Ergonomics: Melatonin rhythm

Quite often, the lighting conditions in artificially illuminated windowless workplaces do not meet the ergonomical standards. In this context, low lighting intensities not only debilitate the employees vision but irritate the non-visual aspects of light as well, i.e. they impair the subject’s regular circadian rhythm of melatonin and other parameters. An insufficient suppression of daytime melatonin synthesis extends its sphere of action. The biological effects of melatonin include the timing of core body temperature, the setup of diurnal cortisol rhythms, and the promotion of sleep (Arendt and Skene, 2005; Lewy et al., 1992; Zhdanova, 2005).

Thus, one ergonomical concern in the strategy of workplace illuminationshould be to allow for an adjustment of a regular daytime melatonin rhythm. This will help to avoid the risks of on-the-job sleepiness, decreased alertness, and reduced job performance. In our study, highest aMT6-s concentrations could be detected in urine samples collected at the beginning of the experimental office work at 09:00 a.m. In the course of the day, there was a significant drop in aMT6-s levels with lowest values at 05:00 p.m. This is in congruence with the circadian profile reported for melatonin in the literature and is regarded to be due to bright light exposure (Lewy et al., 1980; Lynch et al., 1975).

Effects of variable lighting intensities and colour temperatures on sulphatoxymelatonin and subjective mood in an experimental office workplace, Applied Ergonomics Journal, Nov 2007, Elsevier Publishing

"In the bluish light scenario, a significant improvement in restless behaviour was observed in the intervention group, as well as a significant increase in the range of tympanic temperature. These effects were not found in the yellowish light scenario. Further evidence is found that high-intensity bluish light may play a role in managing restless behaviour and improving circadian rhythmicity in institutionalised older adults with dementia."

Ambient bright light in dementia: Effects on behaviour and circadian rhythmicity , Building and Environment, Vol 44, 2008


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