Charles Czeisler Explained

Charles Czeisler
Academic Advisors:William C. Dement
Elliot D. Weitzman
Known For:Human sleep medicine
Circadian rhythm research
Awards:Aschoff's Rule
National Sleep Foundation: Lifetime Achievement Award
Royal College of London: Adrian Gold Medal
Stanford Medicine Alumni Association: J.E. Wallace Sterling Lifetime Achievement Award in Medicine
Harvard Medical School Division of Sleep Medicine: Peter C. Farrell Prize in Sleep Medicine
Website:Harvard Neuroscience faculty page
Harvard Medical School faculty profile

Charles Andrew Czeisler (born November 1952) is a Hungarian-American physician and sleep and circadian researcher.[1] He is a leading researcher and author in the fields of the effects of light on human physiology, circadian rhythms and sleep medicine.

Background and education

Czeisler graduated from Harvard College, magna cum laude in 1974, with a degree in biochemistry and molecular biology. His undergraduate thesis was focused on cortisol timing release.[2] He then studied at Stanford University, where he received his Ph.D. in neuro- and bio-behavioral sciences in 1978 and his M.D. in 1981.[3] As a graduate student at Stanford, Czeisler continued his research in Dr. William Dement's lab. Dr. Elliot Weitzman, who both worked with and mentored Czeisler, influenced Czeisler to study sleep. Today, Czeisler is the Baldino Professor of Sleep Medicine and Director of the Division of Sleep Medicine at Harvard Medical School. Additionally, he works as the Division Chief of Sleep Medicine at Brigham and Women's Hospital in Boston, Massachusetts.[4]

Czeisler has spent over 40 years researching the relationship between light and human physiology, particularly, the physiology of the human circadian clock. He teaches a course at Harvard College on Circadian Biology for undergraduate and graduate students.[5] He was ultimately inducted into the Phi Beta Kappa Society (ΦΒΚ) at Harvard College in 1999. In addition to his work at Harvard Medical School and Brigham and Women's Hospital, Czeisler is a Diplomate of the American Board of Sleep Medicine, an elected member of the National Academy of Medicine, the International Academy of Astronautics and the American Clinical and Climatological Association, and a Fellow of the Royal College of Physicians, American Society for Clinical Investigation, and Association of American Physicians.

Family life

Czeisler was one of Tibor Czeisler and Wanda Victoria Murzyn's three children. In 1993, Czeisler married Theresa Lynn Shanahan M.D. They now have three children and live in the Boston area. In his free time, Czeisler enjoys swimming, playing pickleball, and slalom waterskiing.

Research interests

Czeisler's research focus is the neurobiology of human circadian rhythm, the functions and physiology of sleep, the epidemiology and public health consequences of sleep disorders, and the applications of circadian and sleep principles in clinical medicine and occupational safety and health. He also examines the relationship between the circadian oscillator and sleep homeostasis, including a landmark 1980 Science paper demonstrating that sleep episodes were correlated with the circadian phase of the body temperature rhythm at bedtime and not with the length of prior wakefulness.[6] Czeisler's research interests encompass many areas, including the effects of light on human circadian rhythms, the role of sleep and circadian rhythms in metabolism, the impact of shift work on health and productivity, and the effects of melatonin and melatonin receptor agonists on humans.

Czeisler investigates how the physiological system works to reset the human central circadian pacemaker, located in the hypothalamus and called the suprachiasmatic nucleus (SCN).[7] Among his most salient contributions to this research area are a pair of seminal Science original research articles published in 1986[8] and 1989.[9] The first, entitled "Bright light resets the human circadian pacemaker independent of the timing of the sleep-wake cycle," provided convincing evidence that light influences the human circadian pacemaker, contributing to control of daily variations in physiologic, behavioral, and cognitive function. This finding challenged the then-common idea that synchronization to the 24-hour day accomplished either through social contacts or the sleep-wake schedule. This scientific breakthrough was featured on the front page of The New York Times in June 1989.

