How often do you fall asleep with the lights on? I’m sure we’ve all done it at some point. Sometimes it just happens— especially if you’ve ever taken an accidental catnap on the couch when you meant to only rest for a moment. But if you regularly sleep with the lights on, you may want to reconsider that.
New research has come out about the potential negative effects that sleeping with lights on can have on your body. And while electricity has definitely made our lives easier and more convenient, this unfortunately isn’t good news for your sleep.
It may seem odd to sleep with lights on, but it’s actually a lot more common than you may think.
Do People Actually Sleep With The Lights On?
Yes! And we’re not just talking about a night light either. It’s common for people to fall asleep with some kind of light on, from bedside lamps to ceiling lights. In fact, 60 percent of Americans watch TV right before bed. And 61 percent of them fall asleep with the TV on.
Why Do People Sleep With Lights On?
We’ve all fallen asleep on the couch with the TV on. And normally when you doze off like that, it’s typically an accident. But people may go to sleep with lights on for a number of reasons. Here are a few of them:
- They’ve just watched a scary movie. According to one survey, 36 percent of people who watched horror movies at night reported sleeping with the lights on that night.
- It’s comforting, especially if they’re afraid of the dark. 32 percent of Americans claim that the dark makes them feel uneasy, while 29 percent of people say they’re simply afraid of the dark.
- They need a path to the bathroom. Whether it’s because of a medical condition or too much to drink before bed, who hasn’t had to get up and use the bathroom during the night? If it happens often enough, it may make sense to keep a well-lit path to prevent any stumbles, falls, or stubbed toes.
- Your bed partner keeps a light on. Sharing the bed is full of compromises, but if your partner’s book light, table lamp, or TV-watching is ruining your sleep, don’t ignore it! Like in every relationship, communication is key to achieving restful and harmonious sleep with a partner.
Why You Shouldn’t Sleep With The Lights On
Nighttime light exposure makes it difficult for your brain to “turn off” and help you get the deep sleep you need to feel rested in the morning.
Without those deeper sleep stages, your sleep is of poorer quality, which can have some negative effects on your body and your brain. Some of these include:
- It’s bad for your mental health— sleeping with lights on can make you moody, irritable, and has even been linked to depression.
- It’s bad for your physical health— one study found that obesity in women was more prevalent if they slept with the lights or the TV on. Your sleep and your weight are connected— the less you sleep, the more food you’re likely to eat the next day.
- It can make you more accident-prone, because poor sleep impacts your focus, concentration, and can make you more likely to take unnecessary risks in your day-to-day life.
- You’re more likely to get sick. A good night’s sleep is important for a healthy and robust immune system. Poor sleep can not only make you more likely to catch a cold, but it can make you more vulnerable to serious chronic health problems.
This is very important to know before going into these new studies. Speaking of which…
New Study Finds Surprising Consequences to Sleeping with Lights On
I’ve written a lot about the effects that blue light has on your sleep, but it’s important to consider how exposure to all kinds of artificial light can impact your sleep. In fact, a recent study published in Proceedings of the National Academy of Sciences explored how your sleep environment affects you during sleep. What they found was interesting— sleeping with lights on may contribute to heart disease and diabetes.
This study aimed to strengthen the results of a previous study, where researchers found that nighttime light exposure was correlated to obesity in women. I briefly mentioned that study earlier. It also aimed to see if acute light exposure during sleep adversely affects how your body maintains its blood glucose.
They also wanted to identify a specific cause for these issues— whether it was because of poor sleep quality, melatonin suppression, or because of sympathetic nervous system activation during sleep. As it turns out, the latter is a major culprit.
“Fight or Flight” vs. Light
Researchers observed 20 healthy young adults who slept in a lab for two nights. Half of the study’s participants slept with a dim light— like a night light— for those nights. The other half slept with a brighter light— similar to leaving their ceiling lights on. They then slept with a dim light the next night.
The researchers found that the participants that slept under the brighter light experienced some interesting effects. Those participants experienced a heightened sense of alertness when their bodies were supposed to be resting, along with a faster heart rate. Their ability to effectively use insulin was also reduced.
As well as increased heart rate, these participants also had lower overall heart rate variability (HRV) compared to those who slept in dim light. Heart rate variability is when the amount of time between each heartbeat changes slightly. This change in HRV was also associated with brief periods of higher insulin resistance.
The heightened alertness was because the participants’ sympathetic nervous system (SNS)— which triggers the fight or flight response— was activated while they were trying to sleep. In turn, these changes in their resting heart rate impacted their insulin resistance too.
How Bright Light Affects Your Sleeping Brain
Overall, participants who slept under the bright light spent more time in N2 sleep, and less in slow-wave and REM sleep. I talk more about these sleep stages in my article about what your brain does during sleep. If you want to learn more, I recommend reading it when you finish this one!
