Investigating the contribution of short wavelengths in the alerting effect of bright light

Type de document

Études primaires

Année de publication

2015

Langue

Anglais

Titre de la revue

Physiology and Behavior

Première page

81

Dernière page

87

Résumé

Introduction:Short-wavelengths can have an acute impact on alertness, which is allegedly due to their action on intrinsically photosensitive retinal ganglion cells. Classical photoreceptors cannot, however, be excluded at this point in time as contributors to the alerting effect of light. The objective of this study was to compare the alerting effect at night of a white LED light source while wearing blue-blockers or not, in order to establish the contribution of short-wavelengths.

Materials and Methods: 20 participants stayed awake under dim light (<5lx) from 23:00h to 04:00h on two consecutive nights. On the second night, participants were randomly assigned to one light condition for 30min starting at 3:00h. Group A (5M/5F) was exposed to 500μW/cm2 of unfiltered LED light, while group B (4M/6F) was required to wear blue-blocking glasses, while exposed to 1500μW/cm2 from the same light device in order to achieve 500μW/cm2 at eye level (as measured behind the glasses). Subjective alertness, energy, mood and anxiety were assessed for both nights at 23:30h, 01:30h and 03:30h using a visual analog scale (VAS). Subjective sleepiness was assessed with the Stanford Sleepiness Scale (SSS). Subjects also performed the Conners' Continuous Performance Test II (CPT-II) in order to assess objective alertness. Mixed model analysis was used to compare VAS, SSS and CPT-II parameters.

Results: No difference between group A and group B was observed for subjective alertness, energy, mood, anxiety and sleepiness, as well as CPT-II parameters. Subjective alertness (. p<. 0.001), energy (. p<. 0.001) and sleepiness (. p<. 0.05) were, however improved after light exposure on the second night independently of the light condition.

Conclusions: The current study shows that when sleepiness is high, the alerting effect of light can still be triggered at night in the absence of short-wavelengths with a 30minute light pulse of 500μW/cm2. This suggests that the underlying mechanism by which a brief polychromatic light exposure improves alertness is not solely due to short-wavelengths through intrinsically photosensitive retinal ganglion cells. © 2015.

Mots-clés

Sensibilité à la lumière, Light sensitivity, Vigilance

Numéro de projet IRSST

n/a

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