Megan Brooks

June 21, 2016

DENVER — Similar to their peers in high school, middle school students benefit from later school start times, new research suggests.

The study found that seventh and eighth graders reported significantly longer sleep duration, later bed times, and decreased daytime sleepiness when starting class around 8:00 am, rather than earlier.

Many studies have shown the benefits of later start times in high school students, but this is "one of only a few studies of middle school students (seventh and eighth graders)," senior author Danny Lewin, PhD, associate director of sleep medicine at Children's National Health System, Washington, DC, told Medscape Medical News.

"The study is unique because it is prospective and leverages an existing difference in school start times in two groups of seventh and eighth graders," Dr Lewin added.

Lead author Deborah Temkin, PhD, from Child Trends, Bethesda, Maryland, presented the study here at SLEEP 2016: 30th Anniversary Meeting of the Associated Professional Sleep Societies.

Physical and Mental Health Benefits

Drawing on newly collected student and parent survey data (969 surveys), the researchers used Inverse Probability of Treatment Weighted regression analysis to generate estimates of the relationship between school start time and sleep and sleepiness variables, factoring in grade, age, race and ethnicity, sex, home language, family structure, and parent education. Individual school start times varied between 7:20 and 8:15 am.

The researchers found that seventh and eighth grade students attending schools starting around 8:00 am get an average of 17 minutes more sleep per weeknight (actual mean, 8.39 hours) than their peers attending schools starting around 7:20 am (actual mean, 8.15 hours), despite their going to bed later on average (10:04 vs 9:31 pm).

Therefore, students attending schools with later start times get about an extra hour and 25 minutes sleep per school week, the authors note.

The students with later school start times went to bed about 6 minutes later than those with early start times. "This demonstrates a shift in the timing of the sleep phase, with the late-start group sleeping later in the morning. The slightly later bed- and wake-time are considered to be optimal for this age group, which is believed to convey both physical and mental health benefits," Dr Lewin told Medscape Medical News.

Students with later start times were less likely to report daytime sleepiness during the week than students with earlier start times (43% of late starters vs 35% of early starters reported being "wide awake").

Time spent sleeping on weekends was similar in the two groups (actual combined mean, 10.13 hours). "Longer sleep for both groups on the weekends (~10 hours vs an overall average of 8 hours) suggest that catch-up sleep is needed as a result of inadequate sleep during the week," Dr Lewin noted.

"These findings," he said, "add to a large body of literature demonstrating that later school start times are associated with improved sleep health. This study also suggests that middle school students benefit from later school start times, and school districts, state boards of education and federal policymakers should consider both high school and middle school students when they make recommendations about school start times."

Saul Rothenberg, PhD, from the Sleep Center at Greenwich Hospital, Connecticut, who was not involved in the study, is not surprised that middle school students benefit from later start times.

"It just adds to the idea that biological rhythms are really important and that they are part of life even in young children. That's an important demonstration," he told Medscape Medical News.

Support for the study was provided by a grant from the Robert Wood Johnson Foundation. The authors have disclosed no relevant financial relationships.

SLEEP 2016: 30th Anniversary Meeting of the Associated Professional Sleep Societies: Abstract 0947. Presented June 13, 2016.

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