New research from Northwestern University, published in the Proceedings of the National Academy of Sciences, shows that if you sleep with a light on — even a light so dim that you can’t read by it — it triggers your adrenaline to remain active during sleep. This leads to non-restorative sleep that can cause weight gain and lead to type 2 diabetes.

The study of 20 healthy adults found that just one night of sleeping with the lights on spurred changes in people's physiological functioning. Participants’ heart rates stayed higher during sleep compared to a night with lights off. And, by the next morning, they were churning out more insulin — a hormone that regulates blood sugar.

“The new Northwestern study shows that being stuck in adrenaline mode during sleep triggers insulin resistance, which translates as weight gain. So, this may be one more cause of the average 32 ½ pound weight gain commonly seen in patients with chronic fatigue syndrome and fibromyalgia,” says Dr. Jacob Teitelbaum. Teitelbaum says that poor sleep quality is a common symptom of people suffering from chronic fatigue and fibromyalgia.

Getting too much or too little sleep can lead to Alzheimer’s disease. A new study published in the journal JAMA Neurology examined the role of sleep in the accumulation of brain amyloid plaque buildup, cognitive performance, and other factors of healthy brain aging.

Poor sleep affects the immune system as well and has been associated with other conditions like increased risk for heart attack, obesity, stroke, and depression.  A study published in the journal Neurology reports that people who consistently sleep more than nine hours a night, take naps that are longer than an hour and a half, or who get poor quality sleep, have a higher risk of suffering a stroke.

It's well known that people need exposure to sunlight during the day, and darkness at night, to keep the body's circadian rhythms running optimally. Those rhythms, which are like 24-hour internal clocks, help regulate processes throughout the body — including sleep, metabolism, and hormone release.

But modern humans are exposed to all kinds of artificial light at night, and research has been pointing to the pitfalls. Exposure to blue light from glowing devices may be especially problematic: It suppresses the body's release of the sleep hormone melatonin, making us feel more alert when we should be unwinding.

Even the recent time change may have a negative effect on the quality of our sleep and well-being.

On March 15, the U.S. Senate voted to instate permanent daylight saving time to eliminate the twice annual havoc of changing our clocks. Many Americans objected to the move and health experts, including the American Academy of Sleep Medicine, stated that “Daylight saving time is less aligned with human circadian biology.” A 2019 study  concluded that an extra hour of natural light in the evening reduces sleep duration by an average of 19 minutes.”

To ensure a good night’s sleep and protect your health, Teitelbaum suggests wearing a sleep mask to black out any ambient light during sleep, which may make your rest more restorative, and maybe even help you shed a few pounds.

Here are other sleep-enhancing tips:

1. Follow a consistent sleep schedule. Try to go to sleep and wake up at the same time daily. You can’t make up for lost slumber on the weekend.
2. Avoid heavy meals, alcohol, and caffeine before bedtime. According to WebMD, foods that contain tryptophan, such as milk, nuts and seeds, bananas and honey can help induce sleep. Heavy, fatty foods disrupt digestion and sleep cycles,
3. Keep your environment serene. Remove all electronics and light sources from the bedroom and keep the temperature cool. The ideal temperature for sleeping is between 66 degrees Fahrenheit and 70 degrees Fahrenheit, says Sleep.org.
4. Meditate and exercise during the day. These activities have been shown to induce restful sleep at night.