
doing
homework.
Borlase et al (2013) 69
1999–2008
Longitudinal (before
vs after SST
change
in 2006)
212 students in
Grades 9 and
12
(1999)
455 students in
Grades 9, 11,
and
12 (2008)
13–17 yearsWellington, New
Zealand
Senior students (Grade
12): 9:00 (pre),
10:30
(post)
Junior students (Grades 9,
11): 9:00
(no change)
School Sleep Habits Survey 35 (study,
work,
sleep, and school habits, and
preferences), technology use,
Epworth
Sleepiness Scale 91 , morningness-
eveningness preference,
sleep/fatigue
problems
Grade 12 students after the SST delay (2008)
had
longer sleep duration (p < .01), earlier bedtime (p
<
.01), later rise time (p < .001), less
sleep
discrepancy (sleep duration on school nights
vs.
non-school nights)(p < .01), and less sleepiness
(p
< .01) compared to Grade 12 students before
the
delay or Grade 11 students (2008).
Li et al. (2013) 36
2007–2009
Cross-sectional/
Longitudinal
(6
schools before vs
after SST change)
525 (baseline)
553 (2-year
follow-
up)
Grades 4–5
(mean
age
10.8y)
Shanghai, China2 control schools, no
change in SST:
7:30
2 schools, intervention 1:
7:30 (pre), 8:00
(post)
2 schools, intervention 2:
7:30 (pre), 8:30
(post)
Sleep duration, bedtime, rise
time,
daytime sleepiness (Chinese version
of
Children’s Sleep Habits Questionnaire)
At baseline, students at the 6 schools had
similar
sleep characteristics. At follow-up, later
SST
associated with later bedtime (p < .05), rise time
(p
< .001), longer sleep duration (p < .001), and
less
daytime sleepiness. Comparing baseline to follow-
up,
mean sleep duration decreased for students at
control schools (no
change in SST) but increased
for students at intervention
schools.
Perkinson-Gloor et al. (2013) 34
2010–2011
Cross-sectional2373 (early)
343 (delayed start)
Grades 8–9Mid-size city
in
northwestern
Switzerland
Early: not specified
Delayed: 20
minutes later
Sleep duration, bedtimes, rise
times
(weekdays and weekends), daytime
sleepiness,
behavioral persistence,
attitude towards life, school
grades
(mathematics and German language).
Later SST associated with longer weeknight
sleep
duration (p < .001), later weeknight bedtimes (p
=
.04 boys, p < .001 girls), later weekday rise
times
(p < .001), and less daytime sleepiness (p
< .001
boys, p = .03 girls).
Short et al. (2013) 76
1997–2000
(U.S.)
2008–2010 (Australia)
Cross-sectional302 (U.S.)
385 (Australia)
Grades 9–12
(mean
age
16.0y) (U.S.)
Years 9–11
(mean
age
15.6y)
(Australia)
Rhode Island
(U.S.)
South
Australia
(Australia)
U.S.: ~7:45
Australia:
8:20–9:00
School Sleep Habits Survey 35 (study,
work,
sleep, and school habits and
preferences), 8-day sleep diary
School night sleep duration correlated with
SST (r
= .29, p < .001). SST had largest effect on
sleep
duration (compared with parent-set bedtimes
and
extra-curricular load).
Boergers, Gable, and
Owens
(2014) 67
2010–2011
Longitudinal (before
vs after SST
change)
197 (boarding
students)
Grades 9–12Rhode IslandPre-delay: 8:00
Post-delay: 8:25
School Sleep Habits Survey 35 (study,
work,
sleep, and school habits and
preferences), caffeine
intake
questionnaire
After SST delay, mean wake times (school
days)
were later (p < .001), mean school night
sleep
duration was longer (p < .001), school
night
bedtimes did not change. The percentage who
