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This One Habit May Be Wrecking Your Sleep, According to New Research

If you’ve been wondering why you’re waking up groggy and still sleepy, this tip could change everything.

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Are you completely ruining your sleep when you head to bed at night? The key to a better night’s sleep just might be as easy as making one small tweak. According to new research, your sleep environment might feature a critical mistake – one that can prevent you from getting truly restful, effective sleep. 

Here’s what you need to start doing before you climb into bed.

Keep light out of your bedroom – seriously!

If you’re leaving your blinds open while you sleep or, even worse, letting the TV stay on all night, you’re completely ruining your sleep. Complete darkness with no interference is the best way to sleep, and if you aren’t blocking out light, you could be having a big impact on your health (and how restful your slumber is).

A study published in Proceedings of the National Academy of Sciences suggests that letting light sneak into your bedroom can have a noticeable negative effect on your sleep. Researchers from Northwestern University tested the effects of varying levels of light exposure while sleeping. They exposed participants to either 100 lux (moderate light) or 3 lux (dim light) during one night of sleep. And their results showed that moderate light exposure has a direct impact on how you sleep – and how your body functions.

Those exposed to moderate light while sleeping had bodies in a higher alert state. Their heart rate increased, the force with which the heart contracts increased and the speed of conducting blood into blood vessels and keeping blood flowing increased. Essentially, the presence of moderate light activated the autonomous nervous system during sleep. Typically, while you’re asleep, your heart rate and other cardiovascular activities are lower; sleeping in a moderately-lit room seemed to make the body think it was daytime, leading to changes in its usual patterns.

Additionally, as one of the study’s co-authors, Dr. Daniela Grimaldi, told Science Daily, the participants’ brains showed unusual activity during sleep. Even if the participants were soundly asleep, their brains were behaving as though they were in light, fragmented sleep. That, in turn, suggested that those exposed to light during sleep weren’t actually reaping the benefits of a good night’s rest.

But the health effects didn’t end there. Researchers also noticed that the participants’ insulin resistance increased the morning after sleeping in a room with exposure to light. Increased insulin resistant means the body can’t use blood glucose as energy – and, as a result, your body creates more insulin. The long-term impacts of this process can put you at a potentially higher risk for health conditions like diabetes. 

And while all of these biological changes were taking place during sleep, the study’s participants had no idea. 

Light exposure while you sleep can have a surprising impact on your health

You might think you’re sleeping in total darkness, but the reality is that light can sneak into your bedroom in some small, seemingly insignificant ways. If you have devices in your bedroom that emit light all night long – like a glowing clock, a nightlight or your TV – or can see light from your bedroom window, that illuminating glow could be affecting your health. Even something as innocuous as a nearby street light that peeks through your blinds can have an impact. 

In fact, the study’s researchers note that just one night of exposure to moderate light while you’re in bed can have a surprisingly strong effect. Just one night of sleeping with light can hinder your natural glucose usage and production and alter cardiovascular regulation. With regular light exposure during sleep, you might potentially put yourself at an increased risk for diabetes and metabolic syndrome (which is linked to obesity). 

So, to ensure you’re truly getting a restful, restorative night of slumber, you’re going to want to close your curtains tightly, slip on an eye mask and keep your light-emitting devices face-down or turned off. 

How can you tell if you’re letting too much light into your bedroom while you’re sleeping? If you can see clearly in the “dark” you likely need to tone it down. The darker your bedroom, the better your sleep environment – and the restorative work your body can perform.