Czeisler then led the discovery that light transduced by non-visual input (melanopsin activation) could reset the circadian clock in patients without sight.[10] [11] This indicated that some blind humans can entrain to light through non-visual photoreceptors. Czeisler found that intrinsically photosensitive retinal ganglion cells (ipRGCs) influence both the circadian clock and visual perception, indicating that ipRGCs contribute to "visual" light perception even in the absence of rod and cone photoreceptors.[12] Significantly, this challenged the misconception that rod and cone photoreceptors were the sole receptors for photo-entrainment in humans.[13] [14] In 2002, Czeisler published a study that defended the long-held notion that mammals do not have extra-occular photoreceptors.[15] The findings of his study definitively refuted those of the famous 1998 Science publication, "Extraocular Circadian Phototransduction in Humans," which had reported that bright light behind the knees can help regulated human circadian photoentrainment. Czeisler's study debunked the 1998 publication.

Czeisler has examined the effects of sleep deprivation on the sleep-wake cycle and circadian rhythms, and how this impacts attention performance.[16] He found that bright light duration impacts the circadian pacemaker, melatonin suppression, and sleepiness.[17] He has also discovered that even room lighting can suppress melatonin production and its duration.[18] Czeisler has also dedicated a portion of his career to examining the effects of light timing, duration, intensity, and wavelength on resetting the pacemaker through ipRGCs, which contain the photopigment melanopsin.

Czeisler's work has many important applications. He showed that sleep deprivation could have adverse consequences affecting obesity and diabetes, among other health problems.[19] He has also investigated the effects of chronic sleep deprivation and restriction, night shifts, and circadian disruption, on neurobehavioral performance and metabolism.[20] Furthermore, Czeisler studied how sleep deprivation impairs the psychomotor performance of night shift workers (2009-2014), specifically surgeons (2009-2013) and residents (2010), police officers (2004-2008),[21] and truck drivers (2012). Other research interests of his include studying wakefulness, sleep deprivation and how it can be prevented, and such influences on the clock as exercise and age. Czeisler's research has been applied to medicine, space travel, and night occupations including shift-work.

As of August 2023, Czeisler has published more than 300 scientific articles, which have accumulated more than 80,000 citations, leading to an h-index of 138.[22]

Summary of selected contributions

Advocacy in sleep health and occupational safety

In a 1999 interview with the Harvard Gazette regarding his team's characterization of a near-24-hour human circadian period, Czeisler noted that "accepting the near-24-hour period means that all the ideas about daily human rhythms that we take for granted must be rethought."[39] Understanding the internal circadian period makes problems dealing with jet-lag, night shifts, and sleep schedules in orbit more approachable

Guided by the significant real-life implications of his research, Czeisler is a strong advocate for healthy sleep habits. In consulting with the Boston Celtics, Portland Trail Blazers, and Minnesota Timberwolves for the National Basketball Association (NBA) and Cleveland Browns for the National Football League (NFL), he emphasized sleep as the "third pillar of health" alongside nutrition and exercise.[40] He instituted structural changes to the teams' schedules to allow for healthier sleep habits, including pushing morning practices into the afternoon and the '2 a.m. rule' which prevents players from traveling if they are going to arrive at their hotel later than 2:00 am.[41]

According to Czeisler, sleep deficiency poses a significant individual and public health hazard as demonstrated by the significant contribution of drowsiness to workplace accidents and motor vehicle accidents. In an interview with the Harvard Business Review, he explains that companies should seek to address this problem by setting behavioral expectations and scheduling policies for employees to avoid accruing sleep deficit.[42]

In order to implement improved occupational sleep scheduling and sleep health standards as effective public policy, Czeisler has served on and consulted to numerous national and international health advisory agencies. As President of the National Sleep Foundation from 2005–2006, he chaired the Presidential Task Force on Sleep and Public Policy in order to develop model legislation regarding physician-in-training work hours.[43] [44] As a Team Leader of the Human Performance Factors, Sleep and Chronobiology Team at the NASA National Space Biomedical Research Institute, Czeisler has been responsible for developing sleep-wake schedule guidelines for NASA astronauts and mission control personnel.

