Underexposure to light at work and its association to insomnia and sleepiness. A cross-sectional study of 13296 workers of one transportation company

Damien Leger, Virginie Bayon, Maxime Elbaz, Pierre Philip, Dominique Choudat
Journal of Psychosomatic Research. 2011-01-01; 70(1): 29-36
DOI: 10.1016/j.jpsychores.2010.09.006

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1. J Psychosom Res. 2011 Jan;70(1):29-36. doi: 10.1016/j.jpsychores.2010.09.006.

Underexposure to light at work and its association to insomnia and sleepiness: a
cross-sectional study of 13,296 workers of one transportation company.

Leger D(1), Bayon V, Elbaz M, Philip P, Choudat D.

Author information:
(1)Université Paris Descartes, APHP, Hôtel Dieu, Centre du Sommeil et de la
Vigilance, Paris, France.

BACKGROUND: Light is a powerful synchronizer of the biological clock and of the
sleep/wake cycle. Blind people have more sleep disturbances than people without
eyesight problems. However, whether visually able people who are underexposed to
bright natural light suffer from sleep wake disorders has never been examined.
This study tried to assess the prevalence of sleep and wake disorders in subjects
working in environments that are not exposed to natural light.
METHODOLOGY: A setting-controlled cross-sectional epidemiological study was
carried out. A representative sample of 13,296 French employees of a single
transportation company participated in the study. During working hours, 4635
subjects (34.9%) experienced no light exposure (NLE) and 8661 were partially or
completely exposed (LE) to natural light. Sleep disorders, sleep quality, and
sleepiness were assessed using subjective tools: the Sleep Disorders
Questionnaire-French version (SDQFV) and the Epworth Sleepiness Scale (ESS).
Light exposure was estimated on workers’ schedules and by objective measurements
of light intensity (lux meter).
PRINCIPAL FINDINGS: On a univariate analysis, complaints of poor sleep and
sleepiness were significantly higher in NLE workers compared to LE:
nonrestorative sleep (36.8% vs. 29.5%; P

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