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Sleep science: Decoding drowsy driving

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A study published in The Journal of Pediatrics finds an association between a teen’s preference for evening or morning activities, coupled with nightly sleep duration, influences how awake they feel behind the wheel.

Each year, around Daylight Saving Time, we set our clocks forward and reprogram our bodies to adjust to spring. While most people welcome warmer days and lingering daylight, the time transition – and losing an hour of sleep – may leave some feeling jet lag.

For teens, the time transition is even more pronounced. Due to an adolescent’s developing body and a release of hormones to support growth and development, their biological clock is naturally set for late-evening bedtimes. Getting enough sleep is tough, especially with packed activity schedules and early-morning school start times.

A new study in The Journal of Pediatrics finds the impact of student sleep deprivation extends past feeling alert in class. Almost half of teen drivers surveyed – 205 out of 431 – from Fairfax County Public Schools reported driving drowsy at least once during the 2015 school year, the study period. Out of the 431-person sample, 63.1 percent of respondents reported driving several times a week. One-third of participants drove every day.

Helping teens feel alert behind the wheel is two-fold: Healthy school start times, those starting at 8:30 a.m. or later, help. Getting enough sleep is critical. The researchers also found that a student’s chronotype, or their preference for morning or evening activities, based on the Morningness-Eveningness Scale for Children, factor into drowsy driving:

  • Students with an evening chronotype, or preference for evening activities, coupled with shorter school-night sleep duration, were more likely to experience sleep-impaired driving.
  • Students with a morning chronotype, and who got at least eight hours of sleep, had the lowest prevalence of drowsy driving.
  • Compared with students who slept for at least eight hours on school nights, those who slept for less than seven hours had a 13.9 percent higher prevalence of drowsy driving.
  • The mean age of students surveyed was 16.9 years. The mean range of school-night sleep was seven hours.

Daniel Lewin, Ph.D., associate director of sleep medicine at Children’s National Health System, encourages schools to adopt later school start times, which Fairfax County Public Schools did, and he encourages students and families to assess their sleep patterns – focusing not just on sleep quantity but on sleep quality. His advice for families or students hesitant to change is to start small.

Try a seven-day challenge: Sleep on a regular schedule, sleep for recommended amounts of time, based on age-appropriate guidelines, cut out naps and eliminate late-afternoon caffeine intake.

Most children and families will start to notice the immediate benefits of getting a good night’s sleep, especially throughout the week: less daytime sleepiness, happier moods, improved eating habits and feeling more alert behind the wheel, which impacts driver safety – and not just for teen drivers but for parents, teachers and everyone on the road.

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Studying the impact of later school start times

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Teens have a biological preference to fall asleep later than younger children and adults, and wake up later, due to a delayed release of hormones that promote sleep. This timing coincides with puberty and makes it harder for middle and high school students to fall asleep early – regardless of 5 a.m. alarms and 7:17 a.m. school start times.

After studying this trend among nearly 1,000 seventh and eighth-grade students in 11 middle schools within a Mid-Atlantic school district, Daniel Lewin, Ph.D., a sleep medicine specialist, pediatric psychologist and associate director of the sleep medicine program at Children’s National Health System, coauthored and published research entitled “Later Start, Longer Sleep: Implications of Middle School Start Times” in the Journal of School Health, which outlines the benefits of delaying school start times.

The research team divided students into two groups: Close to 650 students attended eight late-starting middle schools, where school started at 8 a.m., while nearly 350 students attended early-starting middle schools, where school started at 7:23 a.m.

Students starting school 37 minutes later, despite going to bed 15 minutes later than peers attending an earlier-starting school, got 17 minutes more sleep each night and were more likely to report feeling wide awake during class. The researchers predicted this later-starting school model would translate to students getting an extra 75 minutes of sleep a week – roughly 51 hours of extra sleep each school year. These researchers find that every two minutes in delayed school start times results in one minute of additional sleep each night for children and teens.

Sleep Chart

Middle and high school students should get 8.5 to 10.5 hours of sleep each night, ideally between 9 p.m. and 8:30 a.m. for 12- to 15-year-olds and 10:30 p.m. and 9 a.m. for 16- to 18-year-olds.

The American Academy of Pediatrics (AAP) published similar research in their journal, Pediatrics, about the benefits of letting teens catch up on sleep, citing a reduced risk of students being overweight, getting into car accidents or suffering from depression as well as a greater likelihood of having better grades, higher test scores and a better quality of life. AAP recommends schools start at 8:30 a.m. or later to allow students to get 8.5 to 9.5 hours of sleep each night and issued a statement in 2014, entitled “School Start Times for Adolescents.”

Dr. Lewin continues to track these benefits and works with schools to implement the changes. He recently wrote an editorial, entitled “All the Clocks Are Ticking: Sleep Health and Metabolism,” for the Journal of Adolescent Health about the correlation between improved sleep health, mental and physical health and academic performance, explaining how circadian clocks, present on a cellular level, influence behavior and metabolism.

While pushing school start times back requires an immediate investment of rearranging travel routes, bell schedules and after-school activities, several school districts near Washington, D.C., from Virginia Beach to Fairfax County, are adopting this public health model.

An economic analysis conducted by the RAND Corporation finds that after two years, the benefits of reorganizing school start times outweigh the costs.