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  • A study published in Proceedings of the National Academy of Sciences finds that sleeping in a dimly lit room can result in higher heart rates and insulin levels.
  • Participants slept in a dark room one night then split into two groups for the second night, one which returned to the dark room while the other slept in a room with dim lighting.
  • The participants’ sleep quality was measured using a variety of devices, which tracked heart rate, hormone levels, and brain waves.

A new study referenced in Smithsonian Magazine claims that sleeping with a dim light on, such as a nightstand or television screen, can result in higher heart rates and blood sugar levels.

The study, which was published in Proceedings of the National Academy of Sciences, involved 20 participants aged 19 to 36 to spend two nights in a lab under observation by a team of scientists. All of the participants slept in a very dark room on the first night, but the second night saw half of the group sleeping in a dimly lit room while the other half returned to the dark room. The dimly lit room contained a small light that emitted 100 lux, which is a glow reminiscent of streetlights through a window or a television screen at night.

Throughout the study, each participant was connected to devices that measured sleep quality factors such as heart rate, hormone levels, and brain waves. When the participants awoke in the morning, their glucose and insulin levels were measured.

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The study revealed that participants who slept in the dimly lit room spent less time in the restorative stages of deep sleep, going on to experience higher average heart rates and 25% higher insulin levels in the morning.

The science behind the study suggests that light interferes with the body’s functions, as the individuals who slept in the dark room both nights had little difference in their blood sugar control. The scientists suggest covering or blocking all light in the room, and to use a sleeping mask if necessary.