How the Lighting Revolution Has Affected the Way We Sleep
For many centuries, humans relied on candlelight at night. Then came the development of incandescent bulbs. These light sources emit “warmer” light (reddish in color), which is conducive for illuminating the space at night around you without affecting your sleep.
Today, we not only have new advances in lighting technology (thanks to fluorescent and LED bulbs), we also have greater exposure to it. In fact, many people — labeled as the “Indoor Generation” — spend as much as 90% of their time indoors under artificial lighting and/or using digital devices with LED screens. These light sources emit “cooler” light (bluer in color) that mimic daylight, when the sun is at its highest point in the sky. Given that blue light promotes alertness, exposure to blue wavelengths at night is not ideal.
See the chart below which shows the spectrums of different light sources: