Circadian Physiology Program

Division of Sleep and Circadian Disorders, Brigham and Women's Hospital
Director: Steven W. Lockley, Ph.D.


The Circadian Physiology Program focuses on basic and applied aspects of human circadian biology. Our translational approach includes use of a range of techniques including epidemiology, field-based physiological studies and inpatient intensive physiological monitoring.

We have a particular interest in human circadian photoreception and the effects of light on the circadian pacemaker and other non-image forming responses. Our studies include investigations of the effects of timing, duration, intensity and wavelength of light exposure on circadian resetting, melatonin suppression and the acute alerting effects of light. We are also conducting a series of applied lighting interventions to improve circadian rhythms, sleep and performance on the International Space Station and other NASA analogs, care homes, hospitals, and offices. This work is also being translated into architectural lighting design approaches and lighting standards.

We have studied visually impaired individuals under field and laboratory conditions to examine the effects of the severity and type of blindness on circadian photoreception, the periodicity of the circadian pacemaker and development of circadian rhythm sleep disorders, which led to the development of novel therapeutic strategies to treat non-24-hour sleep wake disorder in the blind, as well as other health risks such as breast cancer.

We have also conducted field and laboratory studies to assess the wider impact of circadian rhythms on a range of physiological systems including immune response, bone metabolism, reproductive function, liver function and lipid and glucose regulation, and are examining these systems in shiftwork and dementia. We are also identifying and validating a series of biomarkers to measure circadian phase and sleepiness under real-world conditions including lipidomics, metabolomics and urinomics and assessing other real-time circadian assessment technologies.

With the Harvard Work Hours Health and Safety Group, we assess the impact of extended work hours on health and safety of workers and the public. Our studies include the development of interventions that reduce extended duration work hours, fatigue and medical errors in hospital residents, and the implementation of large-scale occupational fatigue management and sleep disorders screening programs in police and firefighters nationwide.


Circadian Physiology Program
Division of Sleep and Circadian Disorders,
Departments of Medicine and Neurology
Brigham and Women’s Hospital
221 Longwood Avenue, RF-489
Boston, MA 02115
Tel: 617 732 4977
Fax: 617 732 4015

Group Members

Circadian Physiology Group
Circadian Physiology Program Group at the 2018 Sleep Health and Benefits Dinner: (L-R) Shadab A. Rahman, Leilah K. Grant, Brianne A. Kent, Melissa A. St. Hilaire, Steven W. Lockley

Circadian Physiology Program – 2019 sabbatical visit by Dr Vineetha Kalavally
Circadian Physiology Program – 2019 sabbatical visit by Dr. Vineetha Kalavally, Monash University Malaysia: (L-R) Matt Mayer, Shadab A. Rahman, Leilah K. Grant, Brianne A. Kent, Vineetha Kalavally, Steven W. Lockley

Steven W. Lockley, Ph.D.
Director, Circadian Physiology Program
Neuroscientist (part-time), Division of Sleep and Circadian Disorders, Brigham and Women’s Hospital
Associate Professor of Medicine (part-time), Harvard Medical School
Adjunct Professor and VC Fellow, Surrey Sleep Research Centre, University of Surrey, UK

Shadab A. Rahman, Ph.D., M.P.H.
Associate Neuroscientist, Division of Sleep and Circadian Disorders, Brigham and Women’s Hospital
Instructor in Medicine, Harvard Medical School

Melissa A. St. Hilaire, Ph.D.
Associate Biostatistician, Division of Sleep and Circadian Disorders, Brigham and Women’s Hospital
Instructor in Medicine, Harvard Medical School

Leilah K. Grant, Ph.D.
Associate Physiologist, Division of Sleep and Circadian Disorders, Brigham and Women’s Hospital
Instructor in Medicine, Harvard Medical School

Research Assistants

Matthew D. Mayer, B.S.

Phoebe Crosthwaite, B.S.

Affiliated Faculty

Shantha M. W. Rajaratnam, Ph.D.
Professor, Monash University, Australia
Sleep and Circadian Rhythms Program
School of Psychological Sciences
Deputy Head, School of Psychological Sciences
Deputy Director, Turner Institute for Brain and Mental Health
Lecturer in Medicine (Academic, part-time), Harvard Medical School

Former Fellows
  • Adriana Lira-Oliver, D.Des.
  • Joshua J. Gooley, Ph.D.
  • Eliza Van Reen, Ph.D.
  • Kate E. Crowley, Ph.D.
  • Brian K. Abaluck, M.D.
  • Melanie Rüger, Ph.D.
  • Joseph T. Hull, Ph.D.
  • Erin E. Flynn-Evans, Ph.D.
  • Brianne A. Kent, Ph.D.

Former PhD students
  • Joseph T. Hull (in collaboration with University of Surrey)
  • Erin E. Flynn-Evans (in collaboration with University of Surrey)
  • Julia Shekleton (in collaboration with Monash University)
  • Suzanne Ftouni (in collaboration with Monash University)
  • María L. Ámundadóttir (in collaboration with EPFL)
  • Simonne Cohen (in collaboration with Monash University)
  • Leilah K. Grant (in collaboration with Monash University)
  • Julia E. Stone (in collaboration with Monash University)
  • Saranea Ganesan (in collaboration with Monash University)
  • Laura J. Connolly (in collaboration with Monash University)
  • Lauren J. Bulfin (in collaboration with Monash University)
  • Lauren A. Booker (in collaboration with IBAS and Monash University)

Brigham and Women’s Hospital, Boston

  • Laura K. Barger, Ph.D.
  • Charles A. Czeisler, Ph.D., M.D.    
  • Hadine Joffe, M.D.
  • Elizabeth B. Klerman, M.D., Ph.D.    
  • Bruce S. Kristal, Ph.D.
  • Christopher P. Landrigan, M.D., M.P.H.    
  • Julian N. Robinson, M.D.
  • Jason P. Sullivan, B.S.
Current National and International Collaborators
  • George C. Brainard, Ph.D., Thomas Jefferson University, Philadelphia
  • Derk-Jan Dijk, Ph.D., Surrey Sleep Research Centre, University of Surrey, UK
  • Erin E. Flynn-Evans, Ph.D., NASA Ames, Moffett Field
  • Jennie Ponsford, Ph.D., Monash University, Melbourne, Australia
  • Christoph Reinhart, Ph.D., MIT, Cambridge
  • John Spengler, Ph.D., and Jose Guillermo (Memo) Cedeno Laurent, HSPH, Boston
  • Paula A. Witt-Enderby, Ph.D., Duquesne University, Pittsburgh
Selected Recent Publications from the Last 5 Years

[Full for list, click on Circadian Physiology Group Members' Papers]


Connolly LJ, Rajaratnam SMW, Murray JM, Spitz G, Lockley SW, Ponsford JL. Home-based light therapy for fatigue following acquired brain injury: A Pilot randomized controlled trial. BMC Neurology; 2021; in press.

Chen Y, Broman AT, Priest G, Landrigan CP, Rahman SA, Lockley SW. The effect of blue-enriched lighting on medical error rate in a university hospital ICU. Joint Commission Journal on Quality and Patient Safety, 2021; 47(3):165-175. PMID: 33341396

Barger LK, Sullivan JP, Lockley SW, Czeisler CA. Exposure to short wavelength-enriched white light and exercise improves alertness and performance in operational NASA flight controllers working overnight shifts. Journal of Occupational and Environmental Medicine 2021; 63(2):111-118. PMID: 33065729

Sletten TL, Raman B, Magee M, Ferguson SA, Kennaway DJ, Grunstein RR, Lockley SW, Rajaratnam SMW. A blue-enriched, increased intensity light intervention to improve alertness and performance in rotating night shift workers in an operational setting. Nature and Science of Sleep; 2021; May 24;13:647-657. PMID: 34079409 PMCID: PMC8163632

Rahman SA, Bibbo C, Olcese J, Czeisler CA, Robinson JN, Klerman EB. Relationship between endogenous melatonin concentrations and uterine contractions in late third trimester of human pregnancy. Journal of Pineal Research; 2019 May;66(4):e12566. PMID: 30739346

