Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
4 Mar

How Light Affects Our Sleep

Blue Light ComputerMost 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.

You want comments? We got comments:

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  1. 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

    Linda DeFever wrote on September 28th, 2010
  2. I know some people that cannot sleep under any amount of light even if it is very little.

    Arlein wrote on October 10th, 2010
  3. 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?

    Boden wrote on October 14th, 2010
  4. Well, I don’t know what to believe anymore, all the experts are saying something different.

    Amanda wrote on October 16th, 2010
  5. “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.

    Duches wrote on October 18th, 2010
  6. Hi

    Is there an equivalent to f.lux for the iphone ?

    Great post btw.

    Onge wrote on November 1st, 2010
  7. 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.

    JoelG wrote on December 6th, 2010
  8. 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!

    susan wrote on December 26th, 2010
    • 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.

      Jonathan wrote on December 27th, 2010
  9. 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.

    wisconsin auto loans wrote on February 23rd, 2011
  10. On the topic of sleep, check out this new piece in the Harvard Business Review – Sleep is More Important than food:

    Anne wrote on March 6th, 2011
  11. 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.

    Raven_Glance wrote on March 14th, 2011
  12. Does anybody know an app for iphone that could do the same as F.lux?

    Omar wrote on May 13th, 2011
  13. 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!!

    Janice wrote on May 25th, 2011
  14. 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?

    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.

    gggirlgeek wrote on June 10th, 2011
  15. 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.

    gggirlgeek wrote on June 10th, 2011
  16. 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 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.

    gggirlgeek wrote on June 10th, 2011
  17. Oh! you can mix the 3 types of noise at 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.

    gggirlgeek wrote on June 10th, 2011
  18. 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.

    gggirlgeek wrote on June 10th, 2011
  19. 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!

    gggirlgeek wrote on June 14th, 2011
  20. What about green light? My alarm clock has green digits.

    Sue wrote on June 27th, 2011
  21. 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!

    Taylor wrote on July 31st, 2011
  22. 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.

    kimelah wrote on October 3rd, 2011

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