Summary: A slightly later start time for school could mean teens are able to get the amount of sleep their bodies need, researchers report.
Source: Penn State.
A later school start time could mean teens are more likely to get adequate amounts of sleep, according to Penn State researchers.
In a national study of urban teenagers, researchers found that high school start times after 8:30 a.m. increased the likelihood that teens obtained the minimum recommended amount of sleep, benefiting their overall health and well being.
“Teens starting school at 8:30 a.m. or later were the only group with an average time in bed permitting eight hours of sleep, the minimum recommended by expert consensus,” said lead author Orfeu Buxton, associate professor of biobehavioral health at Penn State. “Later school start times were associated with later wake times in our large, diverse sample.”
Buxton and colleagues report their findings Dec. 1 in Sleep Health, the Journal of the National Sleep Foundation, which devoted an entire special issue to the topic.
Teens with the earliest high school start times — 7:00-7:29 a.m. — obtained 46 minutes less time in bed on average compared with teens with high school start times at 8:30 a.m. or later.
School start times after 8:30 a.m. were associated with increased time in bed, extending morning sleep by 27-57 minutes compared to those teens with earlier school start times.
A common argument against later school start times is an assumption that teens will just stay up later.
“The presumption is if you let kids start school later they will simply go to sleep later and still not get enough sleep,” Buxton said. “But that’s a hypothetical scenario. There wasn’t data to back that up.”
While researchers did find that teens with the earliest school start times were going to bed earlier than those with 8:30 a.m. or later, the teens with earlier start times still did not get the recommended amount of sleep. Only those teens with schools that had a start time of 8:30 a.m. or later actually got the recommended amount of sleep, Buxton said.
One theory is that, despite going to bed earlier than their peers, teens with the earliest school start times didn’t get enough sleep possibly due to anticipation of an early wake time the following morning, according to Buxton.
In addition, the investigators considered other research that looked at teens’ “sleep debt,” where teens make up for lost sleep on non-school days, leading them to wake up consistently and significantly later than those on school days.
Both anticipation and sleep debt can misalign teens’ circadian clocks from expected early wake timing on school days, interfering with having consistent sleep.
Four hundred and thirteen teenagers completed an online daily diary each evening, beginning after 7 p.m., during seven consecutive days, including school days and non-school days during both the academic year and the summer, which was defined as September through May and June through August, respectively.
From each diary entry, researchers looked at the participants’ reports of the previous night’s bedtime, the time the teen woke up in the morning, whether or not the teen went to school, and the school start times.
Data collection included daily diary data from a subsample of the parent study, the Fragile Families and Child Wellbeing Study, which follows a longitudinal birth cohort of children born between 1998 and 2000 in 20 United States cities.
Co-authors include Anne-Marie Chang, assistant professor; Soomi Lee, assistant research professor; Nicole Nahmod, human research technologist all in biobehavioral health, Penn State; and Lauren Hale, professor of Family, Population and Preventative Medicine at Stony Brook Medicine in New York.
Funding: The research was supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health, as well as a consortium of private foundations.
Source: Marjorie S. Miller – Penn State
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Original Research: Full open access research for “High school start times after 8:30 am are associated with later wake times and longer time in bed among teens in a national urban cohort study” by Nicole G. Nahmod, Soomi Lee, Orfeu M. Buxton, Anne-Marie Chang, Lauren Hale in Sleep Health. Published online October 16 2017 doi:10.1016/j.sleh.2017.09.004
High school start times after 8:30 am are associated with later wake times and longer time in bed among teens in a national urban cohort study
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.
Daily-diary study nested within the prospective Fragile Families and Child Wellbeing Study.
Twenty US cities.
Four hundred thirteen teenagers who completed ≥1 daily diary report on a school day.
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.
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.
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.
“High school start times after 8:30 am are associated with later wake times and longer time in bed among teens in a national urban cohort study” by Nicole G. Nahmod, Soomi Lee, Orfeu M. Buxton, Anne-Marie Chang, Lauren Hale in Sleep Health. Published online October 16 2017 doi:10.1016/j.sleh.2017.09.004