Czeisler is also a member of the Brigham Health Sleep Matters Initiative,(SMI) which was created "to implement evidence-based clinical treatments for sleep and circadian disorders, and to change the culture of sleep." In 2018, the National Safety Council recognized the SMI for its outstanding commitment to safety, for which it was awarded the prestigious Green Cross for Safety Award.[45]

In 2018, Czeisler penned a powerful Perspective in The New England Journal of Medicine entitled "Housing Immigrant Children - The Inhumanity of Constant Illumination"[46] in which he harshly criticized the constant light exposure to which children were being subjected in detention centers while awaiting immigration processing, as this did not allow for exposure to light-dark cycles central to circadian regulation.

In 2023, together with Harvard Medical School Professor Elizabeth Klerman, Czeisler organized a seminar at the Harvard Radcliffe Institute to discuss whether daylight saving time should be eliminated or made permanent—a debate they call “another clash between scientific evidence and politics.” The seminar brought together researchers, policymakers, and members of the general public for a discussion.

A more complete listing of agencies to which Czeisler has consulted[46] can be found at his Harvard Faculty Profile.[47]

Honors and awards

Czeisler's research in sleep medicine, circadian rhythms, and professional advocacy for occupational health and safety, are the subject of various honors and awards included below:

Czeisler is a co-inventor of several U.S. patents:

During October 2019, a Festschrift was organized to celebrate Czeisler's career. The event was held in the Harvard Biological Laboratories, where Czeiser's colleagues, former pupils, friends, and family gathered to present plenary speeches and breakthrough scientific talks. The occasion brought together approximately 75 researchers from six different continents.

A more complete list of honors and awards bestowed upon Czeisler can be found on his Harvard Faculty Profile