Sletten TL, Ftouni S, Nicholas CL, Magee M, Grunstein RR, Ferguson S, Kennaway DJ, O’Brien D, Lockley SW, Rajaratnam SMW. Randomised controlled trial of the efficacy of a blue-enriched light intervention to improve alertness and performance in night shift workers. Occupational and Environmental Medicine. 2017; 74(11):792-801. PMID: 28630378


Grant LK, Kent BA, Mayer MD, Stickgold R, Lockley SW, Rahman SA. Daytime exposure to short wavelength-enriched light improves cognitive performance in sleep-restricted college-aged adults. Frontiers in Neurology 2021; 12:624217. PMID: 33692742 PMCID: PMC7937889

Rahman SA, Brainard GC, Czeisler CA, Lockley SW. Spectral sensitivity of circadian phase resetting, melatonin suppression and acute alerting effects of intermittent light exposure. Biochemical Pharmacology 2021; in press. Mar 9:114504. PMID: 33711285

Rahman SA, Wright Jr KP, Lockley SW, Czeisler CA, Gronfier C. Characterizing the temporal dynamics of melatonin and cortisol changes in response to nocturnal light exposure. Scientific Reports 2019; 9(1):19720. PMID: 31873098 PMCID: PMC6928018

Phillips AJK*, Vidafar P*, Burns AC, McGlashan EM, Anderson C, Rajaratnam SMW, Lockley SW, Cain SW. High sensitivity and interindividual variability in the response of the human circadian system to evening light. Proceedings of the National Academy of Science USA 2019; 116(24):12019-12024. PMID: 31138694 PMCID: PMC6575863

Hanifin JP, Lockley SW, Cecil K, West K, Westa M, Jablonski M, Warfield B, James M, Ayers M, Byrne B, Gerner E, Pineda C, Rollag M, Brainard GC. Randomized trial of polychromatic blue-enriched light for circadian phase shifting, melatonin suppression, and alerting responses. Physiology and Behavior 2019; 198:57-66. PMID: 30296404

Rahman SA, St. Hilaire MA, Gronfier C, Chang AM, Santhi N, Czeisler CA, Klerman EB, Lockley SW. Functional decoupling of melatonin suppression and circadian phase resetting in humans. Journal of Physiology 2018; 596(11):2147-2157. PMID: 29707782

Rahman SA, St. Hilaire MA, Lockley SW. The effects of spectral tuning of evening ambient light on melatonin suppression, alertness and sleep. Physiology and Behavior 2017; 177: 221-229. PMID: 28472667

Rahman SA, St. Hilaire MA, Chang AM, Santhi N, Duffy JF, Kronaeur RE, Czeisler CA, Lockley SW, Klerman EB. Circadian phase resetting by a single short-duration light exposure. JCI Insight 2017; 2(7):e89494.PMID: 28405608 PMCID: PMC5374060


Vandewalle G*, van Ackeren MJ*, Daneault V, Hull JT, Albouy G, Lepore F, Doyon J, Czeisler CA, Dumont M, Carrier J, Lockley SW, Collignon O. Light modulates oscillatory alpha activity in the occipital cortex of totally visually blind individuals with intact non-image-forming photoreception. Scientific Reports 2018; 8(1):16968. PMID: 30446699 PMCID:PMC6240048

Hull JT, Czeisler CA, Lockley SW. Suppression of melatonin secretion in totally visually blind people by ocular exposure to white light: Clinical characteristics. Ophthalmology 2018; 125(8):1160-1171. PMID: 29625838

Flynn-Evans EE, Lockley SW. A pre-screening questionnaire to predict non-24 hour sleep wake rhythm disorder (N24HSWD) among the blind. Journal of Clinical Sleep Medicine 2016; 12(5):703-710. PMID: 26951421 PMCID:PMC4865557

Lockley SW, Dressman MA, Licamele L, Xiao C, Fisher DM, Flynn-Evans EE, Hull JT, Torres R, Lavedan C, Polymeropoulos MH. Two multicentre randomised trials of tasimelteon for treatment of Non-24-Hour Sleep-Wake Disorder in the blind. The Lancet 2015; 386(10005): 1754-1764. PMID: 26466871

