Combinations of Bright Light, Scheduled Dark, Sunglasses, and Melatonin to Facilitate Circadian Entrainment to Night Shift Work

Details

• Personal Author:
  Crowley SJ ; Eastman CI ; Fogg LF ; Lee C ; Tseng, Chih-Yu
• Description:
  Various combinations of interventions were used to phase-delay circadian rhythms to correct their misalignment with night work and day sleep. Young participants (median age = 22, n = 67) participated in 5 consecutive simulated night shifts (2300 to 0700) and then slept at home (0830 to 1530) in darkened bedrooms. Participants wore sunglasses with normal or dark lenses (transmission 15% or 2%) when outside during the day. Participants took placebo or melatonin (1.8 mg sustained release) before daytime sleep. During the night shifts, participants were exposed to a moving (delaying) pattern of intermittent bright light (approximately 5000 lux, 20 min on, 40 min off, 4-5 light pulses/night) or remained in dim light (approximately 150 lux). There were 6 intervention groups ranging from the least complex (normal sunglasses) to the most complex (dark sunglasses + bright light + melatonin). The dim light melatonin onset (DLMO) was assessed before and after the night shifts (baseline and final), and 7 h was added to estimate the temperature minimum (Tmin). Participants were categorized by their amount of reentrainment based on their final Tmin: not re-entrained (Tmin before the daytime dark/sleep period), partially re-entrained (Tmin during the first half of dark/sleep), or completely re-entrained (Tmin during the second half of dark/ sleep). The sample was split into earlier participants (baseline Tmin < or = 0700, sunlight during the commute home fell after the Tmin) and later participants (baseline Tmin > 0700). The later participants were completely re-entrained regardless of intervention group, whereas the degree of re-entrainment for the earlier participants depended on the interventions. With bright light during the night shift, almost all of the earlier participants achieved complete re-entrainment, and the phase delay shift was so large that darker sunglasses and melatonin could not increase its magnitude. With only room light during the night shift, darker sunglasses helped earlier participants phase-delay more than normal sunglasses, but melatonin did not increase the phase delay. The authors recommend the combination of intermittent bright light during the night shift, sunglasses (as dark as possible) during the commute home, and a regular, early daytime dark/sleep period if the goal is complete circadian adaptation to night-shift work. [Description provided by NIOSH]
• Subjects:
  Age Factors Aging Circadian Rhythm Demography Lighting Occupational Exposure Occupational Health Safety Shift Work Schedule Sleep Sleep Initiation And Maintenance Disorders

  More +
• Keywords:
  Age-factors Age-groups Circadian-rhythms Demographic-characteristics Humans Lighting-systems Occupational-exposure Shift-work Shift-workers Sleep-deprivation Sleep-disorders Workers

  More +
• ISSN:
  0748-7304
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article
• Place as Subject:
  Illinois ; OSHA Region 5
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  18
• Issue:
  6
• NIOSHTIC Number:
  nn:20029159
• Citation:
  J Biol Rhythms 2003 Dec; 18(6):513-523
• Contact Point Address:
  Biological Rhythms Research Laboratory, 1645W. Jackson, Suite 425, Chicago, IL 60612
• Email:
  ceastman@rush.edu
• Federal Fiscal Year:
  2004
• NORA Priority Area:
  Work Environment and Workforce: Organization of Work
• Performing Organization:
  Rush University Medical Center, Chicago, Illinois
• Peer Reviewed:
  True
• Start Date:
  19990930
• Source Full Name:
  Journal of Biological Rhythms
• End Date:
  20090430
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:953c7f3f81941bea0e646396ba75cdd1865c5326b7ad95e1608901534f9346014ccf5e430376640a9034248055777d0ea0b7397f6d10dcbbf80cce181598bb4a
• Download URL:
  https://stacks.cdc.gov/view/cdc/190211/cdc_190211_DS1.pdf
• File Type:
  [PDF - 98.76 KB ]