About 20 percent of U. S. workers have to work night shifts, resulting in serious consequences such as insomnia, fatigue, reduced alertness, impaired performance, gastrointestinal disturbances, and reduced job and public safety. These problems occur because the circadian clocks of the workers do not usually phase shift (reset) to adjust to the night work, day sleep schedule. Therefore, workers are forced to work during the """"""""wrong"""""""" phase of their circadian rhythms, when they are the most sleepy, inefficient, and prone to accidents, and to try to sleep during the day, again during the """"""""wrong"""""""" phase, which results in disrupted, shortened sleep and chronic sleep deprivation. We propose to test interventions which are designed to phase delay the circadian clock (set it later) so that circadian rhythms have a more appropriate phase relationship to night work and daytime sleep. These interventions will be tested in a simulated night shift protocol using a schedule which is common in nursing and industry (5 consecutive 8-hr night shifts). The interventions will be: 1) a very dark bedroom and a fixed 7-hr dark time for sleep at home after each night shift, 2) wearing dark goggles on the way home after night work, 3) taking melatonin at bedtime before daytime sleep and 4) intermittent bright light during the night shift. The interventions have been designed to take minimal effort by the subjects, so that they would be feasible for real shift workers, yet be strong enough to significantly improve night work performance and daytime sleep. Several combinations of these 4 interventions will be tested. The outcome measures will be: 1) circadian phase (from the circadian rhythm of endogenous melatonin secretion), 2) daytime sleep duration (from wrist activity monitors and sleep logs) and 3) night work sleepiness and performance (evaluated with a computer administered test battery). The goal is to advise shift workers and their employers about the relative benefits of the various combinations of interventions.

Agency
National Institute of Health (NIH)
Institute
National Institute for Occupational Safety and Health (NIOSH)
Type
Research Project (R01)
Project #
5R01OH003954-03
Application #
6446010
Study Section
Special Emphasis Panel (ZOH1-MJG (08))
Program Officer
Newhall, Jim
Project Start
1999-09-30
Project End
2002-09-29
Budget Start
2001-09-30
Budget End
2002-09-29
Support Year
3
Fiscal Year
2001
Total Cost
$286,000
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
Molina, Thomas A; Burgess, Helen J (2011) Calculating the dim light melatonin onset: the impact of threshold and sampling rate. Chronobiol Int 28:714-8
Canton, Jillian L; Smith, Mark R; Choi, Ho-Sun et al. (2009) Phase delaying the human circadian clock with a single light pulse and moderate delay of the sleep/dark episode: no influence of iris color. J Circadian Rhythms 7:8
Smith, Mark R; Fogg, Louis F; Eastman, Charmane I (2009) A compromise circadian phase position for permanent night work improves mood, fatigue, and performance. Sleep 32:1481-9
Smith, Mark R; Fogg, Louis F; Eastman, Charmane I (2009) Practical interventions to promote circadian adaptation to permanent night shift work: study 4. J Biol Rhythms 24:161-72
Burgess, Helen J; Fogg, Louis F (2008) Individual differences in the amount and timing of salivary melatonin secretion. PLoS One 3:e3055
Smith, Mark R; Cullnan, Erin E; Eastman, Charmane I (2008) Shaping the light/dark pattern for circadian adaptation to night shift work. Physiol Behav 95:449-56
Smith, Mark R; Eastman, Charmane I (2008) Night shift performance is improved by a compromise circadian phase position: study 3. Circadian phase after 7 night shifts with an intervening weekend off. Sleep 31:1639-45
Revell, Victoria L; Eastman, Charmane I (2005) How to trick mother nature into letting you fly around or stay up all night. J Biol Rhythms 20:353-65
Burgess, Helen J; Eastman, Charmane I (2005) The dim light melatonin onset following fixed and free sleep schedules. J Sleep Res 14:229-37

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