Circadian rhythms, the body’s internal clock, are important in determining human sleep patterns. Circadian rhythms are physical, mental and behavioral changes that follow a roughly 24 hour cycle that respond to environmental light and darkness. The production of melatonin, the hormone that makes you sleepy, is regulated by circadian rhythms. But what happens when Artificial Light At Night (ALAN) interferes with the body’s natural circadian rhythms?
Whether it’s street lights, outdoor night lights, digital clocks, phones, kindles, or the glare of the television: all can have dire health effects including poor sleep, type 2 diabetes, increased chance of obesity, cancer, and depression. There is emerging evidence that links exposing the retina of the eye at night to light interferes with the body’s circadian rhythms. The human body’s internal clock helps to regulate digestion, immune function, and hormonal release. Dozens of animal cancer studies have shown that animals exposed to light at night develop tumors more readily than those kept in the dark. Additional animal studies have demonstrated increased anxiety and weight gain when they were exposed to light at night.
Although the link between ALAN, melatonin levels, and risk of disease and cancer needs further exploration there is no doubt that 2.5 billion years of life have evolved around the earth’s 24 hour cycle. In the meantime, I’m sleeping in the dark, just in case.
~Ed Deboo, PT
Physical Therapy, Bellingham, WA