Trainee Profile

Sarah L. Chellappa, MD, PhD

Sarah Chellappa profile photo
Research Fellow, Harvard Medical School
Post-doctoral Research Fellow, Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital

See publications


221 Longwood Avenue
036 BLI, Room 039C
Boston, MA 02115

Inter-office Mail Address

036 BLI, Room 039C

Phone 617-525-9086


Society Memberships

European Sleep Research Society
European Biological Rhythms Society
Society for Sleep Research

Section Editor (Light research) for “Clock and Sleep” (Journal / MPDI)

Research Unit(s)

Division of Sleep Medicine
Medical Chronobiology Group 

Research Interests

Contemporary 24-h/7-day lifestyle comes with a heavy price to pay: more than 8 million Americans work at night, and at least 32% meet the minimal diagnostic criteria for shift work disorder (SWD), defined by the International Classification of Sleep Disorders (ICSD-2) as a major circadian rhythm sleep disorder. Importantly, the clinical risks/consequences of shift work and SWD comprise, but are not limited to, metabolic disorders, including type 2 diabetes (T2D) and cardiovascular diseases. Despite recent breakthroughs on this clinical phenomenon, knowledge on normal and pathological responses to the circadian stress of artificial sleep schedules associated with shift work remains uncertain. Previous work at the Medical Chronobiology Program has demonstrated that misalignment between the circadian pacemaker and behavioral cycles (sleep/wake and fasting/feeding)—typical in shift workers—leads to adverse metabolic changes. Based on these findings, the goal of my research is to investigate whether manipulation of food timing can prevent adverse metabolic effects in humans, and what are the basic underlying mechanisms. The insights provided by this research approach may lead to a novel treatment paradigm of metabolic risk, particularly in vulnerable populations, e.g. shift work and SWD.


Selected Publications

Gaggioni G*, Ly JQM*, Chellappa SL*, Coppieters 't Wallant D, Rosanova M, Sarasso S, Luxen A, Salmon E, Middleton B, Massimini M, Schmidt C, Casali A, Phillips C,  Vandewalle G. Human fronto-parietal response scattering subserves vigilance at night. Neuroimage. 2018;175:354-364. doi:10.1016/j.neuroimage.2018.03.055. [Epub ahead of print] 
PMID: 29604455.
* Shared first authorship

Chellappa SL*, Morris CJ*, Scheer FAJL. Daily circadian misalignment impairs
human cognitive performance task-dependently. Sci Rep. 2018;8(1):3041. doi: 10.1038/s41598-018-20707-4. PMID: 29445188;  PMCID:PMC5812992.
* Shared first authorship

Chellappa SL, Lasauskaite R, Cajochen C. In a Heartbeat: Light and Cardiovascular Physiology. Front Neurol. 2017;8:541. doi: 10.3389/fneur.2017.00541. eCollection 2017. Review. PMID: 29104560; PMCID: PMC5654948.

Chellappa SL, Steiner R, Oelhafen P, Cajochen C. Sex differences in light
sensitivity impact on brightness perception, vigilant attention and sleep in humans. Sci Rep. 2017 Oct 27;7(1):14215. doi: 10.1038/s41598-017-13973-1.
PMID: 29079823; PMCID: PMC5660221.

Birchler-Pedross A, Frey S, Götz T, Brunner P, Knoblauch V, Wirz-Justice A,
Chellappa SL*, Cajochen C*. Subjective Mood in Young Unmedicated Depressed Women
under High and Low Sleep Pressure Conditions. Biology (Basel). 2016 Dec 9;5(4).
pii: E52. PMID: 27941666; PMCID: PMC5192432.
* Shared senior authorship

Cajochen C, Chellappa SL. Commentary: Melanopsin Regulates Both
Sleep-Promoting and Arousal-Promoting Responses to Light. Front Neural Circuits.
2016 Nov 16;10:94. eCollection 2016. PMID: 27899883; l PMCID:PMC5110526.

Chellappa SL, Gaggioni G, Ly JQ, Papachilleos S, Borsu C, Brzozowski A,
Rosanova M, Sarasso S, Luxen A, Middleton B, Archer SN, Dijk DJ, Massimini M, Maquet P, Phillips C, Moran RJ, Vandewalle G. Circadian dynamics in measures of cortical excitation and inhibition balance. Sci Rep. 2016 Sep 21;6:33661. doi: 10.1038/srep33661.
PMID: 27651114;  PMCID: PMC5030482.

Muto V, Jaspar M, Meyer C, Kussé C, Chellappa SL, Degueldre C, Balteau E,
Shaffii-Le Bourdiec A, Luxen A, Middleton B, Archer SN, Phillips C, Collette F,
Vandewalle G, Dijk DJ, Maquet P. Local modulation of human brain responses by
circadian rhythmicity and sleep debt. Science. 2016 Aug 12;353(6300):687-90. doi:
10.1126/science.aad2993. Erratum in: Science. 2016 Dec 23;354(6319):.
PMID: 27516598.