St. Hilaire MA, Lockley SW. Caffeine does not entrain the circadian clock but improves daytime alertness in blind patients with non-24-hour rhythms [Brief Communication]. Sleep Medicine 2015; 16(6):800-4. PMID: 25891543 PMCID: PMC4465963


Grant LK, St. Hilaire MA, Brainard GC, Czeisler CA, Lockley SW, Rahman SA. Endogenous circadian regulation and phase resetting of clinical metabolic biomarkers. Journal of Pineal Research; 2021; in press. Jun 12:e12752. doi: 10.1111/jpi.12752. Online ahead of print. PMID: 34118084

Grant LK, Czeisler CA, Lockley SW, Rahman SA. Time-of-day and meal size effects on clinical lipid markers. Journal of Clinical Endocrinology and Metabolism 2021; 106(3):e1373-e1379. PMID: 33051649

Grant LK, Gooley JJ, St Hilaire MA, Rajaratnam SMW, Brainard GC, Czeisler CA, Lockley SW, Rahman SA. Menstrual phase-dependent differences in neurobehavioral performance: The role of temperature and the progesterone/estradiol ratio. Sleep 2020; 43(2). pii: zsz227. PMID: 31670824

Rahman SA, Grant LK, Gooley JJ, Rajaratnam SMW, Czeisler CA, Lockley SW. Endogenous circadian regulation of female reproductive hormones. Journal of Clinical Endocrinology and Metabolism 2019; 104(12):6049-6059. PMID: 31415086

Vidafar P, Gooley JJ, Burns AC, Rajaratnam SMW, Rueger M, Van Reen E, Czeisler CA, Lockley SW, Cain SW. Increased vulnerability to attentional failure during acute sleep deprivation in women depends on menstrual phase. Sleep 2018; 41(8). PMID: 29790961

St. Hilaire MA, Rahman SA, Gooley JJ, Witt-Enderby PA, Lockley SW. Relationship between melatonin and bone resorption rhythms in premenopausal women. Journal of Bone and Mineral Metabolism 2019; 37(1):60-71. PMID: 29318392

Grant LK, Ftouni S, Nijagal B, De Souza DP, Tull D, McConville MJ, Rajaratnam SW, Lockley SW, Anderson C. Circadian and wake-dependent changes in human plasma polar metabolites during prolonged wakefulness: A preliminary analysis. Scientific Reports 2019; 9(1):4428. PMID: 30872634 PMCID: PMC6418225

Bullock B, Murray G, Anderson JL, Cooper-O’Neil T, Gooley JJ, Cain SW, Lockley SW. Constraint is associated with earlier circadian phase and morningness: Confirmation of relationships between personality and circadian phase using a constant routine protocol. Personality and Individual Differences 2017; 104:69–74. PMID: 28216802

Rahman SA, Castanon-Cervantes O, Scheer FAJL, Shea SA, Czeisler CA, Davidson AJ, Lockley SW. Endogenous circadian regulation of pro-inflammatory cytokines and chemokines in the presence of bacterial lipopolysaccharide in humans. Brain, Behavior, and Immunity 2015; 47:4-13. PMID: 25452149.


Rahman SA, Rood D, Trent N, Solet J, Langer EJ*, Lockley SW*. Manipulating sleep duration perception changes cognitive performance – An exploratory analysis. Journal of Psychosomatic Research 2020; 132: 109992. PMID: 32172039

Sletten TL, Magee M, Murray JM, Gordon CJ, Lovato N, Kennaway DJ, Gwini SM, Bartlett DJ, Lockley SW, Lack LC, Grunstein RR, Rajaratnam SMW; for the Delayed Sleep on Melatonin (DelSoM) Study Group. Efficacy of melatonin with behavioural sleep-wake scheduling for delayed sleep-wake phase disorder: A double-blind, randomised clinical trial. PLoS Medicine 2018; 15(6):e1002587. PMID: 29912983 PMCID: PMC6005466

Flynn-Evans EE, Shekleton JA, Miller B, Epstein LJ, Kirsch D, Brogna LA, Burke LM, Bremer E, Murray JM, Gehrman P, Rajaratnam SMW, Lockley SW. Circadian phase and phase angle disorders in primary insomnia. Sleep 2017; 40(12). PMID: 29029340

