Sex differences in light sensitivity impact on brightness perception, vigilant attention and sleep in humans

Abstract

Artificial light endows a “round-the-clock”, 24-h/7-d society. Chronic exposure to light at night contributes to health hazards for humans, including disorders of sleep. Yet the influence of inter-individual traits, such as sex-differences, on light sensitivity remains to be established. Here we investigated potential sex-differences to evening light exposure of 40 lx at 6500 K (blue-enriched) or at 2500 K (non-blue-enriched), and their impact on brightness perception, vigilant attention and sleep physiology. In contrast to women, men had higher brightness perception and faster reaction times in a sustained attention task during blue-enriched light than non-blue-enriched. After blue-enriched light exposure, men had significantly higher all-night frontal NREM sleep slow-wave activity (SWA: 2–4 Hz), than women, particularly during the beginning of the sleep episode. Furthermore, brightness perception during blue-enriched light significantly predicted men’s improved sustained attention performance and increased frontal NREM SWA. Our data indicate that, in contrast to women, men show a stronger response to blue-enriched light in the late evening even at very low light levels (40lux), as indexed by increased vigilant attention and sleep EEG hallmarks. Collectively, the data indicate that sex differences in light sensitivity might play a key role for ensuring the success of individually-targeted light interventions.

Melatonin suppression is exquisitely sensitive to light and primarily driven by melanopsin in humans

“…In addition to light conditions, other factors might also change the thresholds of sensitivity, such as gender, age, circadian phase, medical conditions, and light history. 5,11,39,43,44 Our findings have physiological and practical implications. Given that melatonin appears to be exquisitely sensitive to low light levels, melatonin suppression could be engaged as soon as one is exposed to light, even at relatively low intensities.…”

“…Thus, we propose to use cautious interpretation before extrapolating our results to polychromatic lights and light‐emitting devices, and also to other settings such as real‐life conditions. In addition to light conditions, other factors might also change the thresholds of sensitivity, such as gender, age, circadian phase, medical conditions, and light history …”

The impact of a view from a window on thermal comfort, emotion, and cognitive performance

“…Previous studies found that perceptions of the environment and related psychological impacts differ across females and males. This has been found in studies of thermal comfort [76][77][78], visual perception [79,80], and cognitive performance [81,82]. Order effect has also been a potential moderating factor in similar experimental designs [27,61].…”

Can night shift workers benefit from light exposure?

“…; Chellappa et al . ). Sex differences in light sensitivity might play a key role for individual shift work interventions.…”

“…As the authors point out, there is an 'apparent sex difference' as none of the six males included in the analysis advanced their circadian phase. Recently, two studies examining light sensitivity, circadian regulation and cognitive performance have shown sex differences (Santhi et al 2016;Chellappa et al 2017). Sex differences in light sensitivity might play a key role for individual shift work interventions.…”