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Close the blinds, draw the curtains and turn off all the lights before going to bed. Exposure to even moderate ambient lighting during nighttime sleep impairs cardiovascular function during sleep and increases insulin resistance the next morning, reports a Northwestern Medicine University study.
“The results of this study show that a single single night light exposureeven modestly, to impair glucose regulation and the cardiovascular system, which are risk factors for heart disease, diabetes, and metabolic syndrome,” said study lead author Phyllis Zee. That’s why, she stresses, “it’s important for people to avoid or minimize light exposure during sleep.”
Exposure to light during the day is known to increase heart rate through activation of the sympathetic nervous system, which activates the heart and increases alertness to meet the challenges of the day.
“Our results indicate that a similar effect also occurs when light exposure it takes place during nighttime sleep,” says Zee. The heart rate increases in a bright room and the body cannot rest properly.
Daniela Grimaldi, co-author of the study, explains that “even if you are asleep, the autonomic nervous system is activated. That’s bad. Typically, heart rate, along with other cardiovascular parameters, are lower at night and higher during the day.”
nervous systems sympathetic and parasympathetic They regulate our physiology during the day and at night. The first during the day and the parasympathetic it is supposed to do it at night, restoration occurs throughout the body.
The researchers found that insulin resistance occurred in the morning after people slept in a lighted room. Insulin resistance occurs when cells in your muscles, fat, and liver don’t respond well to insulin and can’t use blood glucose for energy. To compensate, the pancreas produces more insulin. Over time, the blood sugar level rises.
An earlier study published in JAMA Internal Medicine that looked at a large population of healthy people who were exposed to light during sleep showed that they were more overweight and obese
“Now we show a mechanism that could be key to explaining why this happens,” Zee said. “We showed that it affects the ability to regulate glucose.”
The study participants were unaware of the biological changes that occur in their bodies at night.
“But the brain perceives it,” Grimaldi added. “The physiology of sleep does not rest as it should”
The problem is that exposure to artificial light at night during sleep is quite commoneither from devices light emitters inside or from sources outside the homeespecially in large urban areas. A significant proportion of individuals (up to 40%) sleep with a bedside lamp on or a light in the bedroom and/or keep the television on.
“In addition to sleep, nutrition and exercise, light exposure during the day is an important driver of health, but at night we show that even low light intensity can impair measures of heart and endocrine health,” Zee points out.
The study tested the effect of sleeping with 100 lux (moderate light) compared to 3 lux (dim light) on participants for a single night. The researchers found that moderate light exposure caused the body to enter a state of alert higher. In this state, your heart rate increases, as does the force with which your heart contracts and the speed with which blood is conducted to your blood vessels to flow oxygenated blood.
“These findings are important especially for those who live in cities, where indoor and outdoor exposure to nighttime light is becoming more widespread,” says Zee.
So how should we sleep? Zee advises not to sleep with the light on and, if necessary, to have a dim light and to be closer to the ground, and never be white or blue, better amber or a red/orange light that are less stimulating to the brain.
In addition, it is also advisable to completely lower the blinds or use blinders if the outside light cannot be controlled.
“If you can see things very well, there’s probably too much light,” Zee concludes.
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