Ly JQ*, Gaggioni G*, Chellappa SL*, Papachilleos S, Brzozowski A, Borsu C,
Rosanova M, Sarasso S, Middleton B, Luxen A, Archer SN, Phillips C, Dijk DJ,
Maquet P, Massimini M, Vandewalle G. Circadian regulation of human cortical
excitability. Nat Commun. 2016 Jun 24;7:11828. doi: 10.1038/ncomms11828.
PMID: 27339884; PMCID: PMC4931032.
* Shared first authorhip

Vanvinckenroye A, Vandewalle G, Phillips C, Chellappa SL. Eyes Open on Sleep
and Wake: In Vivo to In Silico Neural Networks. Neural Plast. 2016:1478684.
doi: 10.1155/2016/1478684. Epub 2016 Jan 14. [PMID: 26885400]

Meyer C, Muto V, Jaspar M, Kussé C, Lambot E, Chellappa SL, Degueldre C,
Balteau E, Luxen A, Middleton B, Archer SN, Collette F, Dijk DJ, Phillips C,
Maquet P, Vandewalle G. Seasonality in human cognitive brain responses. Proc Natl
Acad Sci U S A. 2016 Feb 8. pii: 201518129. [PMID:26858432]

't Wallant DC, Muto V, Gaggioni G, Jaspar M, Chellappa SL, Meyer C, Vandewalle
G, Maquet P, Phillips C. Automatic artifacts and arousals detection in
whole-night sleep EEG recordings. J Neurosci Methods. 2016 Jan 30;258:124-33.
[PMID: 26589687]

Viola AU, Gabel V, Chellappa SL, Schmidt C, Hommes V, Tobaldini E, Montano N,
Cajochen C. Dawn simulation light: a potential cardiac events protector. Sleep
Med. 2015 Apr;16(4):457-61. [PMID: 25813092]

Gabel V, Maire M, Reichert CF, Chellappa SL, Schmidt C, Hommes V, Cajochen C,
Viola AU. Dawn simulation light impacts on different cognitive domains under
sleep restriction. Behav Brain Res. 2015 Mar 15;281:258-66. [PMID: 25549858]

Ziegler E, Chellappa SL, Gaggioni G, Ly JQ, Vandewalle G, André E, Geuzaine C,
Phillips C. A finite-element reciprocity solution for EEG forward modeling with
realistic individual head models. Neuroimage. 2014 Dec;103:542-51. [PMID: 25204867]

Chellappa SL, Viola AU, Schmidt C, Bachmann V, Gabel V, Maire M, Reichert CF,
Valomon A, Landolt HP, Cajochen C. Light modulation of human sleep depends on a
polymorphism in the clock gene Period3. Behav Brain Res. 2014 Sep 1;271:23-9.
[PMID: 24893318]

Chellappa SL, Ly JQ, Meyer C, Balteau E, Degueldre C, Luxen A, Phillips C,
Cooper HM, Vandewalle G. Photic memory for executive brain responses. Proc Natl
Acad Sci U S A. 2014 Apr 22;111(16):6087-91. [PMID: 24616488]

Gabel V, Maire M, Reichert CF, Chellappa SL, Schmidt C, Hommes V, Viola AU,
Cajochen C. Effects of artificial dawn and morning blue light on daytime
cognitive performance, well-being, cortisol and melatonin levels. Chronobiol Int.
2013 Oct;30(8):988-97. [PMID: 23841684]

Chellappa SL, Steiner R, Oelhafen P, Lang D, Götz T, Krebs J, Cajochen C.
Acute exposure to evening blue-enriched light impacts on human sleep. J Sleep
Res. 2013 Oct;22(5):573-80. [PMID: 23509952]

Chellappa SL, Viola AU, Schmidt C, Bachmann V, Gabel V, Maire M, Reichert CF,
Valomon A, Götz T, Landolt HP, Cajochen C. Human melatonin and alerting response
to blue-enriched light depend on a polymorphism in the clock gene PER3. J Clin
Endocrinol Metab. 2012 Mar;97(3):E433-7. [PMID: 22188742]

Viola AU, Chellappa SL, Archer SN, Pugin F, Götz T, Dijk DJ, Cajochen C.
Interindividual differences in circadian rhythmicity and sleep homeostasis in
older people: effect of a PER3 polymorphism. Neurobiol Aging. 2012
May;33(5):1010.e17-27. [PMID: 22169200]

