In these stressful times, sleeping can be pretty difficult — and light is not your friend. According to a new study, sleeping in a room with light coming through is not only bad for your sleep, but it is also associated with a number of health problems. According to the new study, having light in the room increases heart rate and nervous activity over the entire sleep period, one study author told ZME Science.
Lights, lights everywhere
Having access to electricity is without a doubt one of the most impactful things in our society. If you think about, it’s a true wonder that electricity is so easily available that in most cities, there’s always light. Herein lies the problem: there’s always light.
We have light from bulbs inside our homes, we have streetlights, we have neon signs and of course, we have screens. For millennia, humans have generally followed the solar cycle of light, but this is no longer true — the lights we’ve let into our house are changing our sleep patterns, and according to new research, also affecting our health.
“We wanted to understand why there is an association between exposure to light at night with increased prevalence and incidence of weight gain and obesity. The objective was to understand how moderate levels of light during sleep affects cardiovascular and metabolic function,” said senior study author Dr. Phyllis Zee, chief of sleep medicine at Northwestern University Feinberg School of Medicine and a Northwestern Medicine physician, for ZME Science.
Exposure to artificial light during sleep is common, the new study says. Up to 40% of people sleep with a headlamp on or the TV or laptop, the researchers estimate. But sleeping in a room with even dim light is associated with an increased risk for heart disease and diabetes, the study found.
“The results from this study demonstrate that just a single night of exposure to moderate room lighting during sleep can impair glucose and cardiovascular regulation, which are risk factors for heart disease, diabetes and metabolic syndrome,” Zee added. “It’s important for people to avoid or minimize the amount of light exposure during sleep.”
While this is an observational study (it just observed a correlation and did not establish a direct cause-effect relationship), this fits well with previous studies.
We’ve known for some time that our bodies’ circadian clocks are influenced by light, and exposure to light reduces the secretion of melatonin, which makes your body feel more wakeful. While you may not realize it, light can reset your body lock, causing your heart rate to rise and preventing you from getting a good night’s sleep.
Light also interferes with our body’s sympathetic and parasympathetic nervous systems, which among other things, regulate the “fight or flight” response and manage stress and alertness. It doesn’t even have to be a lot of light for it to interfere with your sleep, researchers say.
“The most important finding is that one night of exposure to moderate levels of room light while sleeping with eyes closed increased heart rate and sympathetic activity during the entire sleep period, suggesting activation of the nervous system. In addition, in the room light condition, a higher amount of insulin secretion was required to normalize glucose level following ingestion of a bolus of glucose – consistent with higher insulin resistance,” Zee added.
“We showed your heart rate increases when you sleep in a moderately lit room,” said Dr. Daniela Grimaldi, a co-first author and research assistant professor of neurology at Northwestern. “Even though you are asleep, your autonomic nervous system is activated. That’s bad. Usually, your heart rate together with other cardiovascular parameters are lower at night and higher during the day.”
Sweet dreams are dark
This isn’t the first study to find an association between sleep time lights and health problems. A previous study found that healthy people who are exposed to light during sleep are more likely to be overweight and obese, and this new study also suggests how this could happen.
“Now we are showing a mechanism that might be fundamental to explain why this happens,” Zee said. “We show it’s affecting your ability to regulate glucose.”
This may be due to insulin resistance. Basically, insulin resistance means the cells inside the body are unable or less able to respond to the amount of insulin they are receiving, and they can’t use glucose for energy. To make up for this, the pancreas starts producing more insulin, which in turn, raises blood sugar. The researchers found that after people slept in a room with light, insulin resistance spiked.
“In addition to sleep, nutrition, and exercise, light exposure during the daytime is an important factor for health, but during the night we show that even modest intensity of light can impair measures of heart and endocrine health,” Zee said.
Is there too much light in your room?
If you’re asking yourself this, then the answer is probably ‘yes’.
“If you’re able to see things really well, it’s probably too light,” Zee said.
So here’s what you can do to make sure your sleep goes undisturbed by light:
- Don’t turn on the light. Turn the screens and the lamp off. If you do want to use a night light, make it as dim as possible and leave it closer to the floor.
- Try to use red or orange light instead of blue or white light. The former are less stimulating for the brain, while the latter tend to make you more active.
- Use the shades. Light doesn’t only come from the inside, it also comes from the outside, and thick shades can prevent the light from coming in.
The study was published in PNAS.
