Sleeping just one night with dim lights, such as a TV with the sound off, increased blood sugar and heart rate in healthy young people who took part in a sleep lab experiment, a new study has found.
The dim light penetrated through the eyelids and disrupted sleep despite participants sleeping with their eyes closed, said study author Phyllis Zee, director of the Center for Circadian Medicine and Sleep at the Feinberg School of Medicine in Northwestern University.
Heart rate often drops at night, slowing down as the brain is busy repairing and rejuvenating the body. An elevated heart rate at night has been shown in several studies to be a risk factor for future heart disease and premature death.
High blood sugar levels are a sign of insulin resistance, where the body stops using glucose properly and the pancreas goes into overdrive, flooding the body with extra insulin to compensate until he eventually loses his ability to do so. Over time, insulin resistance can lead to type 2 diabetes.
sleep with eyes closed
Previous research has shown an association between artificial light at night and weight gain and obesity, disturbances in metabolic function, insulin secretion, and the development of diabetes and cardiovascular risk factors.
“Why would sleeping with the lights on affect your metabolism? Could that explain why there is a higher prevalence of diabetes or obesity (in society)?” Zee asked.
Zee and his team selected 20 healthy people in their twenties and had them spend two nights in a sleep lab. The first night was in a darkened room where “you wouldn’t be able to see much, if anything, when your eyes were open,” Zee said.
All study participants were connected to devices that monitor a range of objective measures of sleep quality. So that data could be collected with minimal interference, they slept with an intravenous needle attached to long tubes that wind through the room and pass through a hole that reaches the researcher’s lab. Blood was collected without ever touching the sleeping participants.
“We recorded the brain waves and could tell what stage of sleep the person was in,” Zee said. “We recorded their breathing, heart rate, electrocardiogram and also took blood from them to measure melatonin levels while they slept.” Melatonin is a hormone that regulates the body’s circadian rhythm, or biological clock for sleep and wakefulness.
A random part of the group repeated the same light level for a second night in the lab, while the other part of the group slept with a dim ceiling light, with brightness equivalent to “a very, very dark, cloudy or streetlights.” entering through a window,” Zee said.
“Now these people were sleeping with their eyelids closed,” she explained. “In the literature, the estimate is that about 5% to 10% of the light in the environment would actually pass through the closed eyelid into the eye, so that’s not a lot of light.”
However, even this small amount of light created a deficit of slow waves and rapid eye movements during their sleep, the stages of sleep where most cell turnover occurs, Zee said.
Additionally, heart rate was higher, insulin resistance increased, and the sympathetic (fight or flight) and parasympathetic (rest and relaxation) nervous systems were out of balance, which has been linked to higher blood pressure in healthy people.
However, the light was not strong enough to lower melatonin levels in the body, Zee added. The study was published Monday (14) in the journal Proceedings of the National Academy of Sciences.
What to do?
What advice would Zee give people based on his study and existing research in the field? Close blinds and curtains, turn off all lights, and consider wearing a sleep mask.
“I think the strength of the evidence is that you should definitely be careful with the light in your bedroom,” she said. “Be sure to start dimming the lights at least an hour or two before you go to bed to prepare your sleeping environment.”
Check your bedroom for unnecessary light sources, he added. If a nightlight is needed, keep it low and level with the floor, “so it’s more reflective than near eye level or the bed,” she suggested.
Also be aware of the type of light you have in your bedroom, she added, and cut out any light in the blue spectrum, such as those emitted by electronic devices such as TVs, cell phones, tablets and computers. computers or laptops.
“Blue light is the most stimulating type of light,” Zee said. “If you need to turn on a light for safety reasons, change the color of it. You want to choose more reddish or brownish lights.”
LED lights can be purchased in any color, including shades of red and brown.
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