When the lights went out in Los Angeles after an earthquake in 1994, people called emergency centers to report a strange, giant, silvery cloud overhead. It was something they’d never seen before, something many humans alive today have not seen: the Milky Way, a swath of stars toward the center of our galaxy which, under totally dark skies in remote areas, graces the heavens like a river of silk. Without the bright lights of the city, many people experienced the natural phenomena for the first time.
Light pollution, or “loss of night,” as it is sometimes called, has only gotten worse since then, rendering all but a handful of stars invisible from big cities. But the effects go beyond frustrating backyard astronomers. Growing research suggests that bright outdoor lighting negatively affects sleep and moods in people young and old, and may even increase the risk of disease.
In places across America where artificial outdoor light is brightest at night, teenagers sleep on average 11 minutes less than teens in darker areas, according to a new study, published July 8 in the journal JAMA Psychiatry.
Researchers used satellite data to gauge light levels by census blocks (there are more than 200,000 of them in the United States) and compared that to answers from questionnaires given to 10,123 teens, ages 13 to 18. Teens in the brightest areas went to bed late and slept less, even after researchers accounted for population density. They were also more likely to have anxiety or mood disorders, including meeting the diagnostic criteria for bipolar disorder.
In places across America where artificial outdoor light is brightest at night, teenagers sleep on average 11 minutes less than teens in darker areas.
The study doesn’t prove that light is the only factor disrupting sleep. Light could be indicative of other issues, including noise.
“Although environmental light exposure is only one factor in a more complex network of influences on sleep and behavior, it is likely to be an…