Watson LA, Phillips AJK, Hosken IT,  McGlashan EM, Anderson C, Lack LC, Lockley SW, Rajaratnam SMW, Cain SW. Increased sensitivity of the circadian system to light in Delayed Sleep-Wake Phase Disorder. Journal of Physiology 2018; 596(24):6249-6261. PMID: 30281150

Cohen S*, Fulcher BD*, Rajaratnam SMW, Conduit R, Sullivan JP, St Hilaire MA, Philips AJK, Loddenkemper T, Kothare SV, McConnell K, Braga-Kenyon P, Ahearn W, Schlesinger A, Potter J, Bird F, Cornish KM, Lockley SW. Sleep patterns predictive of daytime challenging behavior in individuals with low-functioning autism. Autism Research 2018; 11(2):391-403. PMID: 29197172

Cohen S, Fulcher BD, Rajaratnam SMW, Conduit R, Sullivan JP, St Hilaire MA, Phillips AJ, Loddenkemper T, Kothare SV, McConnell K, Ahearn W, Braga-Kenyon P, Schlesinger A, Potter J, Bird F, Cornish KM, Lockley SW. Behaviorally-determined sleep phenotypes are robustly associated with adaptive functioning in individuals with low-functioning autism. Scientific Reports 2017; 7(1):142287. PMID: 29079761 PMCID: PMC5660229

Grima NA, Ponsford JL, St Hilaire MA, Mansfield D, Rajaratnam SM. Circadian melatonin rhythm following Traumatic Brain Injury. Neurorehabilitation and Neural Repair; 2016 Nov;30(10):972-977. PMID: 27221043


Brown LS, St Hilaire MA, McHill AW, Phillips AJK, Barger LK, Sano A, Czeisler CA, Doyle FJ 3rd, Klerman EB. A classification approach to estimating human circadian phase under circadian alignment from actigraphy and photometry data. Journal of Pineal Research; 2021 May 29:e12745. PMID: 34050968

Cochrane C, Ba D, Klerman EB, St Hilaire MA. An ensemble mixed effects model of sleep loss and performance. Journal of Theoretical Biology; 2021 Jan 21;509:110497. PMID: 32966825

Knock SA, Magee M, Stone JE, Ganesan S, Mulhall MD, Lockley SW, Howard ME, Rajaratnam SMW, Sletten TL, Postnova S. Prediction of shiftworker alertness, sleep, and circadian phase using a model of arousal dynamics constrained by shift schedules and light exposure. Sleep; 2021; in press. Jun 10:zsab146. PMID: 34111278

Murray JM, Magee M, Sletten TL, Gordon C, Lovato N, Ambani K, Bartlett DJ, Kennaway DJ, Lack LC, Grunstein RR, Lockley SW, Rajaratnam SMW, Phillips AJK; for the Delayed Sleep on Melatonin (DelSoM) Study Group. Light-based methods for predicting circadian phase in Delayed Sleep-Wake Phase Disorder. Scientific Reports 2021; 11(1):10878. PMID: 34035333

St Hilaire MA, Lammers-van der Holst HM, Chinoy ED, Isherwood CM, Duffy JF. Prediction of individual differences in circadian adaptation to night work among older adults: application of a mathematical model using individual sleep-wake and light exposure data. Chronobiology International; 2020 Sep-Oct;37(9-10):1404-1411. PMID: 32893681

Tekieh T, Lockley SW, Robinson PA, McCloskey S, Zobaer MS, Postnova S. Modelling melanopsin-mediated effects of light on circadian phase, melatonin suppression and subjective sleepiness. Journal of Pineal Research 2020; 69(3):e12681. PMID: 32640090

Kronauer RE, St Hilaire MA, Rahman SA, Czeisler CA, Klerman EB. An exploration of the temporal dynamics of circadian resetting responses to short- and long-duration light exposures: cross-species consistencies and differences. Journal of Biological Rhythms. 2019 Oct;34(5):497-514. PMID: 31368391

