How Light Affects Our Sleep
Most people are at least cursorily familiar with the concept of the circadian rhythm. For those who aren’t, the circadian rhythm refers to our internal, approximately 24-hour cycle of biochemical, physiological, and behavioral processes. Every living thing, from fungus to bacteria to plant to animal, has a circadian rhythm. External cues called zeitgebers (what a great word, huh?) help synchronize or alter our rhythms; they include temperature, nutrition, meal timing, social interactions pharmacological interventions (medicines, drugs), and, most prominently, the light/dark cycle of the earth.
Yes, light, or the lack thereof, plays an enormous role in the regulation of our cycles, especially our sleep cycle. For millions of years, light was an objective, exogenous measure by which organisms established behavioral patterns, hormonal fluctuations, and sleep cycles. Depending on the seasons, the position of the global axes, and the weather, you could pretty much count on light, bright days and deep, dark nights. Nocturnal hunters and scavengers took the lack of light to mean “eatin’ time,” while other animals (including humans) sought shelter and slumber when night fell. Daylight meant activity and safety (since we could, you know, see everything). Fire, then, wasn’t just about cooking and providing warmth; it also allowed humans a small sliver of daylight’s safety and security at night.
Before I go on, I need to make something clear. My regular readers will have already grasped this concept, but I think it’s a good idea to reiterate it. Though it’s tempting to place us humans on another plane of existence, apart from the mindless flora and fauna that share this world, we are animals. Sure, we’re smarter and more complex than the others, but we’re still subject to these exogenous zeitgebers worming their influential fingers into our subconscious and fiddling with our circadian rhythms. Our tendency to get sleepy when night falls isn’t a cultural relic; we didn’t consciously decide to start sleeping at night because it was too dangerous to be out in the dark. The culture of standard bedtimes arose organically, if you can even call it culture. Does the chirping of birds in the morning reflect cultural tendencies? Is “the early bird gets the worm” a standard axiom in avian academia? No – the early bird’s evolutionary niche decrees that it wake up bright and early in order to get food. It’s basic natural selection, and humans are the same way. We don’t decide to get up early. We get up early because of a complex pattern of environmental cues telling us to get up. Throughout our evolutionary development, handling business during the daytime was simply how we survived. We can’t escape nature.
But boy do we try.
The zeitgeber (can’t get enough of that word) with the biggest impact on our sleep cycle is light. Period. And it’s not just natural light that affects our sleep cycle, but also unnatural, manmade lights. That’s kinda how we operate, actually, as instinctual beings who often misinterpret “unnatural” because, well, our physiology isn’t exactly intelligent. It’s not sentient. It’s purely reactive. Blue light from a 10:00 AM sky, blue light from your computer screen at midnight – it makes no difference to our circadian rhythms. It’s all the same to our bodies, because for millions of years blue light meant daylight, not a late night blog comment section or reruns of The Daily Show. And it’s the blue light specifically that appears to monitor our sleep patterns the most.
Like insulin and inflammation, blue light is integral to our health – in the correct amounts. When we’re exposed to levels of anything in excess (or too little) of what we would have experienced for the bulk of our evolutionary history, problems arise. Blue light regulates our secretion of melatonin, the sleep hormone. Exposed to blue light, we limit the production of melatonin, and we stay alert and awake; in the absence of blue light, melatonin production ramps up, and we get sleepy. This system worked quite well for a long time. Reddish light from fire (our formerly primary source of nighttime illumination) has little to no effect on melatonin production, so sleep wasn’t disrupted when we relied on fire. These days, though, we’re subject to a steady barrage of blue light. During the day, blue light (natural or unnatural) isn’t much of a problem because we’re supposed to be awake, but at night, when we’re “supposed” to be getting ready to sleep, we tend to sit in front of blue light-emanating appliances, and our sleep suffers for it.
(An interesting note on how we respond to blue light. For years, scientists assumed circadian rhythm was set by sight (of light) alone. Person sees sky/LCD screen and the same visual system that allows colored vision determines the hormonal, behavioral, or other physical reactions to the light. It makes sense, but that’s not how it works. It turns out that there exists a second, more dominant system responsible for setting circadian rhythm based on light input. If a person’s sleep cycle depended purely on traditional color vision, we’d expect the blind to universally suffer from disrupted sleep. They do not, however, and this is explained by optical cells that express a photopigment called melanopsin. Unlike the standard rod and cone opsins, melanopsin doesn’t help us see. Instead, it reacts most strongly to blue light, and scientists think it’s the primary regulator of the biological clock and production of melatonin. In otherwise blind patients with intact melanopsin systems, blue light has a strong effect on their sleep cycles.)
