TY - JOUR T1 - Blue-enriched office light competes with natural light as a zeitgeber JO - Scandinavian Journal of Work, Environment & Health PY - 2011/9VL - 37 IS - 5 SP - 437 EP - 445 AU - Vetter, Céline AU - Juda, Myriam AU - Lang, Dieter AU - Wojtysiak, Andreas AU - Roenneberg, Till M3 - doi: 10.5271/sjweh.3144 UR - https://www.sjweh.fi/show_abstract.php?abstract_id=3144 KW - blue-enriched office light KW - chronotype KW - circadian clock KW - field study KW - light environment KW - light power spectrum KW - natural light KW - office worker KW - sleep–wake cycle KW - zeitgeber N2 - '

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OBJECTIVES ': 'Circadian regulation of human physiology and behavior (eg, body temperature or sleep-timing), depends on the “zeitgeber” light that synchronizes them to the 24-hour day. This study investigated the effect of changing light temperature at the workplace from 4000 Kelvin (K) to 8000 K on sleep−wake and activity−rest behavior.

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METHODS ': 'An experimental group (N=27) that experienced the light change was compared with a non-intervention group (N=27) that remained in the 4000 K environment throughout the 5-week study period (14 January to 17 February). Sleep logs and actimetry continuously assessed sleep−wake behavior and activity patterns.

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RESULTS ': 'Over the study period, the timing of sleep and activity on free days steadily advanced parallel to the seasonal progression of sunrise in the non-intervention group. In contrast, the temporal pattern of sleep and activity in the experimental group remained associated with the constant onset of work.

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CONCLUSION ': 'The results suggest that artificial blue-enriched light competes with natural light as a zeitgeber. While subjects working under the warmer light (4000 K) appear to entrain (or synchronize) to natural dawn, the subjects who were exposed to blue-enriched (8000 K) light appear to entrain to office hours. The results confirm that light is the dominant zeitgeber for the human clock and that its efficacy depends on spectral composition. The results also indicate that blue-enriched artificial light is a potent zeitgeber that has to be used with diligence.

SN - 0355-3140 ER -