Sleeping for just one night with dim light, such as a TV set with the sound off, raised blood sugar and heart rate in healthy young people who participated in a sleep lab experiment, a new study finds.
The dim light penetrated through the eyelids and disrupted sleep despite the fact that participants slept with their eyes closed, said study author Phyllis Zee, director of the Center for Circadian Medicine and Sleep at Northwestern University’s Feinberg School of Medicine. .
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 early death.
Elevated 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 it eventually loses its 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, disruptions 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 this explain why there is a higher prevalence of diabetes or obesity (in society)?” asked Zee.
Zee and his team selected 20 healthy people in their 20s and had them spend two nights in a sleep lab. The first night was spent in a pitch-dark 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 series of objective measures of sleep quality. So that the data could be collected with minimal interference, they slept with an intravenous needle connected to long tubes that wind through the room and pass through a hole that reaches the researcher’s laboratory. Blood was collected without ever touching the sleeping participants.
“We recorded the brain waves and were able to tell what stage of sleep the person was in,” Zee said. “We recorded their breathing, heart rate, electrocardiogram and also drew blood from them to measure melatonin levels while they slept.” Melatonin is a hormone that regulates the body’s circadian rhythm, or the biological clock of 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 a brightness equivalent to “a very, very dark, cloudy day or street lights.” coming in 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 that small amount of light created a deficit of slow waves and rapid eye movement while they slept, the stages of sleep where most cell turnover occurs, Zee said.
In addition, 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.
The light wasn’t strong enough, however, 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 clearly should pay attention to the light in your room,” she said. “Make sure you start dimming the lights at least an hour or two before going to bed to prepare your sleeping environment.”
Check your room for unnecessary light sources, he added. If a night light is needed, keep it dim and at floor level, “so it’s more reflected than near eye or bed level,” she suggested.
Also be mindful of the type of light you have in your room, she added, and cut out any light in the blue spectrum, such as those emitted by electronic devices such as televisions, cell phones, tablets, and computers or laptops.
“Blue light is the most stimulating type of light,” Zee said. “If you have to have a light on for safety reasons, change the color of it. You want to choose lights that have more reddish or brownish tones.”
LED lights can be purchased in any color, including shades of red and brown.
Source: CNN Brasil
