Initial steps towards a circadian compromise for night shift workers.
Lee C; Eastman CI
Proceedings of the 9th meeting of the Society for Research on Biological Rhythms, June 23-26, 2004, Whistler, British Columbia. Urbana, IL: Society for Research on Biological Rhythms, 2004 Jun; :33-34
This is the first installment of a multi-part study to determine if circadian adaptation (re-alignment of the temperature minimum (Tmin) to within daytime sleep) can be achieved and maintained while alternating between working night shifts and having days off. Subjects were required to sleep from 23:00 to 07:00 (and up to 1 h later on weekends) for 3 weeks. Following this baseline period, they worked 2 consecutive simulated night shifts (23:00Ð07:00). Experimental subjects (n=11) received five 15-minute intermittent bright light pulses (approximately 3500 lux; approximately 2200 microW/cm2) during the night shift, wore sunglasses (approximately 12% transmission) while traveling home, and slept in the dark (08:30Ð15:30) after each night shift. Control subjects (n=8) received ordinary room light (approximately 20 lux) throughout the night shift, wore sunglasses (approximately 37% transmission), and slept whenever they wanted after the night shifts. The Tmin (dim light melatonin onset + 7 h) was determined before and after the night shifts. Tmins (mean +/- SD in h) for the experimental subjects were 04:24 +/- 0.8 and 7:36 +/- 1.4, respectively; for control subjects, they were 04:00 +/- 1.2 and 4:36 +/- 1.4. Thus far, the experimental treatment phase delayed the Tmin by 1.6 h/day. After one more night shift, we expect the Tmin to delay to within daytime sleep. Given a fairly late sleep schedule on days off, this phase position would be an ideal compromise between working nights and having days off.
Circadian-rhythms; Work-environment; Workers; Sleep-deprivation; Sleep-disorders; Stimulants; Work-intervals; Exposure-levels; Statistical-analysis
Proceedings of the 9th meeting of the Society for Research on Biological Rhythms, June 23-26, 2004, Whistler, British Columbia
Rush University Medical Center, Chicago, Illinois