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Charles A. Czeisler is a researcher and author in the fields of both circadian rhythms and sleep medicine. He holds both an M.D. and a Ph.D. and is currently the Chief and Director of the Division of Sleep Medicine at Harvard Medical School (http://hms.harvard.edu/hms/home.asp) as well as Brigham and Women's Hospital (http://www.brighamandwomens.org/) in Boston, MA, USA. He has published many scientific articles on how the sleep homeostat interacts with the circadian drive to sleep. He is concerned about safety issues caused by sleep deprivation, particularly reduced job performance among drivers of vehicles and medical professionals.

He is known internationally for his research in human sleep and physiology of circadian rhythms (12). Czeisler’s research focus is the neurobiology of the human circadian rhythm & Per, which is found in the suprachiasmatic nucleus (SCN) in the hypothalamus. He examines the relationship between the circadian oscillator and sleep homeostasis, and how this interaction affects one’s health. Czeisler specifically investigates how the pineal hormone, melatonin, influences rhythms of sleep and circadian oscillation (9).

He investigates how the physiological system works to reset the circadian pacemaker. His team discovered that melatonin suppression could reset the circadian clock in patients without sight. This indicated that even in blind patients, photoreceptors exist that enable entrainment to light. (2) 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. Significantly, this challenged the misconception that rod and cone photoreceptors were the sole receptors for photo-entrainment in humans.

Ceizler has examined the effects of sleep deprivation on the sleep-wake cycle and circadian rhythms, and how this thus impacts visual attention performance. (1) He found that bright light duration impacts circadian pacemaker, melatonin suppression, and sleepiness. (4) Czeisler has also discovered that even room lighting can suppress melatonin production and its duration. (6) Currently, Czeisler is examining the affects of light timing, duration, intensity, and wavelength on resetting the pacemaker through ipRGCs, which contain the photopigment melanopsin. (7).

Czeisler’s work has many important applications. He showed that sleep deprivation could have adverse consequences like health problems including obesity, diabetes, among others (10). He has also investigated the effects of sleep restriction, night shifts, and circadian disruption, on neurobehavioral performance and metabolism (5). Furthermore, Czeisler studied how sleep deprivation impairs the psychomotor performance of doctors and night workers (11). Other research interests of his include studying wakefulness, sleep deprivation and how it can be prevented, and influences on the clock like exercise and age. Czeisler’s research can be applied to medicine, space travel, and night occupations including shift-work. (8)

Selected articles can be found on his webpage: http://sleep.med.harvard.edu/people/faculty/210/Charles+A+Czeisler+PhD+MD+FRCP

A more complete list can be found on Pubmed (search "Czeisler CA" or "Czeisler Circadian"): http://www.ncbi.nlm.nih.gov/sites/entrez

Category:Harvard University faculty Category:Living people Category:American physicians Category:Sleep researchers

Citations

1. Pomplun M, Silva EJ, Ronda JM, Cain SW, Münch MY, Czeisler CA, Duffy JF. The effects of circadian phase, time awake, and imposed sleep restriction on performing complex visual tasks: evidence from comparative visual search. J Vis. 2012 Jul 26;12(7). [ ]

2. Zaidi, Farhan H. ,1,8 Joseph T. Hull,2,8 Stuart N. Peirson,3,8 Katharina Wulff,3 Daniel Aeschbach,2,4 Joshua J. Gooley,2,4 George C. Brainard,5 Kevin Gregory-Evans,1 Joseph F. Rizzo, III,6 Charles A. Czeisler,2,4 Russell G. Foster,3, Merrick J. Moseley,7,   and Steven W. Lockley2,4,    Short-Wavelength Light Sensitivity of Circadian, Pupillary, and Visual Awareness in Humans Lacking an Outer Retina. Curr Biol. 2007 December 18; 17(24): 2122–2128.

3. Rüger M, St Hilaire MA, Brainard G, Khalsa SB, Kronauer RE, Czeisler CA, Lockley SW. Human phase response curve to a single 6.5-h pulse of short-wavelength light. J Physiol. 2012 Nov 26. [ ]

4. Chang AM, Santhi N, St Hilaire M, Gronfier C, Bradstreet DS, Duffy JF, Lockley SW, Kronauer RE, Czeisler CA. Human responses to bright light of different durations. J Physiol. 2012 Jul 1;590(Pt 13):3103-12 [ ]

5. Anderson C, Sullivan JP, Flynn-Evans EE, Cade BE, Czeisler CA, Lockley SW. Deterioration of neurobehavioral performance in resident physicians during repeated exposure to extended duration work shifts. Sleep. 2012 Aug 1;35(8):1137-46. [ ]

Buxton OM, Cain SW, O'Connor SP, Porter JH, Duffy JF, Wang W, Czeisler CA, Shea SA. Adverse metabolic consequences in humans of prolonged sleep restriction combined with circadian disruption. Sci Transl Med. 2012 Apr 11;4(129):129ra43. [ ]

6. Gooley JJ, Chamberlain K, Smith KA, Khalsa SB, Rajaratnam SM, Van Reen E, Zeitzer JM, Czeisler CA, Lockley SW. Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans. J Clin Endocrinol Metab. 2011 Mar;96(3):E463-72. Epub 2010 Dec 30. [ ]

7. Gooley JJ, Ho Mien I, St Hilaire MA, Yeo SC, Chua EC, van Reen E, Hanley CJ, Hull JT, Czeisler CA, Lockley SW. Melanopsin and rod-cone photoreceptors play different roles in mediating pupillary light responses during exposure to continuous light in humans. J Neurosci. 2012 Oct 10;32(41):14242-53. [ ]

8. Anderson C, Sullivan JP, Flynn-Evans EE, Cade BE, Czeisler CA, Lockley SW. Deterioration of neurobehavioral performance in resident physicians during repeated exposure to extended duration work shifts. Sleep. 2012 Aug 1;35(8):1137-46. [ ]

9. Dijk DJ, Duffy JF, Silva EJ, Shanahan TL, Boivin DB, Czeisler CA. Amplitude reduction and phase shifts of melatonin, cortisol and other circadian rhythms after a gradual advance of sleep and light exposure in humans. PLoS One. 2012;7(2):e30037 [ ]

10. Buxton OM, Cain SW, O'Connor SP, Porter JH, Duffy JF, Wang W, Czeisler CA, Shea SA. Adverse metabolic consequences in humans of prolonged sleep restriction combined with circadian disruption. Sci Transl Med. 2012 Apr 11;4(129):129ra43. [ ]

11. Nurok M, Czeisler CA, Lehmann LS. Sleep deprivation, elective surgical procedures, and informed consent. N Engl J Med. 2010 Dec 30;363(27):2577-9. [ ]

12. "Charles A. Czeisler Ph.D., M.D., FRCP: executive Profile & Biography" Business Week....