I’m surprised, sometimes, at the number of people who watch TV right up until they roll over and go to sleep. It’s one of the reasons late-night talk shows exist. Some people take things a step further, leaving their TV on overnight. I’ll admit, I do like to fall asleep to YouTube videos — but I only ever put them on my phone or Nest Hub, both of which are far smaller than a TV and automatically dim their brightness to make things easier. A 55-inch TV can illuminate an entire room, so for me, it barely matters if it’s playing Commando or The Joy of Painting.
Is it really that harmful to your sleep patterns to watch TV late at night, though? Does blue light make as much of a difference as some groups claim? You probably have a sense of the answer, but the details are a little more complex, and there can be factors far worse than light keeping you awake. There are also steps you can take to limit the impact of watching something at night, if you want to indulge the way many of us do.
The effects of light on sleep
It’s not just your phone or TV wreaking havoc
Human evolution hasn’t yet adapted to modern technology, which isn’t surprising, given how slowly it normally works. This comes to mind because of the link between light and circadian rhythm, the body’s internal clock. Everyone has a slightly longer or shorter rhythm, but roughly aligned with the 24 hours in a day.
It’s been established for decades now that daylight is instrumental in keeping circadian rhythms in sync. Specifically, exposure suppresses the release of melatonin, a hormone that regulates your rhythm and lets you sleep. Johns Hopkins notes that melatonin doesn’t directly put you to sleep — rather, it puts you into “a state of quiet wakefulness” that makes sleeping easier.
Historically, this was all well and good when there were no artificial light sources except fire. Once electricity entered the picture, however, it became possible to keep lights on well into the night without wasting candles, fuel, or firewood. Now, of course, we’re shoving a variety of screens in front of our faces, ranging from TVs through to phones, tablets, and AR/VR headsets.
When it comes to TVs, the problem is that most models rely on LED backlights, which emit quite a lot of blue light.
According to Harvard Medical School, any level of light at over 8 lux — a lux being one lumen per square meter — is enough to affect melatonin levels. That measurement may not mean much to you, but it’s only twice as bright as most nightlights, and probably dimmer than most of the lamps and ceiling lights you switch on. You can see how modern life would throw off your circadian rhythm, even without bringing TVs into the equation.
Some wavelengths of light have more impact than others, blue being the worst. A study cited by Harvard found that, after exposure for 6.5 hours, blue light suppressed melatonin for approximately twice as long as green light, skewing circadian rhythms by 3 hours versus green’s 1.5. The effect is such that a University of Toronto study found that simply filtering out the blue spectrum in bright light could result in the same hormone levels as someone exposed to a dimmer, unfiltered light.
When it comes to TVs, the problem is that most models rely on LED backlights, which emit quite a lot of blue light. In fact, many backlights are explicitly blue, since this is preferable over white for filtering or conversion to other colors. Technologies like MicroLED and RGB mini-LED have dedicated red and green backlights, yet just about any panel type — OLED included — is going to generate a fair amount of blue output, since it’s necessary for color accuracy.
Why your TV isn’t the whole story
Look at the broader picture
All that data would seem to foist the blame for bad sleep on light, with having a TV turned on compounding the effect of LED light bulbs. Some people are not only adjusted to having a TV on late at night, however, but actually dependent on it as a source of comfort. So what gives?
The answer is that a variety of other factors can have as much or more impact than light. Unfortunately, I have problems with chronic anxiety, and those can interfere not just with getting to sleep, but staying asleep. I’m sure that sometimes, watching EUC videos or Best of the Worst episodes doesn’t help — but if they distract me, they can reduce my anxiety enough to overcome the downsides of a shining display. Even if you don’t have a chronic condition, you might be kept up by short-term stress.
It’s also important to pay attention to sound and temperature. Some people are more sensitive to sound than others — so while some of you might be able to fall asleep during the middle of an action movie, others (myself included) may have trouble with dialogue at normal levels. Everyone also has different comfort levels for temperature, although Cleveland Clinic suggests that your bedroom should normally be cool, between 60 and 67F (15 and 19C).
Let’s not forget the effects of adrenaline. Owing to time constraints, I usually do my weightlifting a few hours before going to bed, and sometimes the rush lasts long enough that it’s only just tailing off when I tuck in. But even something less intense can have an effect, such as an exciting party, or finally beating that boss in Sekiro on your Steam Deck.
What should you do to minimize the effects of your TV?
Including tips for the stubborn
Harvard’s ideal recommendation is that you stop looking at any bright screen 2 to 3 hours before going to bed, your TV included. That might mean taking a walk, getting chores done, or reading a book, preferably on paper or an e-ink tablet.
Some of us don’t have much spare time, however, so if we want to watch a movie or play a game, there may not be much choice but to intrude on that recommended window. And as I’ve suggested a couple of times, watching video can occasionally provide necessary psychological comfort.
Thankfully, there are steps you can take to mitigate your TV’s effects without abandoning it. Many TVs have “night” modes that will automatically reduce brightness and/or blue light levels. One of the better implementations is Samsung’s EyeComfort Mode, which relies on both sunset schedules and ambient light detection. Your TV’s internal or external speakers may also have some sort of audio equivalent that caps volume spikes while keeping dialogue intelligible. Sonos soundbars, for instance, have a Night Sound option in their mobile app.
Many TVs have “night” modes that will automatically reduce brightness and/or blue light levels.
If you’re prone to falling asleep with your TV on by accident, try triggering your TV’s sleep timer. This should prevent your TV from waking you up later, which is better than nothing.
Lastly, remember that controlling light exposure is about cumulative amounts, not just the worst sources. If you have smart lights, it’s best to have them shift to warmer tones at night, and a dim red for anything left on while you sleep. Likewise, take advantage of night modes on your other devices — those include Night Shift on Apple products, Night Light on Windows PCs, and the various equivalents on Android phones and tablets. It may be less than ideal to be staring at screens right until you close your eyes, but if you can keep brightness and blue levels in check, it can substantially reduce the damage.
