Nie and colleagues evaluated lighting’s influence on sleep quality and cognitive performance; participants in their study were 18 to 25 years old. The researchers reported that they “optimized and fabricated a four-channel mixed white light with peak wavelengths of 429, 523, 591, and 621 nm. Comparing with common white light emitting diode (LED) (5798 K, 212.7 lx), the mixed white light has lower correlated color temperature (CCT) (2799 K), higher illuminance (356.2 lx), similar melanopic illuminance, and better color fidelity. . . . the mixed white light with higher illuminance . . . results in more melatonin for subjects. More melatonin before sleep benefits the sleep quality by decreasing arousal times and improving sleep continuity. The higher illuminance light environment also promotes the inhibition ability and working memory. Moreover, it presents better color discrimination and less visual fatigue. Therefore, the lower CCT with higher illuminance nocturnal light environment effectively promotes both cognitive performances in the evening and the following sleep quality.”
Jingxin Nie and 18 others. “The Lower Correlated Color Temperature with Higher Illuminance Nocturnal Light Environment Improves Cognitive Performance and Sleep Quality.” Building and Environment, vol. 251, 111221, https://doi.org/10.1016/j.buildenv.2024.111221