Overview
What is Going on with Sleep in
Adolescent Development…and
Why it is a Problem
Mary A. Carskadon, Ph.D.
Brown Medical School
E.P. Bradley Hospital
•! Adolescence & Puberty Defined
•! Sleep phenomenology
•! Sleep regulation
–! Process S (sleep homeostasis)
–! Process C (circadian rhythms
•! Lifestyles of the 21st century
•! Public policy
–! School start time example
What is adolescence?
•! Ages vary by culture
•! WHO: 10-19 years; 10 -14 = early
adolescence; 15-19 = late adolescence
What about puberty?
•! Time when the reproductive organs become
functional and the secondary sexual
characteristics appear
•! Tanner staging can be used to scale puberty
•! Tanner stage and age are highly correlated
•! In early adolescence, if girls show finding at a
younger age than boys, pubertal maturation
may be relevant
The central question
Why do
adolescents (once
such champion
sleepers, so eager
to start the day)
struggle to wake up
in the morning and
struggle against
going to sleep in
the evening?
Adolescent Brain Changes
•! Density of neuronal
connections, blood
glucose metabolism,
and brain wave
amplitude are stable in
adulthood
•! All decline during
adolescence…a lot!
!"#$"##%&'(#)*"+,+-'./0..011'
2,"#3,+4',5'%67-'!"#$%&'"()&*+,".11/'
The “look” of sleep changes
Change is Asymmetrical
@+,'5,,#'
8,,#'
8%+9:;'<'!%+=:%>9#-'?#-.-*&/%0)1"&2"3%4'&5-)%6-%,"7881'
8%+9:;'<'!%+=:%>9#-'9*%%/'"#'A+,==7'
Sleep phenomenology changes
across adolescence, but how
does sleep regulation change
developmentally and how does
this play out behaviorally?
Two-Process Model of Sleep Regulation
(Borbély, 1982)
!! Process
C:
Circadian Rhythm
!! Process
S: Sleep/
Wake Homeostasis
(sleep pressure)
B9+3C6D'<'E$;,+F%##-''G///'
Measures of Process S
Process S: Sleep Homeostasis
•! Slow-wave activity (SWA) in sleep
[quantitative: slow EEG waves]
K6,,A'@+,==*+,'
•! Slow wave (NREM stages 3+4) sleep
[qualitative: deep sleep]
•! Sleep propensity (speed of falling asleep)
8"F,'9I'L%D'
(F%4,'>9H#69%>,>'I+9F'9-$&*1'/%0)1"%J,+'B9+3C6D'
Changes of Slow Wave Sleep
and Slow Brain Waves of Sleep
Dynamics of Sleep Pressure:
Building Up and Letting Go
8%##,+'K5%4,='.0G'
5>'P'G7Q';'
5"'P'Q71';'
M,##"'<'!%+=:%>9#-'9*%%/,'G//N'
Speed of Falling Asleep
L,$%D'8"F,'!9#=5%#5'
S"=,'8"F,'!9#=5%#5'
8%##,+'K5%4,'O'
5>'P'G7R';'
5"'P'.G7.';'
M,##"-'E$;,+F%##'<'!%+=:%>9#'9*%%/-'G//O'
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
8%D69+',5'%67-'!"9*%%/":%5,"788;'
Circadian Regulation Changes:
Measures to Assess Process C
Phase Preference and
Adolescence
•! Phase preference—when do you prefer to
be active, sleeping, etc?
•! Phase of circadian rhythms—what time is
it in your brain?
•! Period of the circadian timing system—
what is the internal day length?
•! Phase response to light—does light work
the same in adolescents?
•! Time of midsleep on
“free” days
•! European sample
•! Developmental
changes occurred at
a younger age in girls
than boys
S9,##,3,+4-'<4''%6="()&*+-'G//N'
•!
•!
•!
•!
•!
•!
Homo sapiens (humans)
Macca mulatta (Rhesus monkeys)
Octodon degus (degu)
Rattus norvegicus (laboratory rat)
Mus musculus (laboratory mouse)
Psammomys obesus (fat sand rat)
Melatonin Phase and
Puberty in Humans
Melatonin Onset Time
Animals with Adolescent
Phase Delay
23
22
21
20
19
1
2
3
4
Tanner Stage
T%4,#%*,+',5'%67-'>%?%*"3%4'&5-)-'G//1'
!%+=:%>9#'<'E$,39'3@A9-'G//N'
5
Activity offset delays in pubertal
Macaques
•! Puberty: phase delay
in the daily offset of
activity
•! If puberty is inhibited
by zinc deprivation,
the phase delay does
not occur.
Internal Day Length in Humans
8
Adults
6
Adolescents
# 4
2
0
23.6 23.8 24.0 24.2 24.5 24.7
Intrinsic Period
U96*3',5'%67-'(#V''A0&*%5-%6="0%?%*&/B%6=C,'G//G'
Exaggerated phase delay to light in
pubertal female mice
!%+=:%>9#'<'E$,39-'9*%%/"WE@KKX'G//O'
Circadian Rhythms Summary
•! Phase delays during adolescence
–! Phase preference is later
–! Melatonin phase is later
•! Intrinsic period may lengthen
•! Phase-dependent light sensitivity may
change
•! Result: late nights
T%4,#%*,+',5'%67-'>%?%*"3%4'&5-)-'G//1Y'%J,+'Z,"#,+5'<'[9FA%,*+9\%-'D&&*&E.-'.11Q'
Other factors co-opt the biology…
Academic obligations
Social opportunities
Substance use, including caffeine
Psychological stressors
Societal messages
Stimulating activities (“screens”) in the
evening
•! Parental control vs. autonomy (Gangwisch et
al., Sleep, 2010)
•! School start time
Bottom Line for Sleep
•!
•!
•!
•!
•!
•!
Nonschool
Nights
School
Nights
6
7
8
9
10
11
12
]K2'9*%%/")6"AB%')-1"F&**-'G//^'
School Start Time
_E'`+,%6a6"I,b',c%FA6,'
15;'U+%>,'
./5;'U+%>,'
QVGO'%F'
RVG/'%F'
!%+=:%>9#',5'%67-'.11Q'
Measured sleepiness
in high school students
@,+$,#5%4,'9I'8,=5=''
H"5;'S?g'K6,,A'
'
.O'
./'
O'
/'
/Qf/' ./f/'.Gf/'.Nf/'
'
'
K6,,A'd%5,#$D'
WF,%#e=,'F"#*5,=X
•! 10th grade
•! Start time = 0720
•! No schedule
manipulation
•! Sleeping about 7
hours a night
REM tendency also affected
G/
S?g'9$$*++,>'"#'.G'9I'GO''
=*3h,$5=_F9=5'"#'5;,''
F9+#"#4'
N/'
f/'
G/'
./'
/'
/Qf/' ./f/' .Gf/' .Nf/'
'
W!%+=:%>9#',5'%67'9*%%/-'.11QX
'
!%+=:%>9#',5'%67'9*%%/-'.11Q
Consequences of
Insufficient & Ill-timed Sleep
Summary
•!
•!
•!
•!
•!
Long days
Slower build-up of sleep pressure
Later circadian phase
Early school start time
Same “need” for sleep/sleep recovery
•! Too little sleep, waking up at the wrong time,
resulting in excessive sleepiness and other
waking consequences.
•!
•!
•!
•!
•!
•!
Excessive sleepiness
Impaired learning
Impaired behavior regulation
Increased risk taking
Poor mood, depression
Appetite and metabolic changes; possible
association with weight gain, obesity,
diabetes risk
•! Stimulant use