slept
≥8 hour on school nights increased from 18%
to
44% (p < .001). There were no changes
in
nonschool night sleep patterns. After delay,
sleepiness
scores (p < .001), depression scores (p <
.001),
and caffeine use decreased (p < .05). No
changes in
number of hours engaged in athletics,
extracurricular activities,
and homework were
reported. No changes in self-reported grades
were
reported. Weekday sleep duration decreased
to
baseline after reverting to pre-delay SST.
Escribano & Diaz-Morales
(2014) 77
Not specified
Cross-sectional
(students in
3
schools)
66912–16 yearsMadrid, Spain8:00, 8:15, 8:30Bedtimes, rise times, sleep
duration,
attention task (at 3 times during school
day on
2 consecutive Wednesdays),
morningness/eveningness,
inductive
reasoning
Average school night sleep was more than
30
minutes longer for 8:30 SST than 8:00 SST (p
<
.001). Attention level highest for 8:15 SST on
first
Wednesday (p < .001), but no difference by SST
on
second Wednesday. Inductive reasoning score was
lowest
for 8:30 SST (p < .01).
Chen et al. (2014) 79
2009
Cross-sectional4801 (students
from 12 senior
HS
and 12 junior HS)
11–20 yearsShanghai, ChinaDichotimized: Before 7:00
vs. 7:00 or
later
Adolescent Sleep Wake Scale 93 ,
bedtimes,
wake-up times, sleep duration
(weekdays & weekends),
parents’ sleep
habits
SST before 7:00 associated with sleeping
<8 hours
(p = .015).
Vorona et al. (2014) 88
2009–2011
Cross-sectional
(2 counties
with
different SST in
public schools)
16–18 yearsChesterfield
County,
Virginia
and Henrico
County, Virginia
Early (Chesterfield): 7:20
Late
(Henrico): 8:45
Weekday motor vehicle crash
rates
during the school years (September-
May)
2009–2010 and 2010–2011.
In 2009–2010, crash rates among
16–18 year olds
were higher (p < .05) in
Chesterfield County
(which has earlier SST). In
2010–2011, crash rates
among 16–17 year olds were
higher (p < .05) in
Chesterfield County, but difference
was not
statistically significant when 18 year olds
were
included in comparison (p = .09). Adult crash
rates
for the same time periods did not differ between
the
two counties.
Milic et al. (2014) 80
2011
Cross-sectional821
(students from 4
HS)
15–19 yearsOsijek, CroatiaEarly: 7:00 AM or 1:00 PM
(alternating
weeks)
Late: 8:00 AM or 2:00 PM
(alternating weeks)
Epworth Sleepiness Scale 91 ,
morningness/eveningness,
napping,
academics (final semester grade)
Students with earlier SST performed
better
academically and had earlier chronotypes
(morning
preference) (p < .001). No difference in
sleepiness.
Wahlstrom et al. (2014) 61
2011–2013
Cross-sectional9089Grades 9–125 HS in Minnesota,
2 HS in
Colorado,
1 HS in Wyoming
After delay, SST varied
from 8:00 to
8:55
Sleep duration, bedtimes, rise
times
(weekdays and weekends), sleep-related
tardiness,
sleeping during class.
SST associated with percent of students
sleeping
≥8 hours/school night
(R2 = .8878, <50%
for
schools starting before 8:30, 66% for
school
starting at 8:55).
Wahlstrom et al. (2014) 61
2011–2013
Longitudinal
(before vs after
SST
change)
446 (pre-delay)
459 (post-delay)
Grades 9–12Jackson Hole,
Wyoming
Pre-delay: 7:35
Post-delay: 8:55
Sleep duration, bedtimes, rise
times
(weekdays and weekends).
Average school night sleep increased from 7.5h