Notes and References

  1. Czeisler, Charles A. E-mail interview. 24 April 2013.
  2. "Charles Czeisler." Interview. The Science Network. N.p., June 2009. Web. 23 Apr. 2013.
  3. "Faculty Profile: Charles A. Czeisler, PhD, MD, FRCP." Division of Sleep Medicine: Harvard Medical School. Harvard College, n.d. Web. 10 Apr. 2013.https://sleep.med.harvard.edu/people/faculty/210/
  4. "Division of Sleep Medicine." Brigham and Women's Hospital. The Division of Sleep Medicine, 25 Jan. 2013. Web. 11 Apr. 2013.http://www.brighamandwomens.org/Departments_and_Services/medicine/services/sleepmedicine/Default.aspx
  5. "MCB 186. Circadian Biology: From Cellular Oscillators to Sleep Regulation." Harvard: FAS Registrar's Office. The President and Fellows of Harvard College, n.d. Web. 11 Apr. 2013.Web site: MCB 186. Circadian Biology: From Cellular Oscillators to Sleep Regulation | FAS Registrar's Office . 2013-04-13 . https://web.archive.org/web/20150610215808/http://www.registrar.fas.harvard.edu/courses-exams/course-catalog/mcb-186-circadian-biology-cellular-oscillators-sleep-regulation . 2015-06-10 .
  6. Czeisler . C. A. . Weitzman . E. d . Moore-Ede . M. C. . Zimmerman . J. C. . Knauer . R. S. . 1980-12-12 . Human sleep: its duration and organization depend on its circadian phase . Science . 210 . 4475 . 1264–1267 . 10.1126/science.7434029 . 0036-8075 . 7434029.
  7. Joseph S. Takahashi, Hee-Kyung Hong, Caroline H. Ko & Erin L. McDearmon "The genetics of mammalian circadian order and disorder: implications for physiology and disease" Nature Reviews Genetics 9, 764-775 (October 2008)http://www.nature.com/nrg/journal/v9/n10/full/nrg2430.html
  8. Czeisler . C. A. . Allan . J. S. . Strogatz . S. H. . Ronda . J. M. . Sánchez . R. . Ríos . C. D. . Freitag . W. O. . Richardson . G. S. . Kronauer . R. E. . 1986-08-08 . Bright light resets the human circadian pacemaker independent of the timing of the sleep-wake cycle . Science . 233 . 4764 . 667–671 . 10.1126/science.3726555 . 0036-8075 . 3726555.
  9. Czeisler . C. A. . Kronauer . R. E. . Allan . J. S. . Duffy . J. F. . Jewett . M. E. . Brown . E. N. . Ronda . J. M. . 1989-06-16 . Bright light induction of strong (type 0) resetting of the human circadian pacemaker . Science . 244 . 4910 . 1328–1333 . 10.1126/science.2734611 . 0036-8075 . 2734611.
  10. Klein . Torsten . Martens . Heinz . Dijk . Derk-Jan . Kronauer . Richard E. . Seely . Ellen W. . Czeisler . Charles A. . June 1993 . Circadian Sleep Regulation in the Absence of Light Perception: Chronic Non-24-Hour Circadian Rhythm Sleep Disorder in a Blind Man With a Regular 24-Hour Sleep—Wake Schedule . Sleep . 16 . 4 . 333–343 . 10.1093/sleep/16.4.333 . 8341894 . 1550-9109.
  11. Czeisler . Charles A. . Shanahan . Theresa L. . Klerman . Elizabeth B. . Martens . Heinz . Brotman . Daniel J. . Emens . Jonathan S. . Klein . Torsten . Rizzo . Joseph F. . 1995-01-05 . Suppression of Melatonin Secretion in Some Blind Patients by Exposure to Bright Light . New England Journal of Medicine . 332 . 1 . 6–11 . 10.1056/nejm199501053320102 . 7990870 . 0028-4793. free .
  12. Yamazaki S, Goto M, Menaker M . 1999 . No Evidence for Extraocular Photoreceptors in the Circadian System of the Syrian Hamster . Journal of Biological Rhythms . 14 . 3. 197–201 . 10.1177/074873099129000605. 10452331 . 2102758 .
  13. Münch M, Bromundt V . Dec 2012 . Light and chronobiology: implications for health and disease . Dialogues in Clinical Neuroscience . 14 . 4 . 448–53 . 10.31887/DCNS.2012.14.4/mmuench . 3553574 . 23393421.
