According to their findings, exposure to even moderate lighting during sleep may increase the risk of several serious health conditions, including cardiovascular health and insulin resistance.
“The results from this study demonstrate that just a single night of exposure to moderate room lighting during sleep can impair glucose and cardiovascular regulation, which are risk factors for heart disease, diabetes, and metabolic syndrome,” said researcher Dr. Phyllis Zee. “It’s important for people to avoid or minimize the amount of light exposure during sleep.”
Light disruptions may worsen health
The researchers had 20 young adults participate in a sleep experiment that tested out how exposure to different levels of light affected health outcomes. For two consecutive nights, they slept in a room with dim lighting (3 lux). They then slept in a room with brighter overhead lighting (100 lux) for another night. In both instances, the team tracked their sleep quality, melatonin levels, insulin resistance, and cardiovascular health.
The study showed that when the participants slept in the brighter room, it significantly impacted their heart rates. Not only did the participants’ heart rates increase, but the light disruption affected how fast the blood pumped to the heart and the force of the heart pumping.
“We showed your heart rate increases when you sleep in a moderately lit room,” said researcher Dr. Daniela Grimaldi. “Even though you are asleep, your autonomic nervous system is activated. That’s bad. Usually, your heart rate together with other cardiovascular parameters are lower at night and higher during the day.”
The researchers also learned that insulin resistance was higher when the participants slept in the brighter room. When insulin resistance is high, the body can’t use glucose to make energy; over time, this can increase blood sugar, which can also increase the risk for diabetes.
The researchers noted that the participants didn’t report feeling any of these physiological changes throughout the night or the next morning.
“But the brain senses it,” Dr. Grimaldi said. “It acts like the brain of somebody whose sleep is light and fragmented. The sleep physiology is not resting the way it’s supposed to.”
In terms of sleep quality, exposure to any kind of light prevented the participants from ever going into a deep sleep. This light exposure made it more difficult for the participants to enter rapid eye movement (REM) sleep or slow wave sleep, both of which are critical for a healthy sleep cycle.
Keeping the light out at night
Though many consumers may be tempted to sleep with a light on nearby or leave the TV on overnight, the researchers hope these findings encourage them to do otherwise.
The team has very explicit advice for consumers who may have questions about how to set up their sleeping space. “If you’re able to see things really well, it’s probably too light,” Dr. Zee said.