Why falling asleep with even a little light can negatively impact your health

Sleeping in a dark room is important for sleep hygiene, yet you may not be following the rule as closely as you think you are. Whether it’s a curtain that doesn’t completely cover the width of the window, a door left ajar with the hallway light on, or blue light from your devices, all these sources of light can mess up your circadian rhythm. In fact, new research is pointing to a new set of problems nighttime light can have on your health. Here’s what you need to know about light exposure and its adverse effects on your wellbeing.

If you’ve ever woken up feeling tired even if you didn’t wake up in the middle of the night, your sleep environment may be the culprit. That’s because light — and specifically artificial light — can mess up the phases of your circadian rhythm along with the production of melatonin.

Research published in the Journal of Physiology looked at the relationship between light and sleep and found that even brief light exposure (as little as 12 minutes) suppressed melatonin production and made people feel less tired at bedtime. Melatonin is a natural hormone your body produces from the pineal gland. Darkness aids in melatonin production as well as the transition to sleep. When light enters the equation, melatonin isn’t produced as efficiently as it would be in a completely dark room.

Your body doesn’t only produce melatonin at night, however. And making sure you’re churning out the appropriate levels morning through evening is key to getting a good night’s rest. By measuring melatonin levels throughout the day with an at-home test like Base, you can see how you’re doing and whether you need the support of a supplement and/or lifestyle interventions. 

While light exposure may be the reason you aren’t sleeping as well as you should be, over time it can also impact your heart health as well as metabolism. A study conducted by researchers at Northwestern University examined 20 healthy adults between 18 and 40 years old. Participants who slept in a room with overhead lighting (100 lux of artificial light) had less rapid eye movement sleep (REM), the stage of sleep responsible for memory, brain development, and emotional processing. This group also had a higher heart rate and lower heart rate variability - one of the warning signs for poor heart health because it shows your heart can’t handle changes and fluctuations easily. This combined high heart rate plus low variability also influenced insulin resistance the next morning, increasing the risk of leading to metabolic disease such as diabetes.

One study published in the Journal of Athletic Training discovered that when 10 athletes received 30 minutes of red-light therapy every night for 14 days they slept better and increased melatonin production. The key here is that red light is a helpful tool to use before bed, not while you sleep. When choosing a light, it’s recommended to choose one < 100 lux as to not disrupt your circadian rhythm and help your melatonin production kick into high-gear for the evening. If you’re wondering how your bedroom lighting may be impacting hormone levels like melatonin, use Base’s sleep testing plan to see if your levels are appropriately increasing enough at night.

Falling asleep in a dark, quiet room probably sounds like a dream. In some cases, it just might be. Maybe you share your bed with a partner who likes to fall asleep with the TV on or you like to leave your door open and/or using a nightlight in case your kids pay you a middle-of-the-night visit. If you can’t avoid all light while you sleep, try these hacks to keep melatonin levels balanced.

Light enters through the retina and makes it to the suprachiasmatic nucleus (SCN), which is located in the hypothalamus - the area of the brain responsible for sleep. This is what helps set the sleep-wake cycle, and one of the reasons why you may have difficulty falling asleep after exposure to bright or ambient light. In order to minimize light reaching your SCN, you have to block it from getting into your eyes. Tuck in with a high-quality sleep mask to prevent any light in the room from affecting your circadian rhythm and melatonin production.

Light exposure at night isn’t such a bright idea, but waking up to natural light is not only a great way to start the day - it’s helpful in maintaining melatonin levels. One study in Current Biology discovered that after a week of natural light exposure circadian rhythms were pushed up two hours earlier, with melatonin levels steadily rising from sunset through the evening and decreasing in the morning. Start your day with a cup of coffee outside or a quick walk to soak up some vitamin D and keep your sleep schedule on track.

One of the biggest sleep sabotagers is in the palm of your hand - your phone. That’s because the blue light your phone emits makes your brain think it’s daytime, suppressing melatonin and causing sleep troubles to go with it. To help limit temptation and prevent feeling groggy in the morning don’t bring your phone into the bedroom at all if you can help it. If you need it, set the Do Not Disturb an hour before bedtime to eliminate notifications and put a stop to mindless before-bed scrolling.

Melatonin can help you fall asleep and can be helpful for short-term use. Yet oftentimes it’s not just melatonin that your body is lacking in order to fall asleep. Depending on your own personal needs, taking a supplement with melatonin, magnesium, and vitamin B complex may help you get a deeper sleep as your circadian rhythm resets to its proper time frame. Base sleep testing can help you identify what you really need and in what amounts. Stay on top of how much or how little melatonin your body’s naturally producing on an average day, and see how these levels shift when implementing healthy sleep hygiene habits and/or supplementation.