1 The Science of Sleep and School Start Times Judith Owens MD MPH
Director of Sleep Medicine Boston Children’s Hospital Professor of Neurology Harvard Medical School
2 Myths and Misconceptions
Teens would go to sleep earlier if their parents just made them do it Some teens might need 9 hours of sleep, but mine does just fine with 6 (and so do I!) Take the cell phones (TV, laptops, tablets) away and kids will fall asleep If school starts later, they’ll just stay up later And if school lets out later, they’ll have to cram in the same amount of stuff in even less time Teens can just make up lost sleep by sleeping late on weekends or going to school later one day/wk Kids need to learn to get up early; that’s real life They’ll survive
3 “Two Process” Model of Sleep Regulation
Build Slide Homeostatic Sleep Drive (accumulation of adenosine + other somnogens) “Forbidden Zone” Alertness Level Sleep Sleep load → homeostat increases wake dissipates sleep Accumulates across day CR governed by SCN-light-dark OUTPUT ALERTING PULSE Sum = wake sleep propensity Direction of up down alertness MWT/MSLT = wake propensity “Circadian Nadir” Circadian Wake Drive (melatonin) 6 am 3 pm 9 pm 3 am 6 am Awake Asleep Now, imagine all of this shifting later by 2 hours…
4 Both Sleep Time and Sleep Timing are “Biological Imperatives”
In addition to a “master clock” in the brain, each cell in the body posses a “circadian oscillator”/ “clock” which must be synchronized with one another and the environment “Misalignment” between internal circadian clocks and the external light-dark cycle results in profound impairments in physiologic function and health Frontiers in Neurocience, 2013
5 Adolescent Sleep: The “Perfect Storm”?
*Includes middle and high school students
6 Sleep in Adolescents: Later Bedtimes
All adolescents experience a normal shift in circadian rhythms with age and in association with the onset of puberty This results in a biologically-based shift (delay) of up to several hours in both the natural fall sleep and morning wake times On a practical level, due to the “forbidden zone” this means that it’s almost impossible for the average adolescent to fall asleep much before 11pm on a regular basis Teens cannot “make” themselves fall asleep earlier
7 Sleep in Adolescents: Later Bedtimes
Environmental factors Competing priorities for sleep: homework, activities, after-school employment, “screen time”, social networking Circadian phase delay may be further exacerbated by evening light exposure Suppresses brain release of melatonin
8 Adolescents: Later Wake Times
These biological changes are in direct conflict with earlier high school start times (before 8:30am) because adolescents are biologically programmed to wake at 8am or later As a result, students are required to wake for the day and function during the “circadian nadir” (the lowest level of alertness during the 24 hour day) Early wake times also selectively rob teens of REM (rapid eye movement) sleep, which is critical for learning (of new information in particular) and memory
9 Adolescents: “Make-Up” Sleep
Increasing discrepancy between bed and wake times weekday/end Adequate compensation for sleep loss? Does not address compromised alertness on school days Does not reverse performance impairments
10 “Weekend Oversleep” Result: permanent state of “social jet lag”
Leads to “circadian misalignment” Exacerbation circadian phase delay Shift melatonin onset Prevents sufficient build-up of sleep drive Difficulty falling asleep Sunday night Result: permanent state of “social jet lag” Adjustment takes 1 day/time zone crossed Effects persist up to 3 days Associated daytime sleepiness, poor academic performance, depressed mood
12 Effects on Performance, Health and Safety
14 Impact on the Brain “Deficient” sleep (insufficient sleep for sleep needs and circadian mis-timing) negatively impacts: Cognitive function (decision-making, problem solving, planning, organization and other “executive functions”) Attention Memory Learning of new tasks Emotional regulation Risk-taking behaviors and misinterpretation of relative rewards/consequences
15 Neuroprotective Role of Sleep
Sleep loss affects neuronal functions Neuronal “plasticity”: ability of the brain to change structure/function in response to the environment Gene activation/expression Brain cell protection/repair from stress Recent research has found evidence of a “glympathic system” which eliminates toxins in the brain during sleep and allows the brain to have a “clean slate” from which to work
16 Impact on Health “Deficient” sleep (insufficient sleep for sleep needs and circadian mis-timing) is associated with: Risk of obesity Poor cardiovascular health Metabolic dysfunction (eg, type 2 diabetes) Depression and suicidal thoughts Alcohol and substance use
17 Impact on Safety Drowsy driving:
Drivers years are involved in more than 50% of the 100,000 police-reported fatigue-related traffic crashes each year 2015 survey of HS drivers in Fairfax County VA (SST 7:20am): 48% reported drowsy driving Prevalence 14% higher in students getting 8 Sleep loss impairments are equal or greater than those due to alcohol intoxication (ie, 3-4 beers) Lower use of seatbelts, bicycle helmets, increased texting and driving, drinking and driving
18 Impact on Safety Sleep loss is associated with an increased risk of pedestrian injuries in children Sleep loss is associated with increased sports-related injuries in high school students Sleep loss is associated with almost 3x risk in adolescents of work-related injury requiring medical care
19 Impact on Performance Academic performance GPA
Especially first period classes Standardized test scores Tardiness and attendance rates Graduation rates
20 AAP Recommendation: Delay School Start Time until 8:30 am or Later
