Study shows how shift workers can improve job performance and implement a realistic sleep schedule

Dec 01, 2008

A study in the Dec. 1 issue of the journal Sleep shows that the 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.

Results show that performance was better for the experimental subjects than the controls. When the phase delays of the experimental group had likely reached the compromise circadian position, performance for this 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 major finding of this study was that complete physiological adaptation to a night shift and day sleep schedule does not appear necessary in order to improve night shift alertness and lengthen daytime sleep," said lead author Mark Smith, post-doctoral fellow in the Biological Rhythms Research Laboratory at Rush University Medical Center in Chicago. "Instead, we found that partial physiological adaptation using scheduled exposure to light and darkness is sufficient to bring night shift performance back to daytime levels. "

This study, which was number three in a series of five conducted between May and October 2007, was to establish a compromise phase position for permanent night shift work, in which the circadian clock is delayed to only partially align with the day sleep period. This partial entrainment could reduce the performance and alertness decrements during night shifts and allow a sleep schedule that is compatible with both night shifts and days off.

"Despite the effectiveness of complete adjustment to a night shift schedule for improving nighttime alertness and lengthening daytime sleep, we think that most real shift workers want to be awake on their days off, and so would be unwilling to adopt such a schedule because of the social constraints that are associated with it," said Smith.

Twenty-four healthy subjects were included in the study 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.

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. Control subjects remained in normal room light during night shifts, wore lightly tinted sunglasses when outside, and had unrestricted sleep and outdoor light exposure. Measurements of performance were assessed with the Automated Neurophysioloical Assessment Metrics (ANAM) test battery on desktop computers. The ANAM battery included simple reaction time, procedural memory, code substitution, mathematical processing and matching simple tasks.

Subjects in the experimental group achieved a dim light melatonin onset (DLMO) time of 4:30 a.m., which was close to the target compromise phase position and significantly later than the control group's DLMO time of 12:30 a.m. The body temperature minimum (Tmin), an estimate for the sleepiest circadian time, occurs about seven hours after the DLMO. The goal was to delay the sleepiest circadian time so that it fell within the sleep episodes after night shifts and on days off, but to keep it from delaying too far beyond the scheduled sleep episodes on days off.

The data suggest 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.

Source: American Academy of Sleep Medicine

Explore further: Combination of diabetes and heart disease substantially reduces life expectancy

Related Stories

Access to electricity is linked to reduced sleep

Jun 19, 2015

Blame smartphone alerts, constant connectivity and a deluge of media for our society's sleep deprivation. But the root cause of why we get less sleep now than our ancestors did could come down to a much simpler ...

Robotically discovering Earth's nearest neighbors

Apr 28, 2015

A team of astronomers using ground-based telescopes in Hawaii, California, and Arizona recently discovered a planetary system orbiting a nearby star that is only 54 light-years away. All three planets orbit ...

Jab-free snore reminder is gently delivered via pillow

Feb 07, 2014

(Phys.org) —Those sleep partners who are irritated enough to jab and those snoring victims who are startled out of sleep by those jabs all know there has to be a more humane way of curbing the noise. Could ...

Odd work schedules pose risk to health

Apr 17, 2011

(AP) -- Reports of sleeping air traffic controllers highlight a long-known and often ignored hazard: Workers on night shifts can have trouble concentrating and even staying awake.

Recommended for you

WHO says too few countries taxing tobacco products enough

5 hours ago

Taxing cigarettes up to 75 percent of their retail price is among the most effective ways to reduce tobacco use, but too few governments levy high enough taxes, according to a World Health Organization global report released ...

Can four fish oil pills a day keep the doctor away?

6 hours ago

Fish oil is one of the most popular dietary supplements in the U.S. because of the perceived cardiovascular benefits of the omega-3 it contains. However, scientific findings on its effectiveness have been conflicting. New ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.