to
8.2h. Average weekend sleep decreased from 9.3h
to
9.0h.
Wahlstrom et al. (2014) 61
2004–2013
Longitudinal
(before vs after
SST
change)
NRGrades 9–125 HS in Minnesota,
2 HS in
Colorado,
1 HS in Wyoming
Before delay, SST varied
from 7:30 to
7:50
After delay, SST varied
from 8:00 to 8:55
Attendance, academic performance,
car
crashes.
Most schools saw a decrease in tardiness and
an
increase in GPA. Two out of the four areas for
which
car crash data was available saw a major
decrease in car crashes
involving 16- to 18-year-old
drivers (≥65%). One
saw a small decrease (6%),
while another saw a small
increase (9%).
Paksarian et al. (2015) 71
2001–2004
Cross-sectional7216 (245 schools)13–18 yearsNationally (USA)
representative
Mean: 8:01
Range:
7:05–9:22
Weeknight bedtime, sleep
duration
(weeknight and weekend), weekend
compensatory
sleep
Later SST associated with later bedtime (10
minute
later bedtime for each 30 minute delay in
SST).
Later SST associated with longer sleep duration
for
SST before 8:01 only (11 minutes for each 30
minute
delay in SST). Difference only among boys
only and varied by
urbanicity. Sleep duration
increased for boys in major
metropolitan areas and
decreased for boys in nonurban counties.
SST not
associated with weekend compensatory sleep.
Only Abstracts Available
Allen and Mirabile (1989) 50
Not
specified
Cross-sectional61Grades 10–12
(Mean
age
17.1 years)
NREarly school: 7:30
Late school:
8:00
Sleep duration, bedtimes, rise
times
(weekdays and weekends).
Later SST corresponded to later rise times (p
<
.05), but no difference in bedtimes. Sleep
duration
difference not significantly different.
Allen (1992) 51
Not specified
Cross-sectional102Grade 12NREarly school: 7:40
Late schools:
8:30
Sleep duration, bedtimes, rise
times
(weekdays and weekends).
Earlier SST corresponded to shorter
weeknight
sleep duration (p < .035), more sleep problems
(p =
.04), and later weekend rise times (p = .03).
Carskadon et al. (1995) 53
1994
Longitudinal (before
vs after SST
change)
7Grade 9–10Rhode IslandLate (Grade 9): 8:25
Early (Grade 10):
7:20
Sleep duration, sleep start time,
sleep
offset time (measured with actigraphy)
Earlier SST (65 minutes) corresponded to
shorter
sleep duration (38 minutes, p < .02) due to
earlier
rise times (59 minutes, p < .005). No
significant
difference in school night sleep start time.
Kowalski and Allen 52
Not specified (1995)
Cross-sectional97 (early school)
119 (late
school)
Grades 11–12NREarly school: 7:20
Late school:
9:30
Sleep duration, bedtimes, rise
times
(weekdays and weekends).
Earlier SST corresponded to shorter
weeknight
sleep duration (p = .002).
Wolfson et al. (1995) 54
1994
Longitudinal (before
vs after SST
change)
15 (May have
included
students
in Carskadon et al. 53 )
Grade 9–10Rhode IslandLate (Grade 9): 8:25
Early (Grade 10):
7:20
Sleep duration, sleep start time,
sleep
efficiency (measured with
actigraphy);
emotional/behavioral problems from
Youth Self
Report (YSR) summary.
Earlier SST (65 minutes) corresponded to
shorter
sleep duration (39 minutes, p < .001).
No
significant difference in school night sleep start
time
or sleep efficiency. YSR total problems and
externalizing scores
decreased with earlier SST.
Open in a separate window

