BLUE LIGHT Exposure Reduces Objective Measures of Sleepiness during Prolonged Nighttime Performance Testing

Abstract

This study examined the effects of nocturnal exposure to dim, narrowband blue light (460 nm, ∼1 lux, 2 µW/cm²), compared to dim broad spectrum (white) ambient light (∼0.2 lux, 0.5 µW/cm²), on subjective and objective indices of sleepiness during prolonged nighttime performance testing. Participants were also exposed to a red light (640 nm, ∼1 lux, 0.7µW/cm²) placebo condition. Outcome measures were driving simulator and psychomotor vigilance task (PVT) performance, subjective sleepiness, salivary melatonin, and electroencephalographic (EEG) activity. The study had a repeated-measures design, with three counterbalanced light conditions and a four-week washout period between each condition. Participants (n = 8) maintained a regular sleep-wake schedule for 14 days prior to the ∼14 h laboratory study, which consisted of habituation to light conditions followed by neurobehavioral performance testing from 21:00 to 08:30 h under modified constant-routine conditions. A neurobehavioral test battery (2.5 h) was presented four times between 21:00 and 08:30 h, with a 30 min break between each. From 23:30 to 05:30 h, participants were exposed to blue or red light, or remained in ambient conditions. Compared to ambient light exposure, blue light exposure suppressed EEG slow wave delta (1.0–4.5 Hz) and theta (4.5–8 Hz) activity and reduced the incidence of slow eye movements. PVT reaction times were significantly faster in the blue light condition, but driving simulator measures, subjective sleepiness, and salivary melatonin levels were not significantly affected by blue light. Red light exposure, as compared to ambient light exposure, reduced the incidence of slow eye movements. The results demonstrate that low-intensity, blue light exposure can promote alertness, as measured by some of the objective indices used in this study, during prolonged nighttime performance testing. Low intensity, blue light exposure has the potential to be applied to situations where it is desirable to increase alertness but not practical or appropriate to use bright light, such as certain occupational settings.

• Blue light
• Driving simulator
• Melatonin
• Sleep deprivation
• Performance
• Electroencephalogram

Acknowledgments

We acknowledge David Kennaway and Athena Voultsios in the Department of Obstetrics and Gynaecology, University of Adelaide for the melatonin radioimmunoassays, and Simon Moss for statistical advice. We also thank Derk-Jan Dijk for his advice on the protocol design, Steven Lockley for his constructive comments on the manuscript, and Russell Conduit, Christopher Hocking, Joshua Wood, Claire Swann, and Timothy Friedman for their assistance with data collection.

This research was supported in part by research grants from Philips Lighting, Monash University, and National Health and Medical Research Council (#436758).