the biology of teen sleep patterns -...
TRANSCRIPT
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SPONSORED BY THE
Center for Applied Research and Educational Improvement in the College of Education and Human Development
The Biology of Teen Sleep Patterns
Mary A Carskadon, PhD
EP Bradley Hospital & Brown Medical School
Overview
• Adolescent sleep biology
• Sleep biology and early rising
• Sleep and the adolescent brain
• Consequences of too little sleep for teens
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Factors Affecting Sleep Patterns
• Behavior and circumstancese.g., life-style choices, socio-economic status,
health, employment, school
• Intrinsic biological processes– Sleep homeostatic system (sleep “pressure”)
– Circadian timing system
Observed features of the circadian system during adolescence
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Species Manifesting Juvenile Phase Delay
• Homo sapiens (humans)
• Macca mulatta (Rhesus monkeys)
• Octodon degus (degu) [some ?]
• Rattus norvegicus (laboratory rat)
• Mus musculus (laboratory mouse)
• Psammomys obesus (fat sand rat)
Hagenauer et al., Devel Neurosci, 2009
Chronotype and Adolescence
• Time of midsleep on “free” days
• Later timing is marked across the 2nd decade
Roenneberg et al., Current Biol., 2004
Late
Early
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Puberty and Melatonin Onset Phase: Hormonal Signal of Nighttime
19
20
21
22
23
Mel
aton
in O
nset
Tim
e
1 2 3 4 5
Tanner Stage
Carskadon et al. NYAS, 2004
11pm
8pm
10pm
9pm
7pm
What might underlie phase delay?
• Changes in light exposure
– Staying up later // more late light = delay
– Waking up later // less morning light = no advance
• Change in phase‐dependent sensitivity to light exposure
• Longer longer internal day length
• Diminished amplitude of the melatonin rhythm
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Exaggerated phase delay to light in pubertal female mice
Hagenauer et al., Devel Neurosci, 2001; after Weinert & Kompaeurova, Zoology, 1998
JuvenileAdult
Advance(earlier)
Delay(later)
0
2
4
6
8
23.6 23.8 24.0 24.2 24.5 24.7
Intrinsic Period
Adolescents
Adults
#
Human Intrinsic Circadian Period—Internal Day Length
Carskadon & Acebo Sleep, 2005
LongerShorter
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Adolescent Melatonin Amplitude
Crowley et al., Dev Psychobiol, 2011
Prepubertal
Postpubertal
Summary of Process C Changes
• Phase is delayed during adolescent development– Phase preference (chronotype) is later
– Melatonin phase is later
• Phase‐dependent light sensitivity may change
• Internal day is longer than in adults
• Amplitude of circadian nocturnal melatonin declines
• Result: late nights are favored (so, too, late mornings)
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Features of Adolescent Sleep‐Wake Homeostasis (Human)
Jenni & Carskadon Sleep, 2004
Slow wave sleep
Slow wave activity
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The adolescent brain changes
Density of neuronal connections, cerebral metabolic rate, and brain wave amplitude decline during adolescence
Feinberg et al., J Theor Biol.,1990
Cerebral metabolic rate
Cortical synaptic density
Delta wave amplitude
Sleep phenomenology changes; does sleep regulation?
Recovery process (dissipation)
Accumulation process
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Jenni, Achermann & Carskadon Sleep, 2005
7.7 h
13.5 h
3.0 h
2.9 h
td = 2.8 h td = 2.7 hDecay Time Constant
Tanner Stages 1/2 Tanner Stage 5
Sleep pressure dissipation does not change in adolescence
Across pubertal development, SWA accumulation rate slows down
Jenni, Achermann & Carskadon Sleep, 2005
7.7 h
13.5 h
3.0 h
2.9 h
td = 2.8 h td = 2.7 hDecay Time Constantti = 8.9 h ti = 12.1 hRise Time Constant
Tanner Stages 1/2 Tanner Stage 5
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Staying awake longer gets easier…up to a point.
Taylor et al., J Sleep Res, 2005
Hours Awake
2.5 6.5 10.5 14.5 18.5 22.5 26.5
Model of Process S in Development
Jenni & LeBourgeois Curr Op Psychiatry, 2006
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Summary of Process S Change
• Recovery sleep process does not change across adolescence
– Need for sleep is stable
• Accumulation of sleep pressure slows
– Staying awake longer is easier
• Result: late nights are easier to achieve, but the same amount of sleep is needed
Adolescent Sleep Behavior
• Bedtime becomes later
• Rise time becomes earlier (school dependent)
• Total amount of sleep is reduced
• Chronic insufficient sleep affects morning alertness most, especially when waking at an adverse circadian phase
• Evening alertness is bolstered by the clock‐dependent alerting signal
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Daytime sleep tendency in early‐rising high school students
• 10th grade
• Start time = 0720
• Sleeping about 7 hours a night
Carskadon et al. Sleep, 1998
0
5
10
15
20
Sle
ep L
aten
cy
(mea
n+se
min
utes
)
0830 1030 1230 1430
0
10
20
30
40
0830 1030 1230 1430
Per
cent
age
of T
ests
w
ith R
EM
Sle
ep
REM occurred in 12 of 25 subjects—most in the morning
REM sleep tendency also affected
Carskadon et al. Sleep, 1998
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Consequences of Clock/Homeostasis/Lifestyle Interaction
• Chronic insufficient sleep
• Variable sleep timing
– Social Jet Lag (á la Roenneberg, Curr Biol, 2012)
• Deficits in mood, learning, impulse control, etc.
• Excessive sleepiness & possible substance use
Why should we care about short sleep? Sleep’s role in achievement and learning
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Sleep Prepares for Learning
• Too little sleep impairs information acquisition
– Sleepiness
– Irritability
– Distractibility
– Inattention
– Motivation
• That is, ability to process input is diminished
Sleep Prepares for Performance
• Too little sleep impairs information retrieval
– Sleepiness
– Irritability
– Distractibility
– Inattention
– Motivation
• That is, ability to access learned information suffers
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Caffeine or other stimulants may help, but they cannot substitute for sleep, especially because…
Consolidation/stabilization/strengthening
Information acquisition
Information retrieval
Filtering
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Carskadon, Pediatr Clin North Am, 2011
© M.A. Carskadon
Carskadon, Pediatr Clin North Am, 2011
© M.A. Carskadon
Social Jet Lag
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AcknowledgementsCollaborators/FellowsRon Seifer, PhDChristine Acebo, PhDOskar G. Jenni, MDPeter Achermann, PhDLeila Tarokh, PhDEliza Van Reen, PhDKatherine Sharkey, MD, PhD
Research Assistants
Participants
Lab Staff
Summer Research Apprentices!
Funding SourcesMH52415 MH01358 MH58879AA13252 MH076969 Periodic Breathing Foundation