Bright-light effects on cognitive performance in elderly persons working simulated night shifts: psychological well-bein
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ORIGINAL ARTICLE
Bright-light effects on cognitive performance in elderly persons working simulated night shifts: psychological well-being as a mediator? Veronika Kretschmer • Klaus-Helmut Schmidt Barbara Griefahn
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Received: 2 April 2012 / Accepted: 16 October 2012 Ó Springer-Verlag Berlin Heidelberg 2012
Abstract Purpose The present study examined whether the relationship between light exposure and cognitive functioning is mediated by psychological well-being in elderly persons working night shifts. The role of psychological well-being has been neglected so far in the relationship between bright light and cognitive performance. Sleepiness and mood were applied as indicators of psychological well-being. Cognitive functioning was examined in terms of concentration, working memory, and divided attention. Methods A total of thirty-two test persons worked in three consecutive simulated night shifts, 16 under bright light (3,000 lux) and 16 under room light (300 lux). Concentration, working memory, and divided attention were measured by computerised tasks. The hypothesised mediators were recorded by questionnaires. Results Mediation analyses were conducted for estimating direct, total, and indirect effects in simple mediation models. Results indicate that sleepiness and mood did not function as mediators in the prediction of concentration, working memory, and/or divided attention by light exposure. Conclusions Sleepiness led to an underestimation of the positive bright-light effect on concentration performance. Mood showed only a random effect due to the positive bright-light effect on working memory. Sleepiness and mood could completely be excluded as mediators in the relationship between light exposure and cognitive
V. Kretschmer (&) K.-H. Schmidt B. Griefahn Leibniz Research Centre for Working Environment and Human Factors at the TU Dortmund, Ardeystr. 67, 44139 Dortmund, Germany e-mail: [email protected]
functioning. This study underlines that psychological wellbeing of elderly persons is not a critical component in the treatment of bright light on cognitive performance in the night shift workplace. In summary, it becomes evident that bright light has a strong direct and independent effect on cognitive performance, particularly on working memory and concentration. Keywords Night work Elderly persons Bright light Cognitive performance Mood Sleepiness
Introduction Since the beginning of industrialisation, there has been a renewed rise in the use of shift work as an instrument of work time organisation in recent years. Currently, about 20 % of the employees in the European Union do shift work (Ku¨mmerling 2007). In traditional shift work research, night work is considered to be a type of working time that causes greatest impairments. A growing body of evidence suggests that night shift work leads to deteriorated cognitive performance during working time (SmithCoggins et al. 1994). Furthermore, for night shifts, a lower cognitive performance has been demonstrated in comparison with other shifts (
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