Sleeping with lights turned out to be bad for the heart

(ORDO NEWS) — A new study by American scientists has shown that exposure to even moderate lighting during a night’s rest, compared to sleeping in a dimly lit (actually dark) room, harms the cardiovascular system, and can also lead to diabetes and obesity.

Exposure to artificial light at night while sleeping is a common occurrence these days. The light may come from special nightlights, electronic devices, sources outside the home, street lighting, especially in large urban areas.

A significant proportion of people (up to 40%) sleep with a bedside lamp on, a nightlight on, a bedroom light on, or a TV on.

In a new study, researchers at Northwestern Medical Center (Illinois, USA) examined the overall effects of sleeping in a moderately lit room (100 lux) versus sleeping in dim lighting (three lux) for one night.

For comparison: according to sanitary rules (SanPiN), the lighting standards for the office are 300 lux, for living rooms – 150 lux, and in the elevator shaft – five lux.

As a result, the scientists found that moderate exposure to light caused the body to go into a state of “high alert” even during sleep. This condition increases the rate and force of heart contractions, as well as the rate at which oxygenated blood enters blood vessels throughout the body.

“We have shown that your heart rate increases when you sleep in a room with moderate lighting,” said Dr. Daniela Grimaldi , co-author of the study and assistant professor of neuroscience at Northwestern University.

Even during sleep, the autonomic nervous system remains active. And this is bad. Typically, heart rate, along with other cardiovascular parameters, is lower at night and higher during the day.”

The autonomic nervous system is engaged in the regulation of internal organs and glands, is divided into sympathetic and parasympathetic nervous systems, the effect of which on the body is in most cases opposite.

The sympathetic increases metabolism and prepares the body for active actions during the day, while the parasympathetic regulates the functioning of the body during sleep, restoring its strength at night.

Violation of the cyclical operation of these systems can lead to serious disruption of the entire body. This violation was identified by American researchers. In addition to the effect on heart rhythms, they found that after sleeping in a relatively lit room, the participants developed insulin resistance the next morning.

Insulin resistance is a disorder of insulin metabolism in which muscle, fat, and liver cells do not properly respond to insulin in the blood and cannot use blood glucose for energy.

To compensate for this, the pancreas produces even more insulin. Over time, blood sugar levels rise, which is very similar to the symptoms of type 2 diabetes (only in this case, the disorder is chronic).

“The results of this study show that just one night of exposure to moderate room lighting during sleep can impair glucose levels and cardiovascular regulation, which are risk factors for heart disease, diabetes, and metabolic syndrome,” explains Phyllis Zee, senior author of the study.

Phyllis Zee , Head of Sleep Medicine at Northwestern University’s Feinberg School of Medicine and Physician at Northwestern Medical Center. “It is important for people to avoid or minimize exposure to light during sleep.”

An earlier 2019 study looked at a large group of healthy people exposed to light while sleeping. According to Dr. Zee, they were characterized by overweight and obesity.

“Now we are demonstrating a mechanism that could be fundamental to explaining why this is happening,” concludes Dr. Zee.

“We show that it affects your ability to regulate your glucose levels. These results are especially important for those living in today’s society, where exposure to indoor and outdoor nighttime light is becoming more common.”


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