We hear a lot about the effects of light on sleep. Light in the evening—especially the blue light emitted by devices with screens—blocks secretion of the hormone melatonin, causing symptoms of insomnia. Low lighting during the day also delays melatonin onset and shortens the night.
Shift work, in which workers are routinely are exposed to light at night and must sleep during daylight hours, is so likely to disturb people’s sleep that the problem has its own name: Shift Work Sleep Disorder.
Not only do unnatural lighting conditions interfere with sleep. More and more evidence suggests that artificial lighting is behind the uptick in modern diseases such as cancer.