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Randomised controlled trial of the efficacy of a blue-enriched light intervention to improve alertness and performance in night shift workers

journal contribution
posted on 15.06.2018, 00:00 by TL Sletten, S Ftouni, CL Nicholas, M Magee, RR Grunstein, Sally FergusonSally Ferguson, DJ Kennaway, D O'Brien, SW Lockley, SMW Rajaratnam
Objectives Night workers often experience high levels of sleepiness due to misalignment of the sleep-wake cycle from the circadian pacemaker, in addition to acute and chronic sleep loss. Exposure to light, in particular short wavelength light, can improve alertness and neurobehavioural performance. This randomised controlled trial examined the efficacy of blue-enriched polychromatic light to improve alertness and neurobehavioural performance in night workers. Design Participants were 71 night shift workers (42 males; 32.8±10.5 years) who worked at least 6 hours between 22:00 and 08:00 hours. Sleep-wake logs and wrist actigraphy were collected for 1-3 weeks, followed by 48-hour urine collection to measure the circadian 6-sulphatoxymelatonin (aMT6s) rhythm. On the night following at least two consecutive night shifts, workers attended a simulated night shift in the laboratory which included subjective and objective assessments of sleepiness and performance. Workers were randomly assigned for exposure to one of two treatment conditions from 23:00 hours to 07:00 hours: blue-enriched white light (17 000 K, 89 lux; n=36) or standard white light (4000 K, 84 lux; n=35). Results Subjective and objective sleepiness increased during the night shift in both light conditions (p < 0.05, η p 2 =0.06-0.31), but no significant effects of light condition were observed. The 17 000 K light, however, did improve subjective sleepiness relative to the 4000 K condition when light exposure coincided with the time of the aMT6s peak (p < 0.05, d=0.41-0.60). Conclusion This study suggests that, while blue-enriched light has potential to improve subjective sleepiness in night shift workers, further research is needed in the selection of light properties to maximise the benefits. Trial registration number The Australian New Zealand Clinical Trials Registry ACTRN12610000097044 (https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=320845 & isReview=true). © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Funding

Category 1 - Australian Competitive Grants (this includes ARC, NHMRC)

History

Volume

74

Issue

11

Start Page

792

End Page

801

Number of Pages

10

eISSN

1470-7926

ISSN

1351-0711

Publisher

B M J Group, UK

Peer Reviewed

Yes

Open Access

No

Acceptance Date

10/05/2017

External Author Affiliations

Harvard Medical School, Boston, Massachusetts, USA; University of Adelaide; Royal Prince Alfred Hospital, Sydney; University of Sydney; The University of Melbourne; CRC for Alertness, Safety and Productivity, Clayton, Victoria; Monash University

Author Research Institute

Appleton Institute

Era Eligible

Yes

Journal

Occupational and Environmental Medicine