Chronic artificial blue-enriched white light is an effective countermeasure to delayed circadian phase and neurobehavioral decrements

PLoS One. 2014 Jul 29;9(7):e102827. doi: 10.1371/journal.pone.0102827. eCollection 2014.


Studies in Polar Base stations, where personnel have no access to sunlight during winter, have reported circadian misalignment, free-running of the sleep-wake rhythm, and sleep problems. Here we tested light as a countermeasure to circadian misalignment in personnel of the Concordia Polar Base station during the polar winter. We hypothesized that entrainment of the circadian pacemaker to a 24-h light-dark schedule would not occur in all crew members (n = 10) exposed to 100-300 lux of standard fluorescent white (SW) light during the daytime, and that chronic non-time restricted daytime exposure to melanopsin-optimized blue-enriched white (BE) light would establish an a stable circadian phase, in participants, together with increased cognitive performance and mood levels. The lighting schedule consisted of an alternation between SW lighting (2 weeks), followed by a BE lighting (2 weeks) for a total of 9 weeks. Rest-activity cycles assessed by actigraphy showed a stable rest-activity pattern under both SW and BE light. No difference was found between light conditions on the intra-daily stability, variability and amplitude of activity, as assessed by non-parametric circadian analysis. As hypothesized, a significant delay of about 30 minutes in the onset of melatonin secretion occurred with SW, but not with BE light. BE light significantly enhanced well being and alertness compared to SW light. We propose that the superior efficacy of blue-enriched white light versus standard white light involves melanopsin-based mechanisms in the activation of the non-visual functions studied, and that their responses do not dampen with time (over 9-weeks). This work could lead to practical applications of light exposure in working environment where background light intensity is chronically low to moderate (polar base stations, power plants, space missions, etc.), and may help design lighting strategies to maintain health, productivity, and personnel safety.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antarctic Regions
  • Circadian Rhythm*
  • Humans
  • Light*
  • Seasons
  • Sleep
  • Sleep Disorders, Circadian Rhythm / etiology

Grants and funding

This work was supported by the European Space Agency (ESA), and a grant from the Centre National d'Études Spatiales (CNES, France) to CG. RPN was funded by “Ministère de l'Enseignement Supérieur et de la Recherche Français” and “Fédération des Aveugles et Handicapés Visuels de France.” Light bulbs were provided by Philips Lighting B.V., Eindhoven, The Netherlands. LightWatcher data loggers and the Neurobehavioral Test Battery were provided by Object-Tracker, Austria. The funder, Wolf Technologieberatung - Object-Tracker, provided support in the form of salaries for authors [LW], but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. All funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.