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AASMMembershipSectionsNewsletter
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Issue #5
remainunclear. Burgess sought to investigatewhether evening
light exposure,when controlling for sleepdeprivation,would
reduce circadianphase advances tomorningbright light.Using
awithin-subjects design, 12 subjectswere assessedusing a3-day
phase-advancingprotocol for each sleep condition. Subjects either
obtained a9-hnighttime sleepopportunity, or a3-hdaytimenap
followedby a6-hnighttime sleepopportunity. Eleven subjects
showed reducedphase advances during the 6-hnighttime sleep
opportunity,with eight of the subjects obtaining similar amounts
of sleep independent of condition (1.7versus 0.7h, P<0.05).
Thesefindings suggest that the reduction inphase advances during
a shortenednighttime sleepopportunitymaybedue in a greater
extent to the additional ambient light proceeding thenighttime sleep
opportunity. (TB)
Combinationof light andmelatonin time cues forphase
advancing thehuman circadian clock.
Burke,T.M.,Markwald,R.R.,Chinoy, E.D., Snider, J.A.,
Bessman, S.C., Jung,C.M., et al. (2013). SLEEP, 36(11), 1617-
1624.
Thefindings from this study indicate that the combinationof bright
light exposure in the earlymorning and exogenousmelatonin in
the eveningprovide the greatest phase shift (advance) treatment
response. The results of the studywill hopefully encourageother
large trials infield settings (i.e., outsideof the controlled laboratory),
such that the results canbedirectly applied to the clinical setting.
(RRA)
Circadianphaseand its relationship tonighttime sleep
in toddlers.
LeBourgeois,M.K.,Carskadon,M.A.,Akacem, L.D., Simpkin,
C.T.,Wright,K. P., Jr.,Achermann, P., et al. (2013). JBiol
Rhythms, 28(5), 322-331.
This studymeasured circadianphaseposition andphase angle
betweendim lightmelatoninonset (DLMO) and sleep in45healthy
toddlers aged30 to36months.AverageDLMOwas 1929±0051h,
averagebedtimewas 2015±0036h, and average sleeponset time
was 2043±0043h. DLMO timewas correlated significantlywith
bedtime, sleeponset time, andwake time. Large inter-individual
variabilitywas observed amongparticipants. This study is thefirst
todescribe the fundamental properties of the circadian system in
2-3year old children, including timingofmelatoninonset and its
relationship tonighttime sleep. Thus, this study represents amajor
advance inour understandingof developmental aspects of circadian
rhythms inhealthy children. Thesenormativedatawill alsobe
helpful for interpretingdata inyoungpatients presentingwith
circadian rhythm sleep-wakedisorders. (KMS)
GeneticsandMolecular Clocks
Homeostaticand circadian contribution toEEGand
molecular statevariables of sleep regulation.
Curie,T.,Mongrain,V.,Dorsaz, S.,Mang,G.M., Emmenegger,Y.,
&Franken, P. (2013). SLEEP, 36(3), 311-323.
Agrowingbodyof evidence suggests abidirectional relationship
between circadian clockgenes and sleephomeostasis,with the
homeostatic regulationof sleep affectedby and affecting clockgenes.
Curie and colleagues investigated this relationshipby evaluating
clockgene expressionduring6hour episodes of sleepdeprivation
at different times of day indifferent strains ofmice. In addition, the
homeostatic sleepmarkers, deltapower andHomer 1a expression,
were also evaluated at different times of day. Their findings showed
thatmRNA levels of the clockgenePer2 increased and clock
controlledgeneDbpdecreasedwith sleepdeprivation, exceptwhen
sleepdeprivationwas conducted at ZT12-18, thus demonstrating
sleep-wake and timedependent factors.Homer 1a increased
with sleepdeprivation independent of timing.Additionally, EEG
deltapower increased as expectedwith sleepdeprivation, but did
demonstratemodulationby timeof day. Thesefindings underline
the interactionbetweenobjectivemeasures originally thought to
reflect circadianor homeostatic control of sleep exclusively. (CG)
Invitro circadianperiod is associatedwith circadian/
sleeppreference.
Hida,A.,Kitamura, S.,Ohsawa,Y., Enomoto,M.,Katayose,Y.,
Motomura,Y., et al. (2013). SciRep, 3, 2074.
This study compared theperiod (tau) of invitro circadian rhythms
measuredwith clockgene expressionpatterns infibroblasts from
skinbiopsy samples,with taumeasuredunder a strict FDprotocol
and circadian/sleeps parametersmeasuredwithquestionnaires, sleep
diaries, and actigraphy in a real-world setting. Invitroperiod length
was correlated significantlywithhabitual sleep time, preferred
sleep time, and chronotype - but notwith invivoperiod length.
This study contributes toour understandingof the links between
behavioral and cellular rhythms, and furthers our understanding
ofmeasurement of peripheral clocks. Endogenous period length
(tau)may contribute to circadian rhythm sleep-wakedisorders.
Measurement of endogenous period length inhumans is labor
intensive; however, it requires that thepatients be studied in free-
runningor forceddesynchrony conditions. Amore convenient and
accessiblemethod formeasuringperiod length inhumans could
advanceour understandingof howperiod length contributes to
circadian rhythm sleep-wakedisorders. (KMS)
