Photos by Klaus Vedfelt / Getty
Turning on the lights and replacing the curtains isn’t a new bed cleaning issue, but this common advice is gaining scientific confidence.
Many Americans sleep in a room that is fitted with some kind of natural light – whether it comes from a TV, an electrical outlet or a street light.
New research shows that getting a night’s sleep with too little light has adverse effects on cardiovascular and metabolic health.
“I’m surprised when I say this, the amount of light that just travels through the eyes to the brain has such a serious impact,” said Drs. Phyllis Zee, lead author of the new research and director of the Center for Circadian and Sleep Medicine at Northwestern University.
The findings of a wide range of evidence suggest that exposure to light at night may be harmful in various ways and can predispose people to certain diseases. mau.
Physiological effects of lung
The small, 20-person study led by Zee and his team at Northwestern was designed to measure the physiological effects of 100 lux of artificial light on healthy cats during their sleep.
“This is about having enough light so you can see your way around, but not enough light to read comfortably,” Zee said. To learn, everyone spent their first night sleeping in a very dark room. The next night, half of them slept in a well -lit room (the light was on).
Now, researchers have run experiments on sleepers: they record their brains, measure their heart rate and draw their blood pressure every hour, and so on. In the morning, they give the two teams a lot of sugar to see how well their system responds to the spike.
The results, published in the Proceedings of the National Academy of Science this month, show the differences between the two groups.
Unlike those who stayed two nights in the dark, the group that was seen in the light had a high heart rate at night. They also increased their insulin levels in the morning, which meant they had more difficulty getting their blood pressure back to normal.
The lungs can slow down metabolism
Zee says there are many ways in which seeing light at night can affect our metabolism.
One possibility – supported by research – is that the presence of light can affect sleep quality, however, this study did not find an effect on the observation of people in the room. kukui. In fact, participants often expressed the feeling that they slept well.
The researchers also measured levels of melatonin, a hormone that helps regulate circadian rhythms and promotes sleep. Melatonin is often depleted during the day and wakes up at night.
Studies show that artificial lights at night can lower melatonin levels, and scientists have found a link between melatonin depletion and certain diseases, such as cancer and stroke. diabetes. Even here, the study found no evidence that melatonin levels were lower among those who slept with light.
“That means there isn’t enough light at the level of light going through the eyes to suppress melatonin,” Zee says.
However, Zee and his team believe this small light is enough to awaken the loving hand of the autonomic movement system – whether it is the body’s responsibility or the flight response. It is thought that this cools during sleep as the body moves in a parasympathetic state, when the body’s heart rate and breathing decrease.
Alterations in cardiovascular function indicate that a small amount of light is sufficient to change the nervous system to a more active and alert state.
“It was as if the brain and heart knew the lights were on, while that person was sleeping,” Zee said.
Learning is an important example of how seeing too little light can interfere with our sleep patterns, says Dr. Chris Colwell, whose lab at UCLA studies the underlying functions of circadian rhythms.
He said the information was useful because the autonomic nervous system is the daily organism.
“There’s a lot of work that’s planned to be done so we can get a good night’s sleep and the autonomic system balance fixes that,” Colwell said.
This effect on the nervous system is not “dramatic” – it doesn’t seem like people are waking up – but Colwell says of it: “You don’t want to do it when you’re trying to get a good night’s sleep. the night. “
The risk of heart disease increases
The study’s findings on metabolic health are not surprising.
Colwell notes that there is a stagnant amount of research, as well as a large number of studies, showing that suppressing circadian rhythms makes it difficult to regulate blood glucose levels.
Some of these human studies have used brighter light – not when people are asleep. And while the findings of this research alone cannot predict what will happen in the long run, Colwell thought the tragic consequences combined: “It’s only been one night, so think if you always live that way? “
The body’s “big clock”, called the suprachiasmatic nucleus, is located in the brain, but there are parts and muscles around the body that have their own cellular time -storage properties. Cells in the pancreas that secrete insulin are one example. Disrupting the sleep-wake cycle can impair their ability to properly secrete insulin, which is what controls blood sugar.
“It increases the risk of diseases such as insulin resistance, diabetes and cardiometabolic problems,” Drs. Charles Czeisler, head of the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital in Boston and a professor at Harvard Medical School.
For example, a large -scale study found that more than 40,000 women who slept with a TV or flashlight were associated with a 17% increase in gaining 11 lbs in five years.
Cseizler’s own research looked at the metabolic effects of discontinuing circadian rhythms for longer than overnight.
In a published study, he and his colleagues concluded the adverse metabolic effects seen in their participants over a three -week period were due to stress. circadian rhythms – not due to lack of sleep.
“While we didn’t increase their exposure to artificial light at night, we didn’t see the negative effects of regular sleep on glucose metabolism,” he said.
This doesn’t mean that sleep doesn’t have any negative effects on health – it does – but it does say that it only shows the long -term effects of seeing light at night.
“People think when they’re asleep and unconscious, it’s not a physiological result, but that’s not true,” Cseizler said.