Abbreviations: ACT, originally American College Testing –
one of two standardized tests commonly used in college admissions in the
United States; HS, high school; MS, middle school; NR, not reported; SD,
standard deviation; SST, school start time.

Changing school start times is often a major endeavor that involves
coordination between school faculty and staff, transportation resources,
parents, students, and administration, and can take years to accomplish.
Cross-sectional studies can be conducted without having to wait for a school or
school district to undertake a change in school start time. However, as with all
cross- sectional studies, only associations between school start times and other
variables can be shown—not cause and effect. Other school
characteristics, such as socioeconomic status of students, can also have effects
on sleep and other outcomes but is often not reported.

In the longitudinal studies, data are collected on students and schools
before and after a change in start time. Some data that are regularly collected
by schools, such as attendance and grades, can be obtained retroactively by
researchers. Other data, such as those obtained from student sleep surveys, need
to be collected before the start time change is implemented, and including these
data can increase the duration of the study. Some studies evaluate
characteristics of the same students before and after the change. Others
evaluate the student population (either the entire school or specific grades in
school) before and after the change. This second method, for instance, could
compare outcomes in 9th-grade students in the year before the start time change
with the same outcomes in 9th-grade students in the year after the change. Both
of these methods have their drawbacks. Although it would seem to be preferable
to evaluate the same students before and after a change, individual students can
undergo significant changes from year to year that could exaggerate or diminish
the effect of changing start times. However, by being able to evaluate changes
in variables for individual students, researchers are able to address questions
such as, “Did the students who got more sleep after the start
time’s change have improved outcomes?” Although longitudinal
studies may provide stronger evidence of causation than cross-sectional studies
by addressing the issue of temporality, it is important to assess whether
appropriate control conditions are used, whether analyses account for covariates
(eg, age, sex, or socioeconomic status), and whether other explanatory variables
are considered (eg, implementation of graduated drivers licensing).

Sleep and Sleepiness

Since delaying school start times is primarily intended to address the
problem of insufficient sleep among adolescents, most of the studies focused on
the association between school start times and sleep variables. Not
surprisingly, students at schools with later start times got out of bed later on
school days than those at earlier starting schools. 35 , 36 , 50 , 53 , 55 , 56 , 60 , 62 – 69 The association between school
start times and bedtimes, however, was mixed. Of 19 studies that evaluated the
association between school start times and bedtime, there were no start
time-associated differences in weekday bedtimes in eleven studies. 35 , 50 , 53 – 55 , 60 , 62 , 67 , 68 , 70 However, six
studies observed a later bedtime among students in schools that started at later
times. 34 , 36 , 56 , 64 , 66 , 71 It should be noted that in the study by Wolfson and
colleagues, this bedtime difference was observed only in the autumn. 64 Two studies unexpectedly
reported earlier bedtimes after a delay in start times. 65 , 69 In the study by Owens et al., some students stated that
after seeing the benefits of getting more sleep with the delay in school start
times, they sought to further increase their sleep by going to bed
earlier. 65 In
Paksarian et al, bedtimes were delayed by only 10 minutes for each 30 minute
delay in school start times. 71
In 29 reports, a later start time was found to be associated with longer weekday
sleep duration, 34 , 36 , 38 , 51 – 56 , 60 – 79
including the studies that noted later bedtimes. 34 , 36 , 56 , 64 , 66 , 71 In contrast to the majority of
studies that observed longer sleep duration in later starting schools, two
studies comparing students from schools with different start times did not
observe a significant difference in sleep duration. 35 , 50 For
one of these, the difference in sleep duration did not meet the authors’
effect size criterion, although the difference would not have been expected to
be large since the difference in school start times was only 20
minutes. 35 The other
study observed longer sleep duration for students at the later starting school,
but the difference was not statistically significant. 50 Another study observed a significantly longer
sleep duration for 7th- and 8th-grade students of only one of two later-starting
districts. 60 Sleep
duration for the second later-starting district was also longer than for the
early-starting district, but the difference was not statistically
significant. 60
Paksarian et al. observed longer sleep durations with later school start times
(11 minutes for each 30 minute delay in school start times), but only for
schools that started before 8:01 AM. 71 In further analysis, the authors found the longer sleep
duration for boys only (20 minutes for each 30 minute delay in school start
times) and that there was variation by urbanicity, with an increase in sleep
duration for boys in major metropolitan areas and a decrease for boys in
nonurban counties. 71 The
authors suggested that the different association according to urbanicity may be
due to differences in mode of transportation to school and time spent traveling
to school, but they did not have data to investigate the possible role of
transportation in their study. Although nearly all the studies reviewed used
self-reported sleep data either from sleep diaries or survey questions, the two
studies that used data from electronic wrist monitors (actigraphs) worn during
sleep confirmed the general finding of longer weeknight sleep duration for
students with later start times. 62 , 70 Eleven of the
positive studies found that students got at least one additional minute of sleep
for every two minutes of difference in start time (eg, at least 30 minutes more
sleep when start time was one hour later), 34 , 55 , 56 , 60 , 61 , 64 , 65 , 68 , 70 , 72 , 78 although six
other studies observed smaller, yet statistically significant,
differences. 51 , 52 , 62 , 63 , 73 , 74

