Charles Czeisler

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Charles Czeisler
Chicago, Illinois
ResidenceUnited States
Alma materUndergraduate: Harvard College
M.D./Ph.D.: Stanford University
Known forHuman sleep medicine
Circadian rhythm research
AwardsAschoff's Rule

National Sleep Foundation: Lifetime Achievement Award

Royal College of London: Adrian Gold Medal
Scientific career
FieldsChronobiology, neurobiology, sleep medicine
Academic advisorsWilliam C. Dement
Elliot D. Weitzman
WebsiteHarvard Neuroscience faculty page
Harvard Medical School faculty profile

Charles A. Czeisler (born 1952) is an American physician and sleep researcher.[1] He is a researcher and author in the fields of both circadian rhythms and sleep medicine.

Background and education[edit]

Czeisler graduated from Harvard College, magna cum laude in 1974, with a degree in Biochemistry and Molecular Biology. He received his Ph.D. in Neuro- and Bio-behavioral Sciences and his M.D. from Stanford University.[2] His undergraduate thesis was focused on cortisol timing release.[3] As a graduate student at Stanford, Czeisler continued his research in Dr. William Dement's lab.[2][3] Elliot Weitzman, who both worked with and mentored Czeisler, influenced Czeisler to study sleep.[2][3] 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.[2][4]

Czeisler has spent over 30 years researching the relationship between human sleep and the physiology of the human circadian clock and teaching a course at Harvard College on Circadian Biology for undergraduate and graduate students.[2][5] 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 Institute 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.[2]

Family life[edit]

Dr. Czeisler was one of Tibor Czeisler and Wanda Victoria Murzyn's three children.[1] In 1993, Czeisler married Theresa Lynn Shanahan M.D. They now have three children and live in the Boston area.[1] In his free time, Czeisler enjoys swimming, playing tennis, and slalom water skiing.[1]

Research interests[edit]

Czeisler’s research focus is the neurobiology of human circadian rhythm. He examines the relationship between the circadian oscillator and sleep homeostasis, and how this interaction affects health.[6][7] Czeisler's research interests encompass many areas including body temperature rhythms [8] and the effects of melatonin on humans (2011).[9]

Czeisler investigates how the physiological system works to reset the circadian pacemaker.[7] His team discovered that light transduced by non-visual input (melanopsin activation) could reset the circadian clock in patients without sight.[9] This indicated that some blind humans can entrain to light through non-visual photoreceptors (2007).[9][10] 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.[11] Significantly, this challenged the misconception that rod and cone photoreceptors were the sole receptors for photo-entrainment in humans.[9][12] In 2002, Czeisler published a study that defended the long-held notion that mammals do not have extra-occular photoreceptors.[13][14] The findings of his study definitively refute those of the famous 1998 Science publication, “Extraocular Circadian Phototransduction in Humans,” which found that bright light behind the knees can help regulated human circadian photoentrainment.[13][14]

Czeisler has examined the effects of sleep deprivation on the sleep-wake cycle and circadian rhythms, and how this impacts attention performance.[7][15] He found that bright light duration impacts the circadian pacemaker, melatonin suppression, and sleepiness.[6][9] He has also discovered that even room lighting can suppress melatonin production and its duration.[6] Currently (2012), Czeisler is examining the effects of light timing, duration, intensity, and wavelength on resetting the pacemaker through ipRGCs, which contain the photopigment melanopsin.[9][12]

Czeisler’s work has many important applications. He showed that sleep deprivation could have adverse consequences affecting obesity and diabetes, among other health problems.[6][9][16] He has also investigated the effects of chronic sleep deprivation and restriction, night shifts, and circadian disruption, on neurobehavioral performance and metabolism.[7][9][16][17] Furthermore, Czeisler studied how sleep deprivation impairs the psychomotor performance of night shift workers (2009-2014),[6] specifically surgeons (2009-2013)[17] and residents (2010), police officers (2004-2008),[18] 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.[6] Czeisler’s research can be applied to medicine, space travel, and night occupations including shift-work.[7][17]

