Lately, there's been talk about blue light from smartphones, laptop screens, etc. affecting our sleeping pattern, in addition to the discussion of how people sleep much earlier than the technological age due to the absence of electric lights. That was thought to be a healthier lifestyle.
Blue light is supposed to disrupt the melatonin (sleep hormone) level, thereby not only affecting our circadian rhythm, but other factors of health (antioxidant related to cancer, etc.) as well which the hormone is responsible for.