In addition to reporting longer sleep durations, students with later
start times were less likely to report daytime sleepiness or falling asleep in
class in nearly all studies that assessed these outcomes. 34 , 36 , 55 , 56 , 60 , 64 , 65 , 69 , 72 , 74 Two studies observed no
difference in sleepiness based on school start times. In the Norwegian
study, 78 start times
were delayed from 8:30 AM to 9:30 AM on Mondays only. The lack of association
could have been due to either the change being in effect only one day a week or
the earlier start time already being late enough. In the Croatian
study, 80 the students
at the earlier starting schools were predominantly boys, while girls made up
most of the population at the later starting schools. That study found that
girls had later chronotype (evening preference) and more sleepiness. In
addition, the schools in the Croatian study alternated their schedule weekly,
with schools starting in the morning one week and in the afternoon the next.
Even with a delay in start time, falling asleep during class appears to remain a
major problem, however. In Wahlstrom and colleagues’ survey of students
post-start time change, 27% reported falling asleep in a morning class
in the previous 2 weeks, and 29% fell asleep in an afternoon
class. 61

Other methods for assessing students’ degree of sleep-deficiency
were used in various studies. Students in a study by Carskadon and colleagues
underwent polysomnography (a type of sleep study that measures multiple factors
such as electrical activity in the brain, heart rate, movements of the eyelids
and legs, and respiratory airflow) and multiple sleep latency tests. 62 After an advance in start time
from 8:25 AM to 7:20 AM, students had a shorter REM sleep latency (time between
sleep onset and onset of REM sleep) on polysomnography and a shorter sleep
latency (time to sleep onset during a standard testing protocol). 62 Both of these results indicate
sleep-deficiency. Differences in sleep patterns between weeknights and weekend
nights can also indicate insufficient weeknight sleep as students try to make up
for lost sleep on the weekends. Seven reports that evaluated weekend sleep
patterns found more “catch-up” sleep on the weekends for earlier
start times, 51 , 61 , 64 , 66 , 69 , 74 , 78 although one found no
difference in this outcome. 71
One study assessed weeknight and weekend sleep and observed longer weeknight
sleep duration and no change in weekend sleep patterns after a delay in school
start time, which could be interpreted as a decrease in
“catch-up” sleep. 67 However, the difference between weeknight and weekend sleep
was not analyzed. Three studies that included information about daytime naps
noted that students with earlier school start times reported more
napping, 38 , 66 , 75 presumably in an attempt to make up for insufficient
nighttime sleep. Sleepy adolescents may also attempt to lessen sleepiness with
caffeine. One study asked students about caffeine consumption and observed that
caffeine use decreased after a 25 minute delay in school start time. 67

Academics and Cognition

An outcome of particular interest to school administrators, teachers,
and parents is academic performance; however, evaluating how delayed start times
affect school grades or academic performance is difficult for several reasons.
Class grading is not standardized and varies by subject, teacher, and school.
Standardized tests such as the Scholastic Aptitude Test or the ACT are not taken
by all students and are more likely to be taken by students planning to attend
college. Finally, students with very good academic performance before a delay in
school start time do not have much room for improvement. Given these
limitations, however, some evidence suggests a positive association between
later school start time and academic performance, 57 , 58 , 60 , 61 , 64 , 81 although the association may
be relatively weak 55 and not
universal. 59 , 67 , 80