  14. Higuchi S, Hida A, Tsujimura S, Mishima K, Yasukouchi A, Lee SI, Kinjyo Y, Miyahira M. 2013 . Melanopsin Gene Polymorphism I394T Is Associated with Pupillary Light Responses in a Dose-Dependent Manner . PLOS ONE . 8 . 3 . e60310 . 10.1371/journal.pone.0060310 . 23555953 . 3610661. 2013PLoSO...860310H . free .
  15. Wright . Kenneth P. . Czeisler . Charles A. . 2002-07-26 . Absence of Circadian Phase Resetting in Response to Bright Light Behind the Knees . Science . 297 . 5581 . 571 . 10.1126/science.1071697 . 12142528 . 12121143 . 0036-8075.
  16. Möller-Levet CS, Archer SN, Bucca G, Laing EE, Slak A, Kabiljo R, Lo JC, Santhi N, von Schantz M, Smith CP, Dijk DJ. Mar 2013 . Effects of insufficient sleep on circadian rhythmicity and expression amplitude of the human blood transcriptome . Proc. Natl. Acad. Sci. USA . 110 . 12 . E1132–41 . 10.1073/pnas.1217154110 . 23440187 . 3607048. free .
  17. "Annual Sleep in American Poll Exploring Connections with Communications Technology Use and Sleep". National Sleep Foundation. March 7, 2011.http://www.sleepfoundation.org/article/press-release/annual-sleep-america-poll-exploring-connections-communications-technology-use-
  18. Chang . Anne-Marie . Aeschbach . Daniel . Duffy . Jeanne F. . Czeisler . Charles A. . 2015-01-27 . Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness . Proceedings of the National Academy of Sciences . en . 112 . 4 . 1232–1237 . 10.1073/pnas.1418490112 . 0027-8424 . 4313820 . 25535358 . free .
  19. Li MD, Li CM, Wang Z. Sep 2012 . The role of circadian clocks in metabolic disease . Yale J Biol Med . 85 . 3 . 387–401 . 3447202 . 23012586.
  20. Kavarana MN, Sade RM. May 2012 . Ethical issues in cardiac surgery . Future Cardiology . 8 . 3 . 451–65 . 10.2217/fca.11.91 . 3374583 . 22642634.
  21. "Sleep disorders linked to poor health and reduced occupational performance in police officers". National Sleep Foundation. Jan 3, 2012 http://www.sleepfoundation.org/alert/sleep-disorders-linked-poor-health-and-reduced-occupational-performance-police-officers
  22. Web site: Charles A. Czeisler . 2023-08-08 . scholar.google.com.
  23. Czeisler . Charles A. . Weitzman . Elliot D. . Moore-Ede . Martin C. . Zimmerman . Janet C. . Knauer . Richard S. . 1980-12-12 . Human Sleep: Its Duration and Organization Depend on Its Circadian Phase . Science . 210 . 4475 . 1264–1267 . 10.1126/science.7434029 . 7434029 . 0036-8075.
  24. Weitzman . Elliot D. . Czeisler . Charles A. . Coleman . Richard M. . Spielman . Arthur J. . Zimmerman . Janet C. . Dement . William . Pollak . Charles P. . 1981-07-01 . Delayed Sleep Phase Syndrome: A Chronobiological Disorder With Sleep-Onset Insomnia . Archives of General Psychiatry . 38 . 7 . 737–746 . 10.1001/archpsyc.1981.01780320017001 . 7247637 . 0003-990X.
  25. Czeisler . Charles A. . Allan . James S. . Strogatz . Steven H. . Ronda . Joseph M. . Sánchez . Ramiro . Ríos . C. David . Freitag . Walter O. . Richardson . Gary S. . Kronauer . Richard E. . 1986-08-08 . Bright Light Resets the Human Circadian Pacemaker Independent of the Timing of the Sleep-Wake Cycle . Science . 233 . 4764 . 667–671 . 10.1126/science.3726555 . 3726555 . 0036-8075.
  26. Czeisler . Charles A. . Kronauer . Richard E. . Allan . James S. . Duffy . Jeanne F. . Jewett . Megan E. . Brown . Emery N. . Ronda . Joseph M. . 1989-06-16 . Bright Light Induction of Strong (Type 0) Resetting of the Human Circadian Pacemaker . Science . 244 . 4910 . 1328–1333 . 10.1126/science.2734611 . 2734611 . 0036-8075.
