Your Night Light May Be Slowly Killing You, a New Study Says

Photo credit: Malte Mueller - Getty Images
Photo credit: Malte Mueller - Getty Images

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  • Exposure to a moderate amount of light during nighttime sleep may significantly harm your health, according to new research.

  • Participants who slept in rooms bathed in light saw increased heart rates and a spike in insulin resistance.

  • Fortunately, we’ve got some great ideas for improving the quality of your sleep.

Think stress is causing your heart to race? There may be another culprit: your night light.

Even a small amount of ambient light from, say, a TV or bright exterior lights that filter in through a nearby window during nighttime sleep can negatively impact your health, according to a new study published March 14 in the journal Proceedings of the National Academy of the Sciences.

💤 Science is on our side. We’ll help you make sense of it all.

“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,” Phyllis Zee, chief of sleep medicine at Northwestern University Feinberg School of Medicine and a co-author of the study, says in a press release.

The researchers monitored patients who slept in moderately lit rooms (100 lux, or lumens per square meter) and dimly lit rooms (3 lux) over the course of one night and assessed how their bodies adjusted throughout the night and into the next day. Study participants who slept in rooms with a moderate amount of light went into a heightened state called sympathetic activation.

The autonomic nervous system, which regulates things like heart rate, pupil dilation, body temperature, and digestion, can be split into two categories: the sympathetic nervous system and the parasympathetic nervous system. During the day, the sympathetic nervous system regulates different functions that help the body prepare for activity and governs our body’s response to stress. At night, the parasympathetic nervous system helps the body rest, digest, and recuperate.

The added light triggered participants’ sympathetic nervous system, which should have been inactive, and kicked it into overdrive. Over the course of the night, the participants experienced elevated heart rates and a spike in how forcefully the heart contracts.

What’s more: the next morning, the participants showed signs of insulin resistance, meaning the cells in their muscles and fat began to reject insulin and weren’t able to properly process glucose to make energy. Over time, this spike in insulin resistance could lead the pancreas to produce more insulin, eventually leading to higher blood sugar levels and even type-2 diabetes, the authors say. (Previous studies have found that populations who slept in moderately lit rooms were more likely to be overweight or obese, according to the press release.)

“These findings are important particularly for those living in modern societies where exposure to indoor and outdoor nighttime light is increasingly widespread,” Zee says in the press statement. “If you’re able to see things really well, it’s probably too light.”

Sleep Tight...

Fortunately, there are a few great options to help keep the light out while you doze off. Here are some good tips to follow should you need to keep some sort of light on while you sleep.

Lights too bright?

  1. Install blackout curtains to keep stray rays away.

  2. Looking for a more cost-effective option? Sleep with an eye mask.

  3. If possible, try rearranging your furniture so your bed doesn’t face the light source.

  4. Finally, turn off your TV.

Need just a little bit of light?

  1. If you frequently get out of bed at night, opt for a motion-activated night light.

  2. Select red and orange-hued lighting over white and blue-hued lighting.

  3. Placement is key: make sure night lights aren’t directly visible from the bed.

💤 Sleep Better Tonight

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