The first cross-sectional school start time study by the University of
Minnesota found higher self-reported grades for students in later starting
schools. 60 Mean
self-reported grades for the two districts that started before 7:30 AM were 6.4
and 6.5 (on a scale from 1 = mostly F’s to 9 = mostly A’s)
compared to 7.1 for the district starting at 8:30 AM (p < .05). However,
the increase in grades observed from this group’s subsequent
longitudinal study was small and not statistically significant. 55 In their latest longitudinal
study including 8 schools, the same group noted that most schools saw an
increase in grade point average after delaying school start times. 61 Arlington Public Schools
(Arlington County, Virginia) observed an improvement in 10th grade
students’ 1st period grades after a 45 minute delay in high
school start times, with no change in 7th grade students’
1st period grades after a 20 minute advance in middle school
start times. 81
Hinrichs’ investigation into ACT scores and school start times in the
Minneapolis-St. Paul area, which included school districts that did not delay
school start times, controlled for various covariates and found no association
between school start times and ACT scores. 59 The annual ACT participation rate among Minnesota high
school graduates varied from 59% to 66% during the study period
(1993–2002). 59
Hinrichs also evaluated the association between school start times and
standardized test scores in Kansas (Kansas State Assessments) and the Virginia
suburbs of Washington DC. 59
Again, he found no association between school start times and academic
achievement in these analyses. 59 Wolfson and colleagues observed higher grades after
delaying school start times for 8th grade, although not for 7th-grade
students. 64 Another
study linked school start times and standardized test scores for middle school
students (grades 6–8) from 1999 to 2006 in the eighteenth largest public
school district in the United States. 57 In the cross-sectional component of that study, an hour
later start time corresponded to higher test scores on both math and reading (on
the order of 3 percentile points). 57 The longitudinal component of the same report looked at
schools that had changed school start times over the course of the study and
found that a one hour delay in start time corresponded to a 2 percentile
increase in math and 1.5 percentile increase in reading. 57 Among older students, U.S. Air
Force Academy freshmen, students assigned to a first period course and therefore
an earlier start to the school day had poorer grades. 58 A longitudinal study of nearly 200 boarding
school students did not see a change in self-reported grades after a 25 minute
delay in school start times. 67
In Milic et al.’s study in Croatia, students with an earlier school
start time performed better academically than students at the schools with later
start times. 80 However, in
addition to the difference in the make-up of the student populations (more boys
at earlier schools and more girls at later schools) in that study, students were
also aware of the school schedule at enrollment and the response rate was
low.

Several studies have investigated the association between school start
time and cognitive outcomes. Two studies found that students with later start
times reported fewer problems concentrating and paying attention. 70 , 72 In contrast, a study in Spain measured attention level
via a sustained attention task among students at three schools with different
start times (8:00, 8:15, and 8:30) and observed the highest average attention
level at the school starting at 8:15. 77 However, it should be noted that the mean inductive
reasoning score, a measure of intelligence which is positively associated with
attention, was significantly lower for the latest-starting school than the other
two schools. 77 The Norwegian
study that delayed start times on Mondays included reaction time tests and found
that students at the school with delayed start time had significantly fewer
lapses and faster reaction times on Monday than Friday compared to no difference
among students at the control (no delay) school. 78

Several studies asked students how much time they spent on homework.
There was no consistent association between school start time and homework time.
Wahlstrom and colleagues found that students with later school start times
reported less hours of homework, 60 whereas Edwards observed the reverse 57 and Boergers and colleagues
saw no difference. 67
Interpretation of these results in difficult. An increase in time doing homework
could indicate an improved ability to concentrate or less efficient studying.
Since the value of homework is hotly debated, this outcome should not be taken
out of context.