St. Hilaire MA, Kristal BS, Rahman SA, Sullivan JP, Quackenbush J, Duffy JF, Barger LK, Gooley JJ, Czeisler CA, Lockley SW. Using a single daytime performance test to identify most individuals at high-risk for performance impairment during extended wake. Scientific Reports 2019; 9(1):16681. PMID: 31723161 PMCID: PMC6853981

Chua EC, Sullivan JP, Duffy JF, Klerman EB, Lockley SW, Kristal BS, Czeisler CA, Gooley JJ. Classifying attentional vulnerability to total sleep deprivation using baseline features of Psychomotor Vigilance Test performance. Scientific Reports 2019; 9(1):12102. PMID: 31431644 PMCID: PMC6702200

Stone JE, Phillips AJK, Ftouni S, Magee M, Howard M, Lockley SW, Sletten TL, Anderson C, Rajaratnam SMW, Postnova S. Generalizability of a neural network model for circadian phase prediction in real-world conditions. Scientific Reports 2019; 9(1):11001. PMID: 31358781 PMCID: PMC6662750

Stone JE, Aubert XL, Maass H, Phillips AJK,Magee M, Howard ME, Lockley SW, Rajaratnam SMW, Sletten TL. Application of a limit-cycle oscillator model for prediction of circadian phase in rotating night shift workers. Scientific Reports 2019; 9(1):11032. PMID: 31363110 PMCID: PMC6667480

Postnova S, Lockley SW, Robinson PA. Prediction of cognitive performance and subjective sleepiness using a model of arousal dynamics. Journal of Biological Rhythms 2018; 33(2):203-218. PMID: 29671707

Abeysuriya RG, Lockley SW, Robinson PA, Postnova S. A unified model of melatonin, 6-sulfatoxymelatonin, and sleep dynamics. Journal of Pineal Research 2018; 64(4):e12474. PMID: 29437238

St. Hilaire MA*, Rüger M*, Fratelli F, Hull JT, Phillips AJK, Lockley SW. Modeling neurocognitive decline and recovery during repeated cycles of extended sleep and chronic sleep deficiency. Sleep 2017; 40(1). doi: 10.1093/sleep/zsw009. PMID: 28364449


Rahman SA, Sullivan JP, Barger LK, St. Hilaire MA, O’Brien CS, Stone KL, Phillips AJK, Klerman EB, Qadri S, Wright Jr KP, Halbower AC, Segar JL, McGuire JK, Vitiello MV, de la Iglesia HO, Poynter SE, Yu PL, Sanderson AL, Zee PC, Landrigan CP, Czeisler CA, Lockley SW for the ROSTERS Study Group. Extended work shifts and neurobehavioral performance in resident-physicians. Pediatrics 2021; 147(3):e2020009936. PMID: 33619044

Landrigan CP, Rahman SA, Sullivan JP, Vittinghoff E, Barger LK, Sanderson AL, Wright Jr KP, O’Brien CS, Qadri S, St. Hilaire MA, Halbower AC, Segar JL, McGuire JK, Vitiello MV, de la Iglesia HO, Poynter SE, Yu PL, Zee PC, Lockley SW, Stone KL, Czeisler CA, for the ROSTERS Study Group. Effect on patient safety of a resident physician schedule without 24 hour Shifts. New England Journal of Medicine 2020; 382(26): 2514-2523. PMID: 32579812

Booker LA, Barnes M,  Alvaro P, Collins A, Chai-Coetze CL, McMahon M, Lockley SW, Rajaratnam SMW, Howard ME. Sletten TL. The role of sleep hygiene in the risk of Shift Work Disorder in nurses. Sleep 2020; 43(2). pii: zsz228. PMID: 31637435

Booker LA, Sletten TL, Alvaro PK, Barnes M, Collins A, Chai-Coetze CL, Naqvi A, McMahon M, Lockley SW, Rajaratnam SMW, Howard ME. Exploring the associations between shift work disorder, depression, anxiety and sick leave taken amongst nurses. Journal of Sleep Research 2020; 29(3):e12872. PMID:  31144389

Razavi P, Devore EE, Bajaj A, Lockley SW, Figueiro MG, Ricchiuti V, Gauderman WJ, Hankinson SE, Willett WC, Schernhammer E. Shift work, chronotype, and melatonin rhythm in nurses. Cancer Epidemiology, Biomarkers & Prevention 2019; 28(7):1177-1186. PMID: 31142495

