A new study out of Northwestern University has shown that exposure to even a small amount of ambient light at night can disturb your sleep, as well as harming cardiovascular function and increasing insulin resistance the next day.

“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,” said senior study author Dr. Phyllis Zee, chief of sleep medicine at Northwestern University Feinberg School of Medicine.

“It’s important for people to avoid or minimize the amount of light exposure during sleep.”

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Minimise light exposure for a better night’s sleep


The researchers study tested the effects of sleeping with 100 lux (moderate light) compared to 3 lux (dim light) in participants over a single night.

There was already evidence that light exposure during daytime increases the body’s heart rate by activating the sympathetic nervous system, heightening a person’s alertness so they are ready to meet the challenges of the day.

“Our results indicate that a similar effect is also present when exposure to light occurs during nighttime sleep,” Zee said.

The investigators found that moderate light exposure caused the body to go into a higher alert state, just like during the day. The heart rate increases, as does the force with which the heart contracts and the rate at which the blood is pumped through the blood vessels.

What’s more, investigators found that insulin resistance was present the morning after people slept in a light room.

Insulin resistance occurs when the body’s cells, especially cells in the muscles, fat and liver, stop responding as well to insulin, preventing them from using glucose from the blood as efficiently to produce energy. As a result, the pancreas makes more insulin and over time, your blood sugar goes up.

Lifting weights is the best way to get a good night’s sleep, fascinating new study

“It is increasingly recognized that getting enough sleep, particularly high-quality sleep, is important for health including cardiovascular health. Unfortunately, more than a third of Americans don’t get enough sleep on a regular basis,” says study author Angelique Brellenthin, Ph.D., assistant professor of kinesiology at Iowa State University in Ames, Iowa, in a press release

“Aerobic activity is often recommended to improve sleep, yet very little is known about the effects of resistance exercise versus aerobic exercise on sleep. Our study is one of the largest and longest exercise trials in a general adult population to directly compare the effects of different types of exercise on multiple sleep parameters.”

To study the relationship between various forms of exercise and sleep, researchers took nearly 400 adults who were considered either obese or overweight . All participants led largely inactive lifestyles, and showed high blood pressure.

The subjects were separated randomly into groups. One group served as a control group (no exercise at all), and three other groups (aerobic only, resistance only, or a mixture of aerobic and resistance exercises) were formed.

All groups stuck to their prescribed routines for a full year. Across all three groups participants engaged in supervised one-hour sessions three times a week. The combination group spent 30 minutes on cardio and another 30 on resistance exercises during each session.

Click here to read more about this fascinating study

The study builds on an earlier study which looked at a large population of people who had exposure to light during sleep. The study showed a clear link with being overweight or obese.

“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.”

The participants in the study weren’t aware of the biological changes in their bodies at night.

“But the brain senses it,” another of the study authors added.

“It acts like the brain of somebody whose sleep is light and fragmented. The sleep physiology is not resting the way it’s supposed to.”

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