Attendance/Tardiness

School attendance is also important for academic success. A recent
report found that short sleep duration was strongly associated with odds of
school absences. 82 Several
studies included in this review found that earlier start times were also related
to more frequent tardiness and more absences. 55 , 57 , 60 , 61 , 64 , 65 In one study, even with
delaying start times from 8:00 AM to 8:55 AM, nearly a third of students
reported being late to class because of oversleeping in the 2 weeks before the
survey. 61 However, one
study of schools in the Minneapolis-St. Paul area found no association between
school start times and overall attendance rates. 59 The report by Arlington Public Schools stated
that “maturity, rather than starting time, has the biggest impact on
attendance rates.” 81
However, when comparing 10th graders before and after the delay in
high school start times, attendance rates were lower after the delay. Despite
this finding, academic performance improved for those students. The report also
noted that the attendance reporting procedures changed during the course of the
study.

Depression

Sleep is strongly linked with many psychiatric disorders, including
depression and anxiety. 83
Although sleep problems may be symptoms of mental health disorders such as
depression, there is also evidence of a causal relationship between insufficient
sleep and depression, as well as mood in general. 84 , 85 Due
to this observation, some school start time studies included depression symptoms
as part of their student assessments. Students at later-starting schools
appeared to experience fewer depression symptoms (lower depression
scores). 55 , 60 , 65 , 67 Incidentally,
shorter REM sleep latency, such as was observed by Carskadon and colleagues
after an advance in start time, 62 is also often observed in major depression. 86 One study found no difference
in students’ positive or negative affect with delayed school start
time. 78 However, in
that study, the start time was delayed on Mondays only.

Motor Vehicle Crashes

Four studies also investigated motor vehicle crashes among young drivers
(aged 18 years or younger) in areas served by schools with different start
times. In a Kentucky county, Danner and Phillips saw a 16.5% decrease (p
< .01) in motor vehicle crash rates for 17- and 18-year-old students in
the 2 years following a 1-hour delay in school start time by county high
schools. 74 During the
same time period, crash rates for this age group increased by 7.8% in
the rest of the state. 74 In
their 2011 report, Vorona and colleagues compared crash rates for teen drivers
aged 16 to 18 years in 2 neighboring, demographically similar cities (in eastern
Virginia) with different start times. In 2007 and 2008, the teen crash rates
were significantly higher in the city with an earlier school start
time. 87 For both
cities, teen crashes peaked during the morning commute time. 87 The group went on to perform
similar analyses for two adjacent counties in central Virginia with different
school start times. 88 During
the 2009–2010 school year, crash rates among 16–18 year olds
were higher (p < .05) in the county with the earlier school start
times. 88 The following
year, crash rates among 16–17 year olds were higher (p < .05) in
the same county, but difference was not statistically significant when 18 year
olds were included in comparison (p = 0.09). 88 Finally, Wahlstrom and colleagues investigated crash
rates among 16- to 18-year-old students in 4 areas near schools that underwent
delays in start time. Two areas saw major decreases (≥65%) in
teen crash rates after the delays, while one saw a small decrease (6%),
and another saw a small increase (9%). 61

Other Outcomes

There are a handful of other outcomes that have been reported by only
one study each. One study saw that students at schools with later start times
spent less time at work during the school week (p < .05). 60 More time working has been
linked to poorer academic performance. 89 However, the start time study was cross-sectional and
other variables such as socioeconomic status may explain the difference in time
spent at work. In the cross-sectional component of his study, Edwards found that
students at schools that started later reported less time watching
television. 57 When he
limited his analyses to schools that changed start times over the time course of
the study, he confirmed that students at schools that delayed their start times
reported significantly less time watching television. 57 Among 197 boarding school students, no change
in time spent in athletics or extracurricular activities was reported after a 25
minute delay in start time. 67
Finally, in a small study of 15 students who transitioned from grade 9 (school
start time 8:25) to grade 10 (school start time 7:20), self-reported conduct
problems and aggressive behaviors decreased with the change to an earlier start
time. 54 However,
within each grade, these behaviors were associated with shorter sleep duration,
which indicates that at least some of the decrease in these behaviors may be due
to maturation. 54