Barger LK, Sullivan JP, Blackwell T, O’Brien CS, St. Hilaire MA, Rahman SA, Phillips AJK, Qadri S, Wright KP, Segar JL, McGuire JK, Vitiello MV, de la Iglesia HO, Poynter SE, Yu PL, Zee PC, Sanderson AL, Halbower AC, Lockley SW, Landrigan CP, Stone KL, Czeisler CA;ROSTERS Study Group. Effects on resident work hours, sleep duration and work experience in a Randomized Order Safety Trial Evaluating Resident-physician Schedules (ROSTERS). Sleep 2019; 42(8). PMID: 31106381

Mulhall MD, Sletten TL, Magee M, Stone JE, Ganesan S, Collins A, Anderson C, Lockley SW, Howard ME, Rajaratnam SMW. Sleepiness and driving events in shift workers: The impact of circadian and homeostatic factors. Sleep 2019; 42(6). PMID: 30882154

Ganesan S, Magee M, Stone JE, Mulhall MD, Collins A, Howard ME, Lockley SW, Rajaratnam SMW, Sletten TL. The impact of shiftwork on sleep, alertness and performance in healthcare workers. Scientific Reports 2019; 9(1):4635. PMID: 30874565 PMCID:   PMC6420632

St. Hilaire MA, Anderson C, Anwar J, Sullivan JP, Cade BE, Flynn-Evans EE, Czeisler CA, Lockley SW; for the Harvard Work Hours Health and Safety Group. Brief (<4 hour) sleep episodes are insufficient for restoring performance in first-year resident physicians working overnight extended-duration work shifts. Sleep 2019; 42(5). PMID: 30794317

Stone JE, Sletten TL, Magee M, Ganesan S, Mulhall MD, Collins A, Howard M, Lockley SW, Rajaratnam SMW. Temporal dynamics of circadian phase shifting response to consecutive night shifts in healthcare workers: Role of light-dark exposure. Journal of Physiology 2018; 596(12):2381-2395. PMID: 29589871

Anderson C, Ftouni S, Ronda JM, Rajaratnam SMW, Czeisler CA, Lockley SW. Self-reported drowsiness and safety outcomes while driving after an extended duration work shift in trainee physicians. Sleep 2018; 41(2) zsx195. PMID: 29281091


Peterson SA*, Wolkow AP*, Lockley SW, O’Brien CS, Qadri S, Sullivan JP, Czeisler CA, Rajaratnam SMW, Barger LK. Associations between shift work characteristics, shift work schedules, sleep and burnout in North American police officers: a cross-sectional study. BMJ Open 2019; 9(11):e030302. PMID: 31791964 PMCID: PMC6924705

Wolkow AP, Barger LK, O’Brien CS, Sullivan JP, Qadri S, Lockley SW, Czeisler CA, Rajaratnam SMW. Associations between sleep disturbances, mental health outcomes and burnout in firefighters, and the mediating role of sleep during overnight work: A cross-sectional study. Journal of Sleep Research 2019; e12869. PMID: 31131535

Ogeil RP, Barger LK, Lockley SW, O'Brien CS, Sullivan JP, Qadri S, Lubman DI, Czeisler CA, Rajaratnam SMW. Cross-sectional analysis of sleep-promoting and wake-promoting drug use on health, fatigue-related error and near crashes in police officers. BMJ Open 2018; 8(9):e022041. PMID: 30232109 PMCID:PMC6150149

Sullivan JP, O’Brien CS, Barger LK, Rajaratnam SMW, Czeisler CA, Lockley SW; The Harvard Work Hours, Health and Safety Group. Randomized, prospective study of the impact of a workplace-based sleep health program on firefighter injury and disability. Sleep 2017; 40(1). doi: 10.1093/sleep/zsw001. PMID: 28364446


Kelley P, Lockley SW, Kelley J, Evans MDR. Is 8:30 a.m. still too early to start school? A 10:00 a.m. school start time improves health and performance of students aged 13-16. Frontiers in Human Neuroscience 2017; 11:588. PMID: 29276481 PMCID: PMC5727052