  27. Ca . Czeisler . Tl . Shanahan . Eb . Klerman . H . Martens . Dj . Brotman . Js . Emens . T . Klein . Jf . Rizzo . 1995-01-05 . Suppression of melatonin secretion in some blind patients by exposure to bright light . The New England Journal of Medicine . en . 332 . 1 . 6–11 . 10.1056/NEJM199501053320102 . 0028-4793 . 7990870. free .
  28. Boivin . D. B. . Duffy . J. F. . Kronauer . R. E. . Czeisler . C. A. . 1996-02-08 . Dose-response relationships for resetting of human circadian clock by light . Nature . 379 . 6565 . 540–542 . 10.1038/379540a0 . 0028-0836 . 8596632. 4307825 .
  29. 10381883 . 284 . 5423 . Stability, precision, and near-24-hour period of the human circadian pacemaker. . June 1999 . Science . 2177–81 . 10.1126/science.284.5423.2177 . Czeisler CA, Duffy JF, Shanahan TL, Brown EN, Mitchell JF, Rimmer DW, Ronda JM, Silva EJ, Allan JS, Emens JS, Dijk DJ, Kronauer RE. 8516106 .
  30. Post, Sarah. "Bright Light behind the Knees Is Just Bright Light behind the Knees." Genome News Network. Craig Venter Institute, 16 Aug. 2002. Web. 22 Apr. 2013.http://www.genomenewsnetwork.org/articles/08_02/bright_knees.shtml
  31. Campbell, Scott S., and Patricia S. Murphy. "Extraocular Circadian Phototransduction in Humans." Science. American Association for the Advancement of Science, 16 Jan. 1998. Web. 23 Apr. 2013.https://www.science.org/doi/abs/10.1126/science.279.5349.396
  32. Lockley . Steven W. . Cronin . John W. . Evans . Erin E. . Cade . Brian E. . Lee . Clark J. . Landrigan . Christopher P. . Rothschild . Jeffrey M. . Katz . Joel T. . Lilly . Craig M. . Stone . Peter H. . Aeschbach . Daniel . Czeisler . Charles A. . Harvard Work Hours, Health and Safety Group . 2004-10-28 . Effect of reducing interns' weekly work hours on sleep and attentional failures . The New England Journal of Medicine . 351 . 18 . 1829–1837 . 10.1056/NEJMoa041404 . 1533-4406 . 15509816. free .
  33. Landrigan . Christopher P. . Rothschild . Jeffrey M. . Cronin . John W. . Kaushal . Rainu . Burdick . Elisabeth . Katz . Joel T. . Lilly . Craig M. . Stone . Peter H. . Lockley . Steven W. . Bates . David W. . Czeisler . Charles A. . 2004-10-28 . Effect of reducing interns' work hours on serious medical errors in intensive care units . The New England Journal of Medicine . 351 . 18 . 1838–1848 . 10.1056/NEJMoa041406 . 1533-4406 . 15509817. free .
  34. Barger . Laura K. . Cade . Brian E. . Ayas . Najib T. . Cronin . John W. . Rosner . Bernard . Speizer . Frank E. . Czeisler . Charles A. . Harvard Work Hours, Health, and Safety Group . 2005-01-13 . Extended work shifts and the risk of motor vehicle crashes among interns . The New England Journal of Medicine . 352 . 2 . 125–134 . 10.1056/NEJMoa041401 . 1533-4406 . 15647575. free .
  35. Czeisler . Charles A. . Walsh . James K. . Roth . Thomas . Hughes . Rod J. . Wright . Kenneth P. . Kingsbury . Lilliam . Arora . Sanjay . Schwartz . Jonathan R. L. . Niebler . Gwendolyn E. . Dinges . David F. . U.S. Modafinil in Shift Work Sleep Disorder Study Group . 2005-08-04 . Modafinil for excessive sleepiness associated with shift-work sleep disorder . The New England Journal of Medicine . 353 . 5 . 476–486 . 10.1056/NEJMoa041292 . 1533-4406 . 16079371. free .
  36. Duffy . Jeanne F. . Cain . Sean W. . Chang . Anne-Marie . Phillips . Andrew J. K. . Münch . Mirjam Y. . Gronfier . Claude . Wyatt . James K. . Dijk . Derk-Jan . Wright . Kenneth P. . Czeisler . Charles A. . 2011-09-13 . Sex difference in the near-24-hour intrinsic period of the human circadian timing system . Proceedings of the National Academy of Sciences of the United States of America . 108 . Suppl 3 . 15602–15608 . 10.1073/pnas.1010666108 . 1091-6490 . 3176605 . 21536890 . free .