Blue light has its place, of course. A British study found that blue light-enhanced white lights in the workplace improved alertness, performance, and even nighttime sleep quality in employees. That’s during the day, though, when blue light exposure is normal and expected. Nighttime exposure to blue light disrupts our sleep hormones. Television, computer screens, even digital clocks with blue numbers – they’re all common sources of late night blue light that can affect our production of melatonin.
Is blue light the only issue? It certainly appears to be the primary driver of circadian rhythm, but it’s not the only one. In a recent study, researchers found that while monochromatic blue light suppressed melatonin production via melanopsin stimulation, polychromatic white light (which includes blue light) stimulated melanopsin equally while suppressing melatonin to an even greater degree. Clearly, it’s not just blue light’s effect on melanopsin affecting our sleep cycles.
Still, blue light is the low-hanging fruit, and there are some simple steps you can take to mitigate its late-night effect on your sleep.
- Keep electronics usage to a minimum or completely eliminate blue light (alarms, TVs, laptops) after dark.
- Go to sleep earlier.
- Use candlelight (read how a fellow MDA reader gave this a try for 30-days).
- Keep your room as dark as possible and your sleeping quarters pitch black.
- Install F.lux (totally free) on your computer to cut down on blue light emissions.
- If you want to try a somewhat extreme experiment you could even wear orange safety glasses at night.
(Thanks to this thread on PaleoHacks for the last two tips.) Also, don’t forget to expose yourself to blue light during the day so that your cycle normalizes – it goes both ways, you know.
Does anyone have experience cutting out blue light exposure to great effect? Let the world know in the comments.
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Posted By: Mark Sisson
Hi there,
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Let me know if you’re interested.
Thanks.
I just can’t get to sleep early. No matter how hard I try.
Hi there!
As long as i can think i have trouble getting to sleep.
I want to exchange my normal bulbs to bulbs that are good for sleeping.
Now i am wondering what the right bulbs are:
- normal ‘nightlights’ in the store (has it blue light in it?)
- LED – lights – i guess they are also blue. Red LED lights?
- lightbulbs that are red (normal bulbs with red covers)
- only lights from lowbluelights.com?
I find it confusing. And i am starving for info. Are there books? Is there any forum or something that talks about this? The blue-light thing is pretty unknown, is it?
Thanks for the help!
I usually fall asleep in a few minutes in a dark environment but in a light room and with some sort of noise it takes maybe an hour for me to fall asleep.
Wow. I am now fully aware of just how much I’ve been screwing over my circadian rhythms.
Thanks so much for your post! I was reading about circadian rhythms at two in the morning on my laptop, then wondered why I was having all those sleep problems. =D
Hi adrenalin often wakes us up – in an effort to maintain blood sugar – the body will release this – so we do not die – often times eating a piece of fruti before bed, and/or if we wake up in the middle of the night – a piece of fruit then – we can go back to sleep – the time between our last meal and breakfast quaifies as starvation – so eating a food that balaned blood sugar beofre bed will help. Of course if the mind is spinning – learning to turn off the mind by concentrating on breath – helps also
I know some people that cannot sleep under any amount of light even if it is very little.
I cannot sleep even if there is a loptop running in my room. That’s really bad as I see some people sleeping on a bus in the middle of the day, how can they do that?
Well, I don’t know what to believe anymore, all the experts are saying something different.
“If you want to try a somewhat extreme experiment you could even wear orange safety glasses at night.”
That was something new for me. Checking that glasses right now.
Hi
Is there an equivalent to f.lux for the iphone ?
Great post btw.
Watch out for heavily scented candles, etc. They often emit toxic volatile organic compounds. Look for the clean-and-green ones if you’re planning to burn ‘em.
i’ve got a couple of questions-i just saw these bedside ott reading lamps that have led lights-i’m wondering how these would affect melatonin?
also, how about these crystal salt lamps-wondering how the light from those might affect melatonin?
i’m trying to figure out what the best light for reading right before bed would be-candles aren’t quite bright enough!
