Abstract
Objectives
High school start times are a key contributor to insufficient sleep. This study investigated
associations of high school start times with bedtime, wake time, and time in bed among
urban teenagers.
Design
Daily-diary study nested within the prospective Fragile Families and Child Wellbeing
Study.
Setting
Twenty US cities.
Participants
Four hundred thirteen teenagers who completed ≥1 daily diary report on a school day.
Measurements
Participating teens were asked to complete daily diaries for 7 consecutive days. School-day
daily diaries (3.8 ± 1.6 entries per person) were used in analyses (N = 1555 school days). High school start time, the main predictor, was categorized as
7:00-7:29 am (15%), 7:30-7:59 am (22%), 8:00-8:29 am (35%), and 8:30 am or later (28%). Multilevel modeling examined the associations of school start times
with bedtime, wake time, and time in bed. Models adjusted for age, sex, race/ethnicity,
household income, caregiver's education, and school type.
Results
Teens with the earliest high school start times (7:00-7:29 am) obtained 46 minutes less time in bed on average compared with teens with high school
start times at 8:30 am or later (P < .001). Teens exhibited a dose-response relationship between earlier school start times
and shorter time in bed, primarily due to earlier wake times (P < .05). Start times after 8:30 am were associated with increased time in bed, extending morning sleep by 27-57 minutes
(P < .05) when compared with teens with earlier school start times.
Conclusion
Later school start times are associated with later wake times in our large, diverse
sample. Teens starting school at 8:30 am or later are the only group with an average time in bed permitting 8 hours of sleep,
the minimum recommended by expert consensus for health and well-being.
Keywords
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Article Info
Publication History
Published online: October 16, 2017
Accepted:
September 9,
2017
Received in revised form:
August 20,
2017
Received:
June 23,
2017
Identification
Copyright
© 2017 National Sleep Foundation. Published by Elsevier Inc. All rights reserved.
