Monochromatic light exposure: effects on daytime sleepiness

During diurnal Circadian phase,“Red”light (630 nm) administrationis associated with greater alerting effects when compared to“Blue”light (470 nm). Conversely, short wavelength light has been found toaffect Circadian output exerting non-visual responses in suppressingmelatonin; thus reducing sleepiness and increasing performance ofcognitive tasks during the night. Throughout exposure to differentlight spectra by means of a LED light box, we aimed to disentangle arole for sleep Homeostatic pressure to modulate alerting effects ofmonochromatic light administration during postprandial hours. Elevenparticipants (6 Males) were exposed alternatively to 45 minutes ofboth light Conditions (Blue/Red). Baseline (BL - 10.00 am), Pre-Light(L1 - 2.00 pm) and Post-Light (L2 - 3.00 pm). Objective sleepinesswas assessed by Psychomotor Vigilance Task (PVT); in additionVisual Analogue Scale (VAS) was administered in order to assesssubjective Vigilance. Two separate 293 mixed-model ANOVAsshowed a significant time effect on both objective (F(2,40)=8.2963;P=0.00097) and subjective measures (F(2,40)=6.410;P=0.00385) with participants showing increased sleepiness. A significantinteraction effect was found only for PVT (F(2,40)=3.4611 ;P=0.04108); Post-hoc comparison found that daytime sleepinesswas reduced only on Post-Light exposure in the Blue condition. Giventhese preliminary results, it is possible to hypothesize a wavelengthsensibility also for homeostatic drive.