Summary of selected contributions[edit]

  • 1990 – Human circadian clock is highly light sensitive.[19]
  • 1995 – Blind people can still retain sleep rhythms if their eyes remain intact.[20]
  • 1999 - Determined that the average circadian period in humans is 24.18 hours, not over 25 hours as previously thought.[21]
  • 2002 – Invalidated findings that bright light behind the knees can impact human circadian rhythms.[13][14]
  • 2006 – Melatonin supplementation during the day can improve sleep quality at night and can be helpful to shift workers, people with jet-lag[22] as well as people with circadian rhythm sleep disorders.
  • 2006 - Task performance while chronically sleep deprived suffers severely.[23]
  • 2013 – Sleep deprivation causes changes in normal gene expression and can negatively impact health.[24]

Sleep health and occupational safety[edit]

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.”[25] 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 and Portland Trail Blazers for the National Basketball Association (NBA), he emphasized sleep as the “third pillar of health” alongside nutrition and exercise.[26] 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.[26][27]

According to Czeisler, sleep deficit 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.[28]

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.[2][29][30] 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.[2]

A complete listing of agencies to which Czeisler has consulted can be found at his Harvard Faculty Profile.

Honors and awards[edit]

Czeisler has earned numerous accolades and awards since 1991 for his research in sleep medicine as well as his professional advocacy for improving occupational health and safety. A few noteworthy honors include:

