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Adolescents and Sleep

Adolescents and Sleep. The Circadian Cycle of Sleep. Virtually all plants and animals (even bacteria) adjust their physiology and behavior to the 24-hour day-night cycle under the governance of circadian clocks.

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Adolescents and Sleep

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  1. Adolescents and Sleep

  2. The Circadian Cycle of Sleep • Virtually all plants and animals (even bacteria) adjust their physiology and behavior to the 24-hour day-night cycle under the governance of circadian clocks. • Molecular biological studies have now revealed much about the genes and proteins that make up the machinery of these clocks • PER1,2 and 3, CLOCK, BMAL1, CRY • They are highly conserved across species, evidence that they have been preserved throughout evolution. • This circadian clock is intrinsic and adjusting it to local day/night cues is called “photoentrainment.” • This goes out of whack when we travel, causing “jet lag”

  3. The Cycle Persists, Even With No External Cues Humans (and many other animals) have an internal “clock” that continues to operate in the absence of any external information about the time of day; under these conditions, the clock is said to be “free running.” Rhythm of waking (blue lines) and sleeping (red lines) of a volunteer in an isolation chamber with and without cues about the day-night cycle. The subject awakened later each day and gradually shifted to a 28h sleep cycle. From After Aschoff, 1965, reproduced in Schmidt et. al., 1983.)

  4. The Suprachiasmatic Nucleus (SCN) is the Master Regulator of the Sleep/Wake Cycle

  5. The Neuroendocrinology of Sleep • Special light receptors in the retina project to the SCN. These help “photoentrain” sleep cues. • Projections from the SCN extend throughout the brain. • One set enters the pineal gland which makes the hormone melatonin. This hormone lowers body temperature and induces sleepiness.

  6. Teens Cortisol (the “waking” hormone) also right shifts. Cortisol release is under the influence of sex hormones.

  7. Sleep is Not Homogeneous • Sleep is composed of a succession of cycles, progressing from light to heavy. • The duration of the cycle remains constant throughout the night but the composition changes. • Composition also changes with age. • Age affects HOW and WHEN we sleep.

  8. Certain hormones and chemicals are released into the body as sleep progresses, growth hormones is one of them. • Teenagers need more stage four sleep than adults. • Stage four sleep may disappear by age 70. • Stage 4 sleep gets shorter as sleep progresses, and may only occur within a few hours of sleep onset. • REM occurs as we emerge from stage 2 back to stage 1. • During a normal healthy night’s sleep a person experiences four to five cycles of REM and non- REM sleep.

  9. The Importance of REM Sleep • REM sleep is physiologically distinct from all other types of sleep. • The brain is just as active in REM sleep as it is while awake. • Newborn sleep is upwards of 80% REM sleep. • Dreaming occurs in REM. • REM cycles are longest as dawn approaches. • Sleep deprived patients get to REM sleep faster (at the expense of stage 4). • Loss of REM sleep impairs survival in mammals and birds and can lead to behavioral or psychological disorders.

  10. Functional Role of REM Sleep • Memory consolidation, particularly procedural and spatial memory • Enhancement of REM sleep (with drugs) also enhances memory. • However…..humans with REM disorders are not memory impaired (the brain may be compensating). • Ontogenetic (Active) Sleep Hypothesis • Critical for brain development and maturation • Making new connections or “pruning” – plasticity • Babies deprived of sleep have behavioral disorders, smaller brains, sleep disorders and lower IQs • Adolescence is a major “critical period” for brain organization, particularly in the prefrontal cortex • It’s the “finishing school” for empathy, impulse control, and social reasoning

  11. Age Also Affects WHEN We Sleep Newborns sleep equal amounts in the day and the night then gradually shift to exclusive night time sleep (no naps) by age 5 or 6).

  12. Adolescent Shift in Sleep Patterns • Adolescents naturally stay up later and have a harder time falling asleep then children. • Termed an “evening chronotype” resulting from a delay in circadian phase • Accompanied by a later drop in melatonin • Typically starts after pubertal onset • A 2000 poll by the National Sleep Foundation found that over 45% of adolescents in the United States obtain inadequate sleep • National Sleep Foundation Sleep and Teens Task Force Adolescent Sleep Needs and Patterns: Research Report and Resource Guide. Washington: National Sleep Foundation; 2000. pp. 1–26. On the Wiki

  13. Sleep habits among teens have not changed much in the past 20 years. • School start time was the #1 predictor of wake time on school days. • Sociodemographic factors more heavily influenced bed time. • For each hour later school starts, teens get 25-45 min of extra sleep. Knutson et al. (2009) J Pediatr

  14. From: DevNeurosci. 2009 June; 31(4): 276–284.

  15. Why a Shift at Puberty? • Circadian regulation and reproduction are inextricably linked. • Many animals (not humans) are seasonal. • The SCN-Pineal system “senses” season and puts animals in torpor in winter. Animals do not reproduce during this time. • This can be prevented or reversed in the lab by keeping animals on “long day” light cycles. • This relationship goes both ways • Reproductive hormones affect sleep cycles and sleep cycles can affect hormone secretion. • Pubertal teenagers are, in so many ways, “hormonal.” • For women this reverses at menopause – and is accompanied by all kinds of sleep disturbances. • We all accept that babies “need” to sleep. This “need” comes back at puberty because it’s another critical period for brain development.

  16. How Much is Enough? • The National Center on Sleep Disorders Research at the National Institutes of Health recommends at least 9 hours a day for individuals under the age of 21 (8 for adults). • On average, studies have found that sixth-graders are sleeping an average of 8.4 hours on school nights and 12th-graders just 6.9 hours. • This means that high-schoolers are experiencing, on average, chronic sleep deprivation of 2 hours.