Too much light exposure at night can also inhibit your body’s natural melatonin production and prevent you from getting a good night’s sleep. This is why it’s so important to nighttime limit blue light exposure. Interestingly enough though, melatonin suppression wasn’t a factor in these findings. Researchers found that melatonin levels were consistent across all participants, regardless of what kind of light they slept in.
Study co-author Daniela Grimaldi, MD, PhD, assistant professor of neurology and sleep medicine at Northwestern University said “The brighter the light and closer it is to the sleeping person, the higher the risk that the light will activate physiological responses in the brain and body that can potentially harm health.”
However, it’s important to note that this study observed a small pool of participants over a very brief time period. So more research is definitely needed to make more sense of the possible connection between sleeping with lights on, heart disease, and diabetes.
Electric Light May Be Disrupting Your Circadian Rhythm
Another recent study observed the connection between artificial light, sleep disturbance, and your circadian rhythm. Published in PLOS Biology, the study found that the light you experience each day heavily influences your body’s natural rhythm. In short, excessive exposure to electric light and reduced exposure to natural light can lead to sleep disruption and potential circadian rhythm abnormalities.
This can largely be attributed to what’s known as melanopsin.
What is Melanopsin?
No, that’s not a typo. Melanopsin isn’t the same thing as melatonin, but they are related.
Light affects human sleep patterns through a unique cell in your eyes. These cells contain a light-sensitive protein called melanopsin. It’s most sensitive to blue light— remember, blue light helps wake you up in the morning and keeps you awake during the day. But excess blue light makes it much harder to get a full night of quality sleep.
When the cells in your eyes activate melanopsin, it actually suppresses melatonin production and helps keep you awake. Again, this is fine when you actually want to be awake, but this can be a real problem at bedtime.
So What Kind of Light Should I Use?
The study provides solid metrics for recommended light per day— but unless you’re already well-versed in light-measuring units, it ultimately isn’t very practical for the everyday consumer. So let me sum it up for you.
When it comes to daytime light indoors, the study recommends that indoor light should mimic natural daylight as closely as possible. You should also open up your curtains and blinds, and let some of that natural daylight in each morning.
In the evening— at least 3 hours before bedtime— indoor light should be significantly dimmer. And of course, at bedtime, your sleep environment should be as dark as possible.
This may seem a little complicated. But with some easy changes, it really isn’t.
Blinded by the Light? How to Protect Your Sleep From Electric Light
So if electric light during both night and day can ruin your sleep, what are you supposed to do about it? Don’t stress— you don’t need to throw out all your lightbulbs and live by candlelight. Here are some easy ways to make sure electric light won’t ruin your rest.
- If you must use a nighttime light, use a light with a red or yellow hue. These light colors won’t inhibit your body’s natural melatonin production like blue light will. On that note…
- Limit blue light exposure before bedtime. If you need to use your devices before bed, consider using blue light blocking glasses, like my Sleep Doctor Glasses. Just make sure they have amber-colored lenses— these are the best for blocking out blue light.
- Get plenty of natural light during the day, especially first thing in the morning. This helps your body stop melatonin production, wakes you up, and helps keep your circadian rhythm running smoothly. You can also use a light therapy lamp like those from Circadian Optics to help jumpstart your system each morning.
- Use an eye mask or blackout curtains to block out all artificial light or ambient light. This is especially helpful if your bed partner keeps an extra light on before bed, or if you do shift work and sleep during the day.
- Reconsider watching TV before bed. In the past, I’ve said it’s okay to watch TV while falling asleep. However, I may reconsider that recommendation after reading those new studies! If you watch TV before bed, you should really use the sleep timer to make sure that the TV won’t affect your sleep quality or wake you up during the night.
Lights Out For Better Sleep
I always say that light is medicine— getting the right amount of the right light can do wonders for your health and your rest. But with near-constant exposure to electric light— from electronic devices to overhead lights— it can have potentially serious effects on your ability to get a good night’s sleep.
But don’t worry, you don’t have to live in darkness to protect your rest. You can still enjoy the ease and convenience of electric light and electronics without depriving yourself of the sleep you need.
Michael J. Breus, PhD, FAASM
The Sleep Doctor
Michael Breus, Ph.D - The Sleep Doctor is a Diplomate of the American Board of Sleep Medicine and a Fellow of The American Academy of Sleep Medicine and one of only 168 psychologists to pass the Sleep Medical Specialty Board without going to medical school. Dr. Breus is a sought after lecturer and his knowledge is shared daily in major national media worldwide including Today, Dr. Oz, Oprah, and for fourteen years as the sleep expert on WebMD. Dr. Breus is the bestselling author of The Power of When, The Sleep Doctor’s Diet Plan and Good Night!