The research team revealed that use of light exposure therapy, dark sunglasses and a strict sleep schedule can help night-shift workers create a "compromise circadian phase position," which may result in increased performance and alertness during night shifts while still allowing adequate nighttime sleep on days off.
The study involved twenty-four healthy subjects with seven women and five men in both the experimental and control groups.
All subjects were young, but the experimental group was significantly older than the control group (average age of 28.9 years versus 23.7 years). Subjects did not work night shifts in the three months preceding the study and did not travel across more than three time zones in the month preceding the study.
During the research, subjects underwent a total of seven simulated night shifts from 11 p.m. to 7 a.m. with two days off. Experimental subjects slept in dark bedrooms at scheduled times: 8:30 a.m. to 3:30 p.m. after the first two night shifts, from 8:30 a.m. to 1:30 p.m. after the third night shifts, from 3 a.m. to 12 p.m. on the two weekend days off, and again from 8:30 a.m. to 3:30 p.m. after the final four night shifts.
They also were exposed to five, 15-minute, intermittent bright light pulses each night shift; wore dark sunglasses when outside; and received outdoor afternoon light exposure.
The performance of the experimental group was close to the level during day shifts, demonstrating fast reaction times with low variability and few or no lapses. In contrast, the control group continued to show longer and more variable reaction times on all night shifts.
The study suggests that in addition to adopting the recommended sleep pattern and wearing sunglasses, night-shift workers who use bright light exposure therapy will be able to alter their circadian rhythm in order to improve performance during night shift work, continue day-time interaction with peers and have the ability to sleep at night on days off.
The study appears in the journal Sleep.