LivingDo you want to sleep better? Turn off the...

Do you want to sleep better? Turn off the lights and lower the blinds

Do you like to sleep with a little light at night? Do you leave the television on while you sleep? Badly done. Scientists at Northwestern University in Illinois say that not completely blocking out light when we sleep can raise our sleeping heart rate to near daytime levels and affect how the body responds to insulin in the morning Next. Both of these factors could potentially increase the risk of heart disease and diabetes, suggests the new study published in the journal Proceedings of the National Academy of Sciences.

It is harmful to the body

The researchers found that even a small amount of light can affect cardiovascular function while you sleep and increase insulin resistance upon waking.

There was already evidence showing that exposure to light during the day increases heart rate through activation of the sympathetic nervous system, which speeds up the heart and increases alertness to face the challenges of the day.

“The results of this study demonstrate that a single night’s exposure to moderate room lighting during sleep can affect glucose and cardiovascular regulation, which are risk factors for heart disease, diabetes, and metabolic syndrome, ” Phyllis Zee explained. , chief of sleep medicine at Northwestern University School of Medicine and lead author of the study. “It’s important for people to avoid or minimize the amount of light exposure during sleep,” Zee added.


In the study, the researchers compared the impact of sleeping in moderate light , defined as 100 lux , with sleeping in low light, 3 lux for one night (one lux is the volume of light produced by a candle measured one meter away). ). For comparison, in an office, the volume of light usually ranges between 50 and 500 lux.

To do this, the volunteers, 10 adults, slept in different phases: one night in low light conditions and another night in moderate light . As a control group, another group of 10 people slept in low-light conditions for two nights in a row.

They found that people who were exposed to 100 lux while sleeping had a higher heart rate compared to those in the dim light group.

While the experiment participants were unaware of the biological changes in their bodies overnight. “But the brain detects it,” said Daniela Grimaldi, co-author of the work. “It acts like the brain of someone whose sleep is light and fragmented. Sleep physiology isn’t resting like it’s supposed to.”

“Even though you are asleep, your autonomic nervous system is activated. That’s bad. Typically, your heart rate along with other cardiovascular parameters are lower at night and higher during the day.

Considering that around 40% of people sleep with a night lamp or with the television on , their findings could have broad health implications.

“These findings are important in particular for those living in modern societies where exposure to indoor and outdoor nighttime light is becoming more widespread.”

Poor sleep on a regular basis has been linked to a multitude of medical problems, including obesity and depression, so remember: at bedtime, it’s best to close the curtains, blinds, and turn off all the lights. And if you can use a sleep mask, all the better.

Ivy C. Mason, Daniela Grimaldi, Kathryn J. Reid, Chloe D. Warlick, Roneil G. Malkani, Sabra M. Abbott, Phyllis C. Zee. Light exposure during sleep impairs cardiometabolic function.  Proceedings of the National Academy of Sciences, 2022; 119 (12) DOI: 10.1073/pnas.2113290119

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