Do workplace naps increase alertness?
A recent study has found that while scheduled nap breaks for night shift workers can improve alertness and safety when they're most likely to be fatigued, it has mixed results for melatonin regulation.
From monitoring workers in simulated 12-hour night shifts, researchers from Japan's Hokkaido University, National Institute of Occupational Safety and Health and other institutions found those provided with a two-hour nap break showed enhanced alertness and vigilance later in the shift. They hypothesise that being in a dark nap room allows workers to recover from light-induced melatonin suppression.
This suppression, combined with chronic circadian misalignment, has been linked to health problems like cardiovascular disease, diabetes, obesity, depression and cancer among shift workers.
However, they found the increased melatonin concentration in workers who took nap breaks "rapidly diminished" after they went back to work, and at the end of the simulated shifts, there was no significant difference in melatonin levels between workers who did and did not have a nap.
The findings show a nap break strategy can enhance workers' alertness during the late parts of night shifts and reduce fatigue-related safety risks, but is unlikely to mitigate melatonin suppression.
"The most effective way to prevent melatonin suppression during night work may therefore be to reduce the intensity of light and short-wavelength light as much as possible," they said, "However, bright and or blue-enriched lighting is desirable for providing night workers with good visibility and alertness."
Taking a nap during a night shift is widely believed to "relieve sleep pressure and recover alertness and performance losses", the researchers say, noting that most shift workers try to have afternoon or evening naps before night work to mitigate fatigue and reduced alertness, but it is often difficult to fall asleep at those times.
Read more: Sang-il Lee, et al Effects of 2-hour night time nap on melatonin concentration and alertness during 12-hour simulated night work, [Abstract] Industrial Health, published online September 2021, doi: 10.2486/indhealth.2020-0245. Source: OHSAlert