  37. Buxton . Orfeu M. . Cain . Sean W. . O’Connor . Shawn P. . Porter . James H. . Duffy . Jeanne F. . Wang . Wei . Czeisler . Charles A. . Shea . Steven A. . 2012-04-11 . Adverse Metabolic Consequences in Humans of Prolonged Sleep Restriction Combined with Circadian Disruption . Science Translational Medicine . en . 4 . 129 . 129ra43 . 10.1126/scitranslmed.3003200 . 1946-6234 . 3678519 . 22496545.
  38. Chang . Anne-Marie . Aeschbach . Daniel . Duffy . Jeanne F. . Czeisler . Charles A. . 2015-01-27 . Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness . Proceedings of the National Academy of Sciences of the United States of America . 112 . 4 . 1232–1237 . 10.1073/pnas.1418490112 . 1091-6490 . 4313820 . 25535358 . free .
  39. "Human Biological Clock Set Back an Hour." Human Biological Clock Set Back an Hour. N.p., n.d. Web. 24 Apr. 2013.
  40. Ortiz, Maria B. "To Sleep, Perchance to Win." ESPN. ESPN Internet Ventures, 4 December 2009. Web. 23 April 2013.
  41. Flannery, Paul. "Person of Interest: Charles Czeisler." Boston Magazine. Metrocorp Inc., May 2011. Web. 22 Apr. 2013.
  42. Czeisler, Charles. "Sleep Deficit: The Performance Killer A Conversation with Charles A. Czeisler by Bronwyn Fryer." Harvard Business Review. Bronwyn Fryer. Boston: Harvard Business Review, October 2006.
  43. "Past Presidents." Past Sleep Research Society Presidents. N.p., n.d. Web. 13 Apr. 2013. http://www.sleepresearchsociety.org/pastpresidents.aspx
  44. "Resident Work Hours." - Past SRS Government Relations Initiative. N.p., n.d. Web. 13 Apr. 2013. http://www.sleepresearchsociety.org/residentworkhours.aspx
  45. Web site: Chadra. Karen. NSC Announces Winners of its Prestigious Green Cross for Safety Awards. 2020-06-19. National Safety Council. en-US.
  46. Czeisler . Charles A. . 2018-07-12 . Housing Immigrant Children - The Inhumanity of Constant Illumination . The New England Journal of Medicine . 379 . 2 . e3 . 10.1056/NEJMp1808450 . 1533-4406 . 29932841. 49384225 .
  47. https://sleep.med.harvard.edu/people/faculty/210/ Charles Czeisler Profile
  48. "Aschoff's Rule." Society for Research on Biological Rhythms. N.p., n.d. Web. 24 Apr. 2013.http://www.srbr.org/Documents/5link_Aschoff%27s_rule_history%202007a_2008-04-22.doc
  49. "NIOSH to Seek Applications for 2006 Director's Award." Centers for Disease Control and Prevention. Centers for Disease Control and Prevention, n.d. Web. 13 Apr. 2013. https://www.cdc.gov/niosh/enews/enewsV4N5.html
  50. "Call For Nominations: National Sleep Foundation's 2014 Lifetime Achievement Award." National Sleep Foundation. N.p., n.d. Web. 13 Apr. 2013. http://www.sleepfoundation.org/alert/call-nominations-national-sleep-foundation%E2%80%99s-2014-lifetime-achievement-award
  51. http://www.rsm.ac.uk/academicboard/downloads/agenda-papers07-10.pdf
  52. http://www.sleepresearchsociety.org/distinguishedscientist.aspx "Distinguished Scientist Award." SRS. N.p., n.d. Web. 13 Apr. 2013
  53. "Charles Czeisler of BWH Receives Public Policy Award from American Academy of Sleep Medicine" AASM. N.p., n.d. Web. 13 Apr. 2013. http://www.aasmnet.org/Articles.aspx?id=1765
  54. Web site: Farrell Prize in Sleep Medicine Division of Sleep Medicine @ Harvard Medical School. 2020-06-19. sleep.med.harvard.edu.
  55. Web site: 2019 Alumni Awards. 2020-06-19. Alumni Association. en.

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