I have a desk lamp beside my bed with a florescent “bug-light” yellow bulb in it. Warms the room up like a fire and plenty bright enough to read by.
Turning on a bedside lamp at nighttime can block the stimulation of the pineal gland. This results in a continuous drop in the level of melatonin secretion. Exposure to light can help control the production of melatonin. Light therapy can be used to effectively regulate the levels of melatonin secreted by the pineal gland. This type of treatment can be used for treating sleeping conditions like insomnia or jet lag.
On the topic of sleep, check out this new piece in the Harvard Business Review – Sleep is More Important than food:
http://blogs.hbr.org/schwartz/2011/03/sleep-is-more-important-than-f.html
I spent nine months minding a farm house, without electricity: candles & gas cooking were what I had. two hours after sunset: nothing better to do than sleep! Of course, my days were filled with hauling water, long walks to pull noxious weeds & repair this & that around the place, or just exploring. Presently, I use 4 & 8 hour candles in candle lanterns. I also recommend three candle power for reading by. AS fro keeping the bedroom totally dark: only if you have street lights, which, IMHO, ought to be turned off at 10pm.
Does anybody know an app for iphone that could do the same as F.lux?
Thanks for this article! Ever since I started using candles at sunset, I’ve gotten lots more sleep! And now that I’m sleeping better I’m less tired, I have more energy, my hair has gotten more shiny and my vagina is much softer! My husband couldn’t be happier!!
That would be cool to be able to adjust our smart phone’s screen colors. You did see the post about the alarm clock app that senses your stage of sleep, yes? http://itunes.apple.com/us/app/sleep-cycle-alarm-clock/id320606217?mt=8
There is one for Android too (my phone) but I don’t remember the name now. You all have motivated me to seek it out again.
One of my biggest problems is waking in the wrong stage of sleep. If I am woken right after dream stage it takes me 5 hours to wake up. And try to wake me from a dream… good luck; you’re on you’re own! But if I wake up from a light sleep, it’s like I was fed Friskies that day.
I wonder if that app would do any good, though, since the phone has to be touching or very near you. Might as well sleep on top of your computer for all the EMF’s and radiation. My speakers go nuts when my phone’s trying to find a signal. Airplane mode would probably help a lot though.
Thanks a lot for all of your suggestions! I have learned a lot and am now typing on an orange screen, in a room with some serious romantic lighting. LOL!
As an added bonus, I discovered previously that sunset-ish colors on my monitor make text reading much easier, and cut down on eye strain immensely — particularly for LCD screens. I haven’t tried it on a CRT yet. It sucks for movie watching though. I choose to manually control the F.lux software for this reason. For text reading, I turn my backlight very low, and even more orange than F.lux does, using the monitor’s manual adjustments. (I am using a 32″ HDTV as my monitor while lounging, BTW.)
Also, here are my previous ATI Catalyst color settings for text reading. F.lux overrides these, but in case it’s not your thing:
(gamma, brightness, contrast in that order):
Red: 1.00, 0, 100
Green: 1.10, 0, 80
Blue: 1.00, 5, 36
Not sure about Nvidia graphics cards yet. I’ll post back when I get one in a couple of months.
A few more tips I’ve found helpful:
Peach light bulbs not only help get the blue out, but are wonderful for entertaining guests. Everyone looks better. You can also paint energy-saving flourescent bulbs with non-toxic paint from the craft store. They last for years and they’re luke warm. Try splattering the paint if it ends up too dark when coated. I’ve made “make-up” lighting for my bathroom this way (a.k.a. day (blue & pink,) evening(peach,) office (blue, green, and pink.))
Try using plug-in timers on lamps and/or plant lights to create “F.lux” for your home.
When I get off the computer or TV and read before bed, even with an ebook reader or cell phone, I fall asleep on time and get much better sleep. Admittedly, though, I have my ebook text set to yellow on a brown background. Intersting that!
Lastly, I either use a loud box fan or the White Noise selection at http://www.simplynoise.com/ to drown out noisy neighbors, or just for particularly sleepless nights. The pink noise is great for covering voices. The White noise is nice and reminds me of an airplane ride. The Brown is very nice at first, but strangely this and the pink keep me awake. I’d like to find a grey noise app somewhere.
Oh! you can mix the 3 types of noise at Simplynoise.com too. Just open 3 browser tabs or windows and they’ll play at the same time. I “think” this would work on the new smart phones with Adobe Flash player too. I’ll try it.