Birchler-Pedross A, Frey S, Chellappa SL, Götz T, Brunner P, Knoblauch V,
Wirz-Justice A, Cajochen C. Higher frontal EEG synchronization in young women
with major depression: a marker for increased homeostatic sleep pressure? Sleep.
2011 Dec 1;34(12):1699-706. [PMID: 22131608]

Chellappa SL, Münch M, Knoblauch V, Cajochen C. Age effects on spectral
electroencephalogram activity prior to dream recall. J Sleep Res. 2012
Jun;21(3):247-56. [PMID: 21851439]

Viola AU, Tobaldini E, Chellappa SL, Casali KR, Porta A, Montano N.
Short-term complexity of cardiac autonomic control during sleep: REM as a
potential risk factor for cardiovascular system in aging. PLoS One. 2011 Apr
22;6(4):e19002. [PMID: 21544202]

Chellappa SL, Frey S, Knoblauch V, Cajochen C. Cortical activation patterns
herald successful dream recall after NREM and REM sleep. Biol Psychol. 2011
May;87(2):251-6. [PMID: 21419827]

Chellappa SL, Steiner R, Blattner P, Oelhafen P, Götz T, Cajochen C.
Non-visual effects of light on melatonin, alertness and cognitive performance:
can blue-enriched light keep us alert? PLoS One. 2011 Jan 26;6(1):e16429. [PMID: 21298068]

Chellappa SL, Münch M, Blatter K, Knoblauch V, Cajochen C. Does the circadian
modulation of dream recall modify with age? Sleep. 2009 Sep;32(9):1201-9. [PMID: 19750925]

Chellappa SL, Araújo JF. Sleep disorders and suicidal ideation in patients
with depressive disorder. Psychiatry Res. 2007 Oct 31;153(2):131-6. Epub 2007 Jul
20. [PMID: 17658614]

Chellappa SL, Araújo JF. Excessive daytime sleepiness in patients with
depressive disorder. Rev Bras Psiquiatr. 2006 Jun;28(2):126-9. Epub 2006 Jun 26.
[PMID: 16810396]


Chellappa SL, Cajochen C. Ultradian and circadian modulation of dream recall:
EEG correlates and age effects. Int J Psychophysiol. 2013 Aug;89(2):165-70. [PMID: 23524011]

Chellappa SL, Gordijn MC, Cajochen C. Can light make us bright? Effects of
light on cognition and sleep. Prog Brain Res. 2011;190:119-33. [PMID: 21531248]

Cajochen C, Chellappa S, Schmidt C. What keeps us awake? The role of clocks
and hourglasses, light, and melatonin. Int Rev Neurobiol. 2010;93:57-90. [PMID: 20970001]

Chellappa SL, Schröder C, Cajochen C. Chronobiology, excessive daytime
sleepiness and depression: Is there a link? Sleep Med. 2009 May;10(5):505-14.
doi: 10.1016/j.sleep.2008.05.010. Epub 2008 Sep 27. [PMID:18824409]

Book chapters

Ly JQM*, Chellapa SL*, Maquet P. Evolution of Treatment and Investigative Approaches in Sleep Medicine. In: Michael Billiard (Org), Sleep Medicine: a comprehensive guide. Elsevier
prublications. 2016.(* Shared first authorship) (In press).

Chellappa SL, Schmidt C, Cajochen C. Neurophysiological basis of sleep and wakefulness.In: Sergio Garbarino (Org), Sleepiness and Human Impact Assessment. Springer Science. 2014, p.23-42.

Cajochen C, Schmidt C, Chellappa SL. Circadian and light effects on human sleepiness-alertness. In: Sergio Garbarino (Org), Sleepiness and Human Impact Assessment. Springer Science. 2014. p.9-22.

Schmidt C, Chellappa SL, Cajochen C. Circadian and homeostatic regulation of sleepiness, cognition, and their neuronal underpinnings. In: Sergio Garbarino (Org), Sleepiness and Human Impact Assessment. Springer Science. 2014. p.43-62.

Chellappa SL, Viola AU, Mongrain V. Circadian Rhythm Sleep Disorder: Genetic and Environmental Factors. In: Clete Kushida (Org.), Encyclopaedia of Sleep. Elsevier publications. 2013. p.4-10.

Chellappa SL, Cajochen C. Depression and sleepiness: A chronobiological approach. In: Michael Thorpy; Michael Billiard (Org.), Sleepiness Causes, Consequences and Treatment. New York: Cambridge University Press, 2011.

Chellappa SL, Chellappa SL, Cajochen C. The Circadian Clock and the homeostatic
hourglass - two timepieces controlling Sleep and wakefulness. In: The circadian clock, edited by Kluwer Academic / Plenun Publishing Corporation (Springer Science), 2010.

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