Randomized trial of polychromatic blue-enriched light for circadian phase shifting, melatonin suppression, and alerting responses

Blue-Enriched White Light Improves Performance but Not Subjective Alertness and Circadian Adaptation During Three Consecutive Simulated Night Shifts

“…Subjective sleepiness was reduced with 17,000 K light compared to standard light, but 17,000 K light did not affect PVT measured RTs or lapses during light exposure (Hanifin et al, 2019). Hanifin et al (2019) applied lower illuminance and a different spectral distribution compared to the present study. However, in the study by Hanifin et al (2019) the melanopic illuminance in the standard (79 lx) light was only slightly lower than in the 2500 K (86 lx) light used in the present study, while the 17,000 K (133 lx) light in Hanifin et al (2019) had lower melanopic illumination than the 7000 K (192 lx) light in the present study.…”

“…Thus, it is a little surprising that we did not find stronger effects of 7000 K light on subjective alertness/sleepiness, as the mechanism is thought to be mediated by melanopsin expressing ipRGCs projecting to brain areas important for alertness and arousal regulation (Vandewalle et al, 2009;Warthen and Provencio, 2012). Still, compared to our study, much more rigorous control of participants' exposure was taken, e.g., an ophthalmologic head holder was used to maintain a fixed head position and gaze, and light history was controlled with dim light and blindfolds prior to light exposure (Hanifin et al, 2019). As we found beneficial effects of 7000 K compared to 2500 K light on PVT measures, it is somewhat surprising that no effects were found during blue-enriched light exposure in the more controlled study by Hanifin et al (2019).…”

“…Hanifin et al (2019) applied lower illuminance and a different spectral distribution compared to the present study. However, in the study by Hanifin et al (2019) the melanopic illuminance in the standard (79 lx) light was only slightly lower than in the 2500 K (86 lx) light used in the present study, while the 17,000 K (133 lx) light in Hanifin et al (2019) had lower melanopic illumination than the 7000 K (192 lx) light in the present study. Thus, it is a little surprising that we did not find stronger effects of 7000 K light on subjective alertness/sleepiness, as the mechanism is thought to be mediated by melanopsin expressing ipRGCs projecting to brain areas important for alertness and arousal regulation (Vandewalle et al, 2009;Warthen and Provencio, 2012).…”

Dissecting the Response to Blue Light

“…In addition to wavelength (more or less blue), light's suppressive effect on melatonin also depends on three other factors: timing, duration, and intensity. That said, the science is clear on the fact that—timing, duration, and intensity being equal—a blue‐light wavelength will have a much greater suppressive force on melatonin than light with low or no blue light 2 …”

Students in Good Mood Appear Slower and Less Accurate: A Pilot Study Investigating Dynamic Lighting Impact on Students’ Perception and Performance

“…The ipRGC-influenced light effects are not only affecting the circadian processes in the human body but acutely enhance alertness and cognitive performance as well. Exposure to high light levels, especially with a high short wavelength content, can increase alertness (e.g., Lockley et al, 2006, Vandewalle et al, 2009, Keis et al, 2014, Cajochen et al, 2019, Hanifin et al, 2019 where efficiency of an exposure of just 18 minutes has already been shown (Vandewalle et al, 2007).…”