Phillips AJK*, Clerx WM*, O’Brien CS, Sano A, Barger LK, Picard RW, Lockley SW, Klerman EB, Czeisler CA. Irregular sleep/wake patterns are associated with poorer academic performance and delayed circadian and sleep/wake timing. Scientific Reports 2017; 7(1):3216. PMID: 28607474 PMCID: PMC5468315

Selected Recent Research Support

Vanda Pharmaceuticals (Site PI: Lockley)     2021-2022

Sponsor-initiated trial “A multicenter, double-blind, randomized study to evaluate the effects of tasimelteon vs. placebo in participants with Delayed Sleep-Wake Phase Disorder (DSWPD)”

This is a multicenter, double-blind, randomized study to evaluate the efficacy and safety of a daily single oral dose of tasimelteon and matching placebo in male and female participants with DSWPD.

BIOS, LLC (PI: Rahman)                               06/11/20 - 06/10/25

Investigator-initiated study “The effect of lighting supplementation on cognitive task performance during the day”

The goal of this project is to examine whether supplementing existing poor quality indoor lighting with blue-enriched white lighting can improve daytime cognitive performance in healthy young adults.

Seoul Semiconductor (PI: Rahman)               01/11/19-01/10/24

Investigator-initiated study “Effects of daytime lighting conditions on students' cognitive performance”

The goal is to assess the role light spectrum and intensity on the alerting effects of daytime light exposure.

FAA    (Co-PIs: Klerman, Czeisler)                09/18/19-09/17/21

FAA “Comparison across multiple types of sleep deprivation”.

This contracted work will collect data for the FAA for discovery of biomarkers associated with neurobehavioral or cognitive impairment during sleep loss and mistimed sleep. Role: Co-Investigator

PNNL (PI: Rahman)                                       09/10/19-08/31/21

Investigator-initiated study “analyzing de-identified patient data for an inpatient behavioral health unit research”

The goals are to assess the role of light on health outcomes in an inpatient facility. Role: Co-Investigator

1R21NR018974 (PI: St Hilaire)                     09/25/19-07/31/21

NINR ‘Urine metabolomics to estimate internal clock time’

The goals are to develop a feasible method to measure circadian phase accurately and reliably using non-invasive urinomics. Role: Co-Investigator

NNX15AC14G (Co-PIs: Brainard, Lockley) 12/01/14-09/30/21

NASA “Testing solid state lighting countermeasures to improve circadian adaptation, sleep, and performance during high fidelity analog and flight studies for the International Space Station”.

Recently completed

F.lux Software, LLC   (PI: Lockley)               08/28/15-08/27/20                  

Investigator-initiated study “Measuring the effects of light from electronic devices on sleep”

We propose to conduct a randomized clinical trial on the effects of reducing blue content of light emitted from electronic devices on sleep using the F.Lux software.

NNX15AM28G          (PI: Lockley)               08/13/15-06/30/20

NASA “Lighting Protocols for Exploration – HERA Campaign”

The study will examine the feasibility and efficacy of a Dynamic Lighting System to improve alertness, sleep and circadian rhythms in the Human Exploration Research Analog.

NNX14AK53G (PI: Lockley)                         08/01/14-01/31/20 (NCE)      

NSBRI “Development and testing of biomarkers to determine individual astronauts’ vulnerabilities to behavioral health disruptions”

This study will evaluate biomarkers that will test the sensitivity of various sleep and circadian challenges to differentiate individuals.

Midwest Lighting Institute (PI: Rahman)       01/01/18-12/31/19

“Senior care facility lighting to improve health, safety and energy efficiency”.

The goal of this project is to examine the impact of a dynamic lighting intervention on the health and safety of seniors living in care homes. Role: Co-Investigator.

1R01HL132556 (PI: Kristal)                          04/18/16-03/31/20                  

NHLBI “Circadian Lipidomics in Constant Routine, Forced Desynchrony, and Non-lab Setting”

The goals of this project are to identify, optimize, validate, and to cross-validate a set of nested plasma lipidomics-based biomarker profiles that report circadian phase.

In the News