New studies reveal that exposure to even dim light during sleep can have adverse effects on the body, potentially causing cardiovascular and metabolic health defects, according to NPR.

Even a small amount of light can get through the eyes and affect the brain during sleep, Dr. Phyllis Zee, the senior author of one study on the subject, told NPR.

What are the effects? Several researchers have discovered that exposure to low amounts of light during sleep can suppress melatonin levels and cause people to be in a more active and alert state.

  • “Studies show artificial light at night can suppress melatonin levels, and scientists have found a link between the disruption of melatonin and several diseases, including cancer and diabetes,” reported NPR.
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  • “In healthy adults, one night of moderate light exposure during sleep increases nighttime heart rate, decreases heart rate variability (higher sympathovagal balance), and increases next-morning insulin resistance when compared to sleep in a dimly lit environment,” according to a sleep study published by the Proceedings of the National Academy of Sciences.
  • Researchers report that even small amounts of light at night can activate the part of the nervous system associated with fight or flight, according to NPR.
  • “The changes in cardiovascular function suggest the small amount of light was enough to shift the nervous system to a more activated and alert state,” according to NPR’s coverage on the studies.

Screen time and sleep: A study published in Chronobiology International reported that routine exposure to artificial light at night in work, including light from phones and computers, is linked with an increased risk of breast and prostate cancer.

  • Data has also revealed that for women, sleeping with a TV or light on was associated with a 14% increased risk of gaining 11 pounds over the course of five years, a study in JAMA Internal Medicine states.