“Many species (including humans) need darkness to survive and thrive.” — American Medical Association Council on Science and Public Health (2012)
Most species on our planet evolved with day and night cycles. These cycles are linked to our internal biology. We have a circadian rhythm, a “body-clock”, which helps cue our body to get hungry or tired and to release certain hormones.
Many scientific studies have been done on the human circadian rhythm and its importance to our health.
You probably have heard that people should avoid screen time before going to bed. Most devices with screens emit a high color temperature of light, which confuses our brains into thinking it's daytime. This artificial light affects how our bodies produce the hormone melatonin. Melatonin cues our bodies to become sleepy. But melatonin also provides a number of other important bodily functions. It boosts the immune system, lowers cholesterol, has antioxidant properties, and helps the functioning of the thyroid, ovaries, pancreas, testes and adrenal glands.
So what happens to our bodies with the loss of dark skies? Research into this question is ongoing, but so far scientists have learned that excessive exposure to artificial light at night may increase sleeplessness, depression, diabetes, breast cancer, and obesity.
It sounds scary, but there is a lot you can do to reduce your exposure to night time light. If you live in a bright neighborhood, try installing blackout shades. For lights in the house that you want to keep on, look for bulbs that will put out a reddish light. Healthiest color temperatures for nighttime lighting are in the range of 1500-2700 Kelvin.
You can also change your smartphone and computer to automatically put out a lower light at night. The International Dark Sky Association has a list of color temperature apps you can download, and more information on choosing the right light bulb for your family’s health.