A more complete list of these awards can be found on his Harvard Faculty Profile


  1. ^ a b c d Czeisler, Charles A. E-mail interview. 24 April 2013.
  2. ^ a b c d e f g h i j k l m "Faculty Profile: Charles A. Czeisler, PhD, MD, FRCP." Division of Sleep Medicine: Harvard Medical School. Harvard College, n.d. Web. 10 Apr. 2013.[1]
  3. ^ a b c "Charles Czeisler." Interview. The Science Network. N.p., June 2009. Web. 23 Apr. 2013. <>
  4. ^ "Division of Sleep Medicine." Brigham and Women's Hospital. The Division of Sleep Medicine, 25 Jan. 2013. Web. 11 Apr. 2013.[2]
  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."Archived copy". Archived from the original on 2015-06-10. Retrieved 2013-04-13.
  6. ^ a b c d e f "Annual Sleep in American Poll Exploring Connections with Communications Technology Use and Sleep". National Sleep Foundation. March 7, 2011.[3]
  7. ^ a b c d e 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)[4]
  8. ^ Czeisler CA, Weitzman Ed Moore-Ede MC, Zimmerman JC, Knauer RS (Dec 1980). "Human sleep: its duration and organization depend on its circadian phase". Science. 210 (4475): 1264–7. doi:10.1126/science.7434029. PMID 7434029.
  9. ^ a b c d e f g h Münch M, Bromundt V (Dec 2012). "Light and chronobiology: implications for health and disease". Dialogues Clinical Neuroscience. 14 (4): 448–53.
  10. ^ Wahnschaffe A, Haedel S, Rodenbeck A, Stoll C, Rudolph H, Kozakov R, Schoepp H, Kunz D (Jan 2013). "Out of the lab and into the bathroom: evening short-term exposure to conventional light suppresses melatonin and increases alertness perception". Int J Mol Sci. 14 (2): 2573–89. doi:10.3390/ijms14022573. PMC 3588003. PMID 23358248.
  11. ^ Yamazaki Shin, Goto Maki, Menaker Michael (1999). "No Evidence for Extraocular Photoreceptors in the Circadian System of the Syrian Hamster". Journal of Biological Rhythms. 14: 197–201. doi:10.1177/074873099129000605.
  12. ^ a b 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. doi:10.1371/journal.pone.0060310. PMC 3610661. PMID 23555953.
  13. ^ a b c 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.[5]
  14. ^ a b c 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.[6]
  15. ^ 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. doi:10.1073/pnas.1217154110. PMC 3607048. PMID 23440187.
  16. ^ a b Li MD, Li CM, Wang Z (Sep 2012). "The role of circadian clocks in metabolic disease". Yale J Biol Med. 85 (3): 387–401. PMC 3447202. PMID 23012586.
  17. ^ a b c Kavarana MN, Sade RM (May 2012). "Ethical issues in cardiac surgery". Future Cardiology. 8 (3): 451–65. doi:10.2217/fca.11.91. PMC 3374583. PMID 22642634.
  18. ^ "Sleep disorders linked to poor health and reduced occupational performance in police officers". National Sleep Foundation. Jan 3, 2012 [7]
  19. ^ Strogatz, Steven H. "Interpreting the Human Phase Response Curve to Multiple Bright-Light Exposures." Journal of Biological Rhythms. SAGE Publications, June 1990. Web. 23 Apr. 2013.[8]
  20. ^ Hanley, Daniel Q. "Blind People's Eyes May Serve Purpose in Regulating Sleep." Associated Press Archives. Associated Press, 05 Jan. 1995. Web. 23 Apr. 2013.[9]
  21. ^ Czeisler CA, Duffy JF, Shanahan TL, Brown EN, Mitchell JF, Rimmer DW, Ronda JM, Silva EJ, Allan JS, Emens JS, Dijk DJ, Kronauer RE (June 1999). "Stability, precision, and near-24-hour period of the human circadian pacemaker". Science. 284: 2177–81. doi:10.1126/science.284.5423.2177. PMID 10381883.
  22. ^ Smith, Michael. "Melatonin Gets Nod for Shift Workers and Jet-Lagged." Medpage Today. Everyday Health, 1 May 2006. Web. 21 Apr. 2013.[10]
  23. ^ "Sleep Deficit: The Performance Killer." Interview by Bronwyn Fryer. Harvard Business Review. Harvard Business School Publishing, Oct. 2006. Web. 24 Apr. 2013. <>[11]
  24. ^ Brown, Eryn. "Sleep Deprivation Has Genetic Consequences, Study Finds." Los Angeles Times. Los Angeles Times, 01 Mar. 2013. Web. 24 Apr. 2013.[12]
  25. ^ "Human Biological Clock Set Back an Hour." Human Biological Clock Set Back an Hour. N.p., n.d. Web. 24 Apr. 2013.
  26. ^ a b Ortiz, Maria B. "To Sleep, Perchance to Win." ESPN. ESPN Internet Ventures, 4 December 2009. Web. 23 April 2013.
  27. ^ Flannery, Paul. "Person of Interest: Charles Czeisler." Boston Magazine. Metrocorp Inc., May 2011. Web. 22 Apr. 2013.
  28. ^ 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.
  29. ^ "Past Presidents." Past Sleep Research Society Presidents. N.p., n.d. Web. 13 Apr. 2013. [13]
  30. ^ "Resident Work Hours." - Past SRS Government Relations Initiative. N.p., n.d. Web. 13 Apr. 2013. [14]
  31. ^ "Aschoff's Rule." Society for Research on Biological Rhythms. N.p., n.d. Web. 24 Apr. 2013.[15][permanent dead link]
  32. ^ "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. [16]
  33. ^ "Call For Nominations: National Sleep Foundation's 2014 Lifetime Achievement Award." National Sleep Foundation. N.p., n.d. Web. 13 Apr. 2013. [17] Archived 2013-04-06 at the Wayback Machine.
  34. ^ [18][permanent dead link]
  35. ^ "Distinguished Scientist Award." SRS. N.p., n.d. Web. 13 Apr. 2013
  36. ^ "Charles Czeisler of BWH Receives Public Policy Award from American Academy of Sleep Medicine" AASM. N.p., n.d. Web. 13 Apr. 2013. [19]