Pediatrics 2014;134:
21 Brief History of School Start Times
BUT less than 1 in 5 middle and high schools in the US (N=40,000) start at the recommended 8:30am or later* In MA, average SST in 2015 for public middle and high schools was 7:37am (from 7:53am ) and only 2 schools (1%) of start at 8:30am or later* >80% start before 8am Students in earlier starting schools more likely to belong to an ethnic minority, be eligible for free lunches and have less educated parents *MMWR 2015
22 Outcomes: Sleep* Bedtimes remain the same or in some studies actually shift earlier Students obtain significantly more sleep More morning sleep The later the start time, the greater the sleep amounts But even a 30 minute delay results in improvements Students report less daytime sleepiness (falling asleep in class, doing homework) >8:30am the sleep and circadian “sweet spot”? *Wheaton AG et al. J School Health 2016 Review of 38 reports examining the association between school start times, sleep, and behavioral, health and academic outcomes among adolescent students
23 Outcomes: School Performance*
Attendance improves Tardiness rates drop Drop-out rates decline Standardized test scores improve In one study SAT scores for the top 10% of students increased by more than 200 points Grades improve 5/6 schools showed significant increase in GPA pre-post in English, math, science and SS Disadvantaged students may benefit more Larger effects of start times at lower end grade distribution** Effects of 1st period classes larger for black students*** *Wheaton AG et al 2016 **Edwards 2012 ***Cortes et al 2012
24 Outcomes: Health & Safety
Delayed SST are associated with improvements in: Mood (fewer report feeling unhappy, depressed) Health (decreased health center visits) Safety KY: 7:30 to 8:40a start time; teens involved in car crashes down by 16% (vs 9% increase in the rest of the state) VA: Adolescent crash rates VA Beach (7:20a) vs Chesapeake (8:40a) 40% higher and peak 1 hour earlier CDC study (2014): Reduction crash rates in 16-18yo by as much as 65-70% (MN, CO, WY) VA: SSTC (7: :10a) associated with 5% overall reduction MVA in teens, 9% reduction distraction-related crashes, 20% reduction alcohol-related crashes
25 Outcomes: $$$ RAND Corporation report (2017)*
Potential significant economic gains of a state-wide shift in start times to >8:30am related to improved academic performance of students resulting in increased lifetime earning potential and reduced car crashes Economic gain [modeled across 47 US states] estimated annual gain of ~ $9.3 billion Roughly the annual revenue of MLB *Hafner, Marco, Martin Stepanek and Wendy M. Troxel. Later school start times in the U.S.: An economic analysis.
26 Elementary School Start Times
Sleep needs: 9-12 hrs* Circadian preference (chronotype): owl vs lark** School, activities, electronic media, later bedtimes, earlier rise times, irregular sleep/wake schedules contribute to deficient sleep However, as opposed to adolescents, they are biologically, environmentally and socially more amenable to manipulation of bedtimes (ie, to move sleep onset earlier) if required Is there a sweet spot? Data is mixed but suggest 7:30-9am Earlier start times more impact on academics, behavior Issues of civil twilight, safety concerns Elementary-aged children need hours of sleep at night. Daytime sleepiness and naps are rare in this age group and are usually indicators of sleep issues. Circadian preferences for morning (larks) or evening type (owls) start to emerge in this age group. Homework, evening activities, and TV all contribute to sleep issues (later bedtimes, earlier rise times with morning school start time) Sleep problems occur in about 1/3 of elementary-school children (Owens et al., 2000; Sadeh et al., 2000). Parents are less aware of sleep problems so important to question children directly. *AASM 2016 **But most school-aged (pre-pubertal) children have a “morningness preference”
27 Lessons Learned District superintendent support and leadership critical School board involvement key School leadership (ie, principals) and teacher support vital Importance of middle/elementary school principal, teacher, parent involvement Importance of student engagement Critical role of community education Health, safety and academics Critical role of community engagement Identification and involvement of key stakeholders
28 Lessons Learned Critical to allow adequate time for families to become informed and make sufficient plans prior to implementation Each community faces different, unique challenges But you don’t have to “reinvent the wheel” Not all students will benefit equally The goal is to provide “the greatest good for the greatest number of students” Anticipation often worse than reality (impact on athletics, teacher retention, after-school programs, childcare issues) Initial challenges reduced over time
29 Thanks for your attention!
What is your vote? Thanks for your attention!
30 Elementary School Start Times: The “Flip”
Impact of School Start Time Changes: HS students delayed from 7:30am to 8:15am Students in grades 3-5 advanced from a start time of 8:20am to 7:45am HS students got 35 minutes more sleep 3rd graders also got more sleep (+24 minutes) after the change Sleep duration changes in 4-5th graders negligible No differences in behavior measures post-change Grade SST 1 BT/WT (SD HH:MM) SST 2 Sleep Duration Difference (Min) 3 8:37p/6:49a (10:11) 8:22p/6:57a (10:35) +24* 4 8:52p/6:56a (10:03) 8:22p/6:22a (9:59) -4 5 9:10p/6:59a (9:49) 8:43p/6:23a (9:40) -9 10 (7:42) (8:17) +35** Appleman et al. School start time changes and sleep patterns in elementary school students. Sleep Health, 1(2) (2015), *Largely accounted for by earlier bedtimes **Completely accounted for by later rise times; 0 min difference bedtimes