Shift work effects millions of people and many experience serious health-related consequences, such as shortened and disrupted sleep, fatigue, impaired performance, and gastrointestinal disturbances. Night shift workers experience these symptoms because their internal circadian rhythms rarely phase shift to align with the new (daytime) sleep schedule. One reason it is so difficult for these individuals to shift is that they continue to be exposed to the natural 24-hour light-dark cycle, a very powerful zeitgeber that works to keep rhythms synchronized for alertness during the day and sleep at night. One strategy for shift work adaptation is to force the circadian pacemaker (clock) to phase shift to realign with shifted sleep-wake schedules, while another approach is to try to improve shift worker's daytime sleep and nighttime performance without shifting rhythms. Melatonin is a hormone normally secreted by the pineal gland at night. Previous studies suggest that exogenously-administered melatonin has phase-shifting as well as sedative effects. In Study 1, the investigator will determine whether appropriately-timed melatonin can phase shift the circadian pacemaker to align with a 9-hour shift of the sleep-wake schedule in subjects who do simulated night work and are exposed to the natural 24-hour light-dark cycle and other zeitgebers. Phase shifts will be assessed using phase measures derived from endogenous melatonin secretion and core body temperature. In Study 2, the investigator will investigate the immediate effects of two different doses of melatonin on daytime sleep after simulated night work, and assess the effects of melatonin treatment on nighttime performance. Sleep will be polygraphically-recorded to assess changes to sleep architecture, and multiple sleep latency tests and computerized performance tests will be performed during the night shifts to assess alertness.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
1R01NS035695-01A1
Application #
2399219
Study Section
Clinical Neuroscience and Biological Psychopathology Review Committee (CNBP)
Program Officer
Kitt, Cheryl A
Project Start
1997-08-01
Project End
2001-05-31
Budget Start
1997-08-01
Budget End
1998-05-31
Support Year
1
Fiscal Year
1997
Total Cost
Indirect Cost
Name
Rush University Medical Center
Department
Type
DUNS #
City
Chicago
State
IL
Country
United States
Zip Code
60612
Smith, Mark R; Eastman, Charmane I (2012) Shift work: health, performance and safety problems, traditional countermeasures, and innovative management strategies to reduce circadian misalignment. Nat Sci Sleep 4:111-32
Burgess, Helen J; Fogg, Louis F (2008) Individual differences in the amount and timing of salivary melatonin secretion. PLoS One 3:e3055
Burgess, Helen J; Eastman, Charmane I (2004) Early versus late bedtimes phase shift the human dim light melatonin rhythm despite a fixed morning lights on time. Neurosci Lett 356:115-8
Sharkey, Katherine M; Eastman, Charmane I (2002) Melatonin phase shifts human circadian rhythms in a placebo-controlled simulated night-work study. Am J Physiol Regul Integr Comp Physiol 282:R454-63
Burgess, Helen J; Sharkey, Katherine M; Eastman, Charmane I (2002) Bright light, dark and melatonin can promote circadian adaptation in night shift workers. Sleep Med Rev 6:407-20
Hebert, Marc; Martin, Stacia K; Lee, Clara et al. (2002) The effects of prior light history on the suppression of melatonin by light in humans. J Pineal Res 33:198-203
Martin, Stacia K; Eastman, Charmane I (2002) Sleep logs of young adults with self-selected sleep times predict the dim light melatonin onset. Chronobiol Int 19:695-707
Sharkey, K M; Fogg, L F; Eastman, C I (2001) Effects of melatonin administration on daytime sleep after simulated night shift work. J Sleep Res 10:181-92
Baehr, E K; Revelle, W; Eastman, C I (2000) Individual differences in the phase and amplitude of the human circadian temperature rhythm: with an emphasis on morningness-eveningness. J Sleep Res 9:117-27