Virtually all light can affect sleep, but not all types of light have the same impact. Daylight, which in direct sunlight has up to 10,000 lux, a unit to measure illuminance7, is far more intense than even bright office lighting, which rarely reaches about 500 lux. For this reason, daylight is a profound influence on sleep and circadian timing.
There can be important differences between types of artificial light as well. Some types have more illuminance and brightness. That said, even light that appears to have the same brightness may, in reality, have a different wavelength, changing how it’s perceived by the eye and brain.
For example, blue light has a short wavelength and is emitted by many LEDs. Studies have found that it has a significantly larger effect on melatonin and circadian rhythm8 than light with a longer wavelength. Many electronic devices, including cell phones, tablets, and laptops, emit blue light, and their extensive evening use can contribute to sleep problems9.
7. Blume, C., Garbazza, C., & Spitschan, M. (2019). Effects of light on human circadian rhythms, sleep and mood. Somnologie : Schlafforschung und Schlafmedizin = Somnology : sleep research and sleep medicine, 23(3), 147–156.
8. Lockley, S. W., Brainard, G. C., & Czeisler, C. A. (2003). High sensitivity of the human circadian melatonin rhythm to resetting by short wavelength light. The Journal of clinical endocrinology and metabolism, 88(9), 4502–4505.
9. Carter, B., Rees, P., Hale, L., Bhattacharjee, D., & Paradkar, M. S. (2016). Association Between Portable Screen-Based Media Device Access or Use and Sleep Outcomes: A Systematic Review and Meta-analysis. JAMA pediatrics, 170(12), 1202–1208.
Article Source: https://www.sleepfoundation.org/bedroom-environment/light-and-sleep#references-78846