Long exposure to artificial light at night can affect the body’s ability to produce melatonin, which helps to regulate sleep. It can also weaken the immune system and disrupt hormone production. In addition to the detrimental effects it has on our bodies, routinely staying up late also increases the amount of energy our homes use.
So, unless you work the night short, try to maintain reasonable sleep patterns. You will find yourself feeling better and conserve energy at the same time.
-Abrams, “365 Ways To Save The Earth”, 2008