Last post. Sorry for hogging the spotlight.
The reason I suggest all of these techy solutions is because I live in a studio apartment where I am always in the same room with my computer. The computer must stay on 24 hours because it’s my DVR, and has shows scheduled to record at all the time. So far, I can’t even sleep without the sound of the computer fans going. But you all have gotten me thinking about trying to work something else out.
I just found an orange “night mode” screen app for Android! Someone here asked about this and I’m so pleased to have found it.
It’s called Chainfire3D. It’s actually a graphics driver which has the “Night mode” setting inside when you open it…. The bad news: You must be rooted, and you must have a very new device — 1Ghz processors only. The good news: It has several screen color options — Salmon, Red, Amber, Green and Blue. And it has a homescreen shortcut just for toggling night mode with one touch. Not only that, but it’s original purpose is to speed up your phone while playing high-end 3D games. I also plan to use the Blue screen mode during the day to see if I feel more awake.
What an excuse to treat yourself to a new gadget! :->
This was my last blue source of light that needed to be eliminated before bedtime. Thanks to all of the advice here I should be able to get on a regular sleep schedule now. Would not have known the value of this app without you all. Thanks again!
What about green light? My alarm clock has green digits.
It’s currently 2:14AM and I’m having trouble sleeping…again. After stumbling across this article I believe some of my sleeping problems are due to my alarm clock which displays the time in bright blue numbers. In the past I had come to believe that I fell asleep faster when facing away from my clock but in the back of my head I didn’t see any reason why this would be, however I guess that suspicion was totally correct!
THANK YOU for the f-lux idea. I’m going to insist my 16yo daughter install on her laptop. She loves her laptop (bought it herself with her own money!) but she uses it ALL THE TIME, and it’s in her room. She has memories of being 3-4 and wondering why everyone else in the house was sleeping but her. These days, she might fall asleep by 3am. Of course, I’ve mentioned Primal/grain-thing to her, but she LOVES her grains too much. But, hopefully, adding this free little doo-dad to her laptop might have a positive effect on her sleeping.
Talk about counterproductive! who knows if this picture is accurate, but the “glow points” in this supposed sleep mask appear to glow blue. Yikes.
http://www.drugstore.com/sound-oasis-glo-to-sleep-sleep-therapy-mask/qxp373631
I enjoyed this article and all the comments and posts. I’ve been basically primal for 4 years but I am SCREWED because I work nights. Always have (tech support, we’re talking the bulk of 20 years) so I cannot implement most of these wonderful suggestions. I’ve studied circadian cycles, shift work, etc., and am doing the best that I can. I have a very dark room, take melatonin before going to bed, take my supplements when I get up, and sleep very well during the day. I think I am one of those nocturnal people who were sent to protect the others during the day because being up at night is so natural for me. Whenever I have to come into work during the day for training, etc., it’s miserable and so hard to stay awake, but I am fully awake all night without caffeine or drugs. But am I *really* an anomoly? While my health (other than asthma/allergies) is close to perfect (you should see my blood counts!) I’ve gained 12 pounds or so this year that will not come off though I have not changed my eating habits, etc. When I’ve written to other primal “gurus” I am dismissed with “quit working nights” like it’s that simple. For one thing, I love the benefits of working nights, not the least of which is the shift differential that goes along with it; after losing a comfortable job I held for 20 years I’m stuck starting over again so I’m making the most of where I’m relegated presently. So am I doomed to never have the best health I could because I am a night owl? Or am I already there (since being a day person is so foreign)? I have even thought about taking a day shift to see if that would help me drop these pounds (I stayed in my 5# range for 3 years) but I can’t afford the pay cut so that’s not an option at this time. I am actively looking for another job and am open to working days though I know my mindset is not ready for it. But my motto is “If you continue to do what you’ve always done, you’ll continue to get what you’ve always gotten” (and yes, I sell that on a t-shirt!) so if I can afford to change shifts, perhaps I will. Thanks for reading.
This is bull crap. I have been sleeping with a light on since I was born, and I don’t ever have a problem. If you condition your body at a young age it will get used to how you sleep, with light or not. Obviously if you sleep with light off the entire time your alive, it would be difficult to get used to light on. For me, I find it extremely difficult to sleep with light off. I constantly wake up. It’s the same effects for people towards light on, just this time, it’s off.