CONCLUSION

Delaying school start times for adolescents has been proposed as a policy
change to address insufficient sleep among adolescents, a largely sleep-deprived
population, and potentially to improve students’ academic performance,
reduce engagement in risk behaviors, and improve health. Nearly all studies to date
provide evidence that delaying school start time accomplishes the goal of increasing
sleep duration among these students, primarily by delaying rise times. Most of the
studies saw a significant increase in sleep duration even with relatively small
delays in start times of half an hour or so. Later school start times also generally
corresponded to improved attendance, less tardiness, less falling asleep in class,
fewer depression symptoms, and fewer motor vehicle crashes. Although not all studies
found that later start times corresponded to improved academic performance, no
studies found a negative impact of later school start times on academics.

IMPLICATIONS FOR SCHOOL HEALTH

In 2014, the American Academy of Pediatrics published a policy statement
urging middle and high schools to adjust start times to permit students to obtain
adequate sleep and improve physical and mental health, safety, academic performance,
and quality of life, and suggested that middle and high schools not start before
8:30 AM. 3 Schools and school
districts cannot make evidence-based policy decision without data. Therefore,
research results such as those presented in this review, as well as the recent
recommendations by the American Academy of Pediatrics, should be disseminated to
school districts, teachers, parents, and other stakeholders. The field still needs
rigorous research, including trials with controls, if possible. Many questions
remain, such as the issue of how late is late enough? Much of the focus has been on
high school students, but biological changes begin earlier, so further research into
middle-school students is warranted. More qualitative research about overcoming
obstacles to delaying school start times would also be valuable.

Schools contemplating a change in school start time may consider partnering
with researchers before a decision is even made. Baseline data on student sleep
characteristics, tardiness due to sleepiness, and prevalence of falling asleep
during class may be used in the initial decision of whether to delay school start
times. Parents and administrators may not realize the extent of the problem of
insufficient sleep among their students and this data may help persuade them that
some action is necessary. If school start times are delayed, everyone would benefit
from collection of detailed data before and after a time change. Not only would
other schools or school districts contemplating a change benefit from expanded
evidence, the district that undertook the start time change would be able to
evaluate the impact of the change and communicate their findings to their
stakeholders. Data collected should include not only sleep-related variables and
academic achievement measures, but also measures of mental health (such as
depression and anxiety symptoms), behavioral problems, risk behaviors, safety
statistics such as motor vehicle crash rates and pedestrian injuries, and
information on mode of transportation and travel time. Several obstacles to
implementing start time delays are often cited, including costs of changing bus
schedules, possible impact on athletics and extracurricular activities, and school
faculty and staff resistant to change. However, as recently reported by Owens et
al. 90 in their examination
of school districts that have delayed school start times, many anticipated problems
fail to materialize or are only temporary. Several school districts have seen
savings in transportation costs after changes made to facilitate delayed start
times. 90 Success stories
describing how districts creatively overcame obstacles to school start time changes
should be shared (for example http://www.startschoollater.net/success-stories.html ) to provide
ideas to other districts contemplating change.

Footnotes

Disclaimer: The findings and conclusions in this report are
those of the authors and do not necessarily represent the official position of
the Centers for Disease Control and Prevention.

Contributor Information

Anne G. Wheaton, Epidemiologist, Division of Population Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, 4770 Buford Hwy. NE, Mailstop F-78, Atlanta, GA 30341-3717, Phone: (770) 488-5362, Fax: (770) 488-5965, vog.cdc@9opi .

Daniel P. Chapman, Epidemiologist, Division of Population Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, 4770 Buford Hwy. NE, Mailstop F-78, Atlanta, GA 30341-3717, Phone: (770) 488-5463, vog.cdc@2cpd .

Janet B. Croft, Branch Chief, Epidemiology and Surveillance Branch, Division of Population Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, 4770 Buford Hwy. NE, Mailstop F-78, Atlanta, GA 30341-3717, Phone: (770) 488-2566, vog.cdc@0cbj .

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