It looks like closing the blinds, drawing the curtains and turning all the lights off before going to bed is indeed a better proposition. A new Northwestern Medicine study has found that the exposure to even tolerable ambient lights during the sleep in the night time, compared to sleeping in a dimly lit room, harms the proper function of the heart during the sleep, as well as increases the insulin resistance the next morning.
The results derived in the study exhibits that just one night of exposure to moderate room lights during sleep can hamper the regulation of glucose and cardiovascular, which are the potential risk factors for the heart disease, diabetes and metabolic ailments, said Dr. Phyllis Zee, the senior study author and chief of sleep medicine at Northwestern University Feinberg School of Medicine, along with being a Northwestern Medicine physician.
It is essential for people to either totally avoid or minimize the amount of light exposure during sleep, Dr. Phyllis Zee added.
There is already evidence that light exposure during daytime increases heart rate by activating the sympathetic nervous system, which then propels the heart into beating faster and thus heightens the alertness, so as to handle various works that we do throughout the day.
The results indicate that a similar effect takes place when we are exposed to light during our nighttime sleep, Zee said.
Heart beat elevates and body can’t rest properly
Dr. Daniela Grimaldi, a co-first author and research assistant professor of neurology at Northwestern, said that our heart rate increases when we sleep in a moderately lit room. Although we are asleep, our autonomic nervous system gets activated because of the light, and that is not good. Generally speaking, our heart rate along with other cardiovascular parameters, are low at night and are higher during the day.
The human body has sympathetic and parasympathetic nervous systems that regulate the physiology during the day and night. The sympathetic nervous system is in command during the daytime while the parasympathetic system is in charge during the night, when it provides the entire body restoration and rejuvenation.
How light during night sleep leads to diabetes and obesity?
The investigators found in the study that the insulin resistance happened the next morning after people slept in a room with light. The insulin resistance occurs when the cells in the muscles, fat and liver don’t respond properly to insulin and are unable to utilize the glucose in the blood for energy requirements. As a result, the pancreas starts producing more insulin, which over time increases the sugar levels in blood.
A previous study that was published in the JAMA Internal Medicine diagnosed a large population of healthy humans who were exposed to light during sleep. They were more overweight and obese, Zee said. Now we are revealing a process that might be the basis to explain why this happens, Zee further said, while adding that it is affecting our ability to regulate glucose in the body.
Grimaldi said that the participants in the study were unaware of the biological changes their bodies went through at night, but the brain was able to sense it.
Exposure to artificial light during night sleep is not uncommon
Exposure to artificial light during the sleep at night is a common thing. The light comes either from the indoor light emitting devices or from sources outside the home. A noteworthy number of individuals, reaching up to 40 percent sleep with a bedside lamp on or with a light on in the bedroom or with the television turned on.
The relationship of light to health is double edged
In addition to sleep, nutrition and exercise, light exposure during the daytime is an important aspect of health, but during the night, even the modest intensity of light can bring about harm to heart and endocrine health, Zee said.
The study researched the effect of sleeping with 100 lux (moderate light) of light compared to 3 lux (dim light) in participants for a single night. The investigators found that the moderate light exposure orchestrated the body to go into a higher state of alert. In such a state, the heart rate increases along with the force with which the heart contracts and the rate at which the blood is pumped to your blood vessels for oxygenated blood flow.
Zee gave some tips for reducing light during sleep:
- Turn the lights off. If someone needs to have a light on (such as, for safety), keep the lights dim and closer to the floor.
- Color is a major component. Amber, red or orange light is less stimulating for the brain. Never use white or blue light and always keep it far away from the person sleeping.
- Blackout shades or eye masks are good a good option if outdoor light can’t be controlled. Move the bed in such a position that the outdoor light doesn’t shine on the face.
Is my room too light?
Zee says that if you’re able to see things clearly, probably the room is too light.
Journal Reference:
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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