  17. Biology –vs- Environment • There is growing evidence that interacting with technology at night (particularly light producing toys like computers and phones, keeps teen up later…….BUT….. • Social factors cannot completely account for the adolescent delayed sleep onset • In well-rested human subjects, adolescents showed a decreased propensity to fall asleep in the evening hours • Taylor DJ, Jenni OG, Acebo C, Carskadon MA. Sleep tendency during extended wakefulness: insights into adolescent sleep regulation and behavior. J Sleep Res. 2005;14:239–244. • The shift is cross cultural (pre-industrial and modern societies) • The shift ranges from 1-4 hours with the peak occurring before age 20 • Girls begin to transition to a later chronotype a year earlier than boys and peak earlier than boys (about age 19) • The shift is typically longer in boys (closer to 4 hours)

  18. Are Teens Getting Enough Sleep? • According to a 2010 poll conducted by the National Sleep Foundation (1600 participants): • 28 percent of high-school students said they fell asleep in class at least once a week. In addition, 22 percent dozed off doing homework and 14 percent arrive late or miss school because they oversleep. • Four-fifths of students who get the recommended amount of sleep are achieving As and Bs in school; those who get less sleep are more likely to get lower grades. • Some 28 percent of adolescents say they are too tired to exercise. • Just 20 percent of adolescents said they get nine hours of sleep on school nights and 45 percent reported sleeping less than eight hours.

  19. Sleep Deprivation Has Costs • Linked to mood disorders • Depression, anxiety, suicidal thoughts, aggression, irritability • Poor school performance • Decreased participation in sports • Emotional problems (depression) • Increased risk of substance abuse • Nicotine and alcohol most common – both stimulants • May be self medicating to stay awake, deal with mood effects associated with sleep deprivation, or “poor choices” resulting from abnormal development of impulse control. • Disruption of glucose regulation • Increased risk of diabetes • Higher blood pressure • Overeating • Traffic Accidents

  20. Impact of Later School Start Timeon Teenage Driving Dec 15, 2008 (J. Clinical Sleep Medicine) Fayette County school start times adjusted to 1 hr later rest of KY public schools unchanged data compared Fayette county accidents/1000 students to other counties in state over 2 years Fayette County decreased 16.5%, while remainder of state increased 7.8%

  21. More Evidence…. • Presented at Annual Mtg American Academy of Sleep Medicine 2010 • Virginia Beach,Va start time 7:20 am, Chesapeake, Va start time 8:40 am(adjacent cities with similar demographics) • Chesapeake had 46.2 crashes/1000 teen drivers, Va Beach 65.4 crashes/1000 teens (41% difference)

  22. Delayed School Start is Not a New Idea • 1999: House Congressional Resolution 135 or the "ZZZ's to A’s" Act encourages individual schools and school districts all over the country to move school start times to no earlier than 8:30 a.m. • A few states have considered legislating start times to no earlier than 8:30. • 2001: National Institute for Mental Health (NIMH) made adolescent sleep part of its “Blueprint for Change.” • 10% of adolescents have an emotional or mood disorder that interferes with school and other activities • NIMH believes that sleep deprivation is a significant causal or contributing factor.

  23. 1997-1999 Minneapolis Public Schools (evaluation performed in 2000) -7 high schools changed start times from 7:15 to 8:40 am while 1 changed from 7:15-8:30 (Edina) -Sleep gain reported as avg1 hr/night -Attendance increased (83% to 87%) -Graduation rates improved -Subjectively, less fights at school, “easier to live with” at home. -Data on school performance (grades) difficult to extract due to variables (I.e. changed curriculum) “Sleep begets sleep”– kids felt so much better with 15-20 minutes extra, it encouraged them to sleep more, so gain increased with time. The Most Comprehensive Study to Date

  24. Subsequent Studies • 2007 Journal of Behavioral Sleep Medicine (Wolfson, et al.) • -urban NE MIDDLE schools with 7:15am vs 8:37am start times (similar socioeconomic class/demographics/race) • -N=205 (123 girls, 82 boys), 7th & 8th graders • -later school reported 37 min more total sleep despite 22 min avg later bedtime • -second analysis showed 65 more minutes sleep • -7th graders showed no difference in academic performance. 8th graders had stat. significantly higher avg grades than peers • -Earlier starting school 4x more often tardy • Mean time for onset of sleep was 11pm. *This is the only study available on middle school students.

  25. Data From a Situation Most Like Ours • Judith A. Owens, MD, MPH; Katherine Belon, BA; Patricia Moss, PhD Arch PediatrAdolesc Med. 2010;164(7):608-614. • Independent school in RI changed from 8 to 8:30). -Grades 9-12 • mean sleep duration: + 45 minutes • Those getting <7hr sleep decreased 79%, those reporting >8 hr sleep increased 16.4% to 54.7% • Subjective depression decreased 65.8%-45% • Subjective irritability decreased 84% to 62.6% • Subjective sleepiness during the day decreased from 69.1% to 33% • Class attendance increased 45% • Health center visits decreased from 15.3% to 4.6% On the Wiki

  26. A Study Showing No Benefit…. • 2002 Journal ofSleep and Breathing (Elliasson) • -plotted reported “total sleep time” versus GPA of 1200 middle/high school students (no adjustment to start time at school) • -found no correlation between amt of total sleep and school GPA • Questions significance of wake time versus total sleep duration.

  27. Summary • “ZZZ’s to A's” initiative states that since schools began to adjust start times more than 10 years ago, over 50 schools have adjusted start time and no school can be found which has reverted back to previous (later) schedule. • Data reported by National Sleep foundation

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