For years now, across multiple posts here on Mark’s Daily Apple, nighttime blue light has gotten a pretty bad rap. Although I’ve mentioned that blue light  during the day is important (and natural sunlight is helpful), I haven’t focused on it, mostly homing in on the circadian-disrupting, sleep-inhibiting, melatonin-blunting effects. As a result, many of you may be entirely unaware of the potential positive, beneficial applications of blue light. Recent and not-so-recent research has confirmed that blue light can actually improve our cognitive abilities, including memory, alertness, reaction time, and executive function – at least in the short term. Oh, and it doesn’t always ruin our sleep. It might even improve it if you expose yourself at the right time.
Wait a minute – blue light is good for us? Sisson, you just got done spending the last few years telling me to excise blue light from my vicinity at night if I wanted a good night’s sleep , and now you’re saying we might actually need more blue light. What gives?
Easy. Context is everything. Blue light at night can have a negative, inhibitory effect on our sleep  onset and sleep quality because it signifies daytime to our suprachiasmatic nucleus, that region of the hypothalamus that sits near the optic nerves and regulates our circadian rhythm according to the light we perceive. But during the day – you know, when blue light naturally bounces around the atmosphere into our eyes – it’s beneficial because presence of blue light matches up with our bodies expectations. Blue light isn’t “bad,” in other words. It’s bad in the wrong context. In the right context, which is daytime, blue light promotes restful, satisfying nighttime sleep .
And for the exact same reasons blue light is bad for melatonin secretion and sleep physiology when we’re exposed at night, it also provides a boost to cognition. The bulk of the blue light research may focus on its inhibitory effects on melatonin and sleep, but a growing body of study is realizing that those same inhibitory effects seen at night can be used to improve alertness, executive function, memory, and other aspects of cognition. What’s negative at night when you’re trying to sleep is helpful or even essential when you’re trying to get work done. Blue light may very well be better than (or at least equal to) caffeine .
Let’s look at a few recent studies to see how we might use blue light to our advantage.
- In this 2011 study , LED backlit computer screens enhanced cognitive function to a greater extent than non-LED backlit screens. Sustained attention, working memory, and subjects’ ability to learn words were all enhanced in the LED group. Both screen types emitted light of the same wavelength, but the LED screens’ light was over twice as intense.
- A recent study (PDF ) compared the effects of caffeine and blue light on psychomotor function (the interface between cognition and physical movement) and found them both to be positive but distinct from one another. Subjects exposed to blue light performed best on tests of executive function that included a distraction ; the same distraction proved too distracting for caffeine users, who fared more poorly. Both groups performed well at a Go/No-Go test , which assesses sustained attention.
- Even visually-blind people with “non-image-forming photoreception” (the ability to sense light) derive cognitive benefits from blue light exposure, according to a recent, very cool study . fMRI tests confirmed that brief exposure to blue light “triggered the recruitment of supplemental prefrontal and thalamic brain regions involved in alertness and cognition regulation.”
- Still, the best way to get your blue light is probably through natural daylight. A 2011 study (PDF ) out of Switzerland compared the cognitive effects of daytime natural light and daytime polychromatic (which includes blue) artificial light. Subjects were exposed to six hours of either light source from noon onwards and subjected to a test measuring executive control. The natural light group was more accurate and made fewer errors. Melatonin secretion were similar in both groups even though the natural light group was more alert.
- Cognition-enhancing blue light during the day also has the likely effect of improving sleep at night. In 2008 , researchers improved alertness and productivity in office workers by switching out their standard fluorescent white overhead lights for blue-enriched white lights. Blue-exposed workers performed better, which was expected, but they also slept better at night (which undoubtedly helped performance).
Not bad, eh? Makes a guy want to step outside and get some fresh air. Or, barring that, stare straight into an LED bulb.
Things to keep in mind when applying these results to your workday:
- Use an LED. Most of the studies used basic LED lights. Others may work, but we know LEDs work. The caffeine/blue light study used a 3-watt, 470 nm, 40 lux RGB LED bulb, similar to this $2 one from eBay . This is another option .
- Or download a blue light therapy app for your smartphone. iOS has Blue Light Therapy  and Android has Blue Sleep Therapy . Turn the brightness up.
- It doesn’t take much exposure to get an effect. Although the caffeine study used hour-long light exposure  times to match the known duration of effect of caffeine in the body, other research has shown changes to brain function with just 50 seconds of blue light exposure .
- Get blue light freely during the day. We’re supposed to get lots of blue light during the day (natural daylight is filthy with it), and the research is pretty unequivocal: blue light exposure enhances cognition and alertness during the day. Ideally, we’d get it from working outside , but artificial blue lighting works too (that’s what they use in the studies). Don’t worry about any negative effects, because there shouldn’t be any (unless you’re a shift worker trying to get some sleep).
- Residual effects on sleep may linger, so time your exposure accordingly. In the natural light study, subjects were exposed through 6 PM and alertness persisted after dark.
- Use it judiciously at night. Up against a deadline or driving late at night? Turn off the f.lux  and hit yourself with the full dose of blue light. Browsing forums and checking email? Don the blue-blocking goggles  and avoid it. Since it’s still going to disrupt your circadian physiology, only use the blue light at night if you really have to.
- You may not notice anything new if you work on a computer with an LED display since you’re already getting a fairly steady dose of blue light from the screen. One way to test this is to use your computer (without f.lux  or goggles) at night. If your sleep is disrupted or you get sleepy later than usual, it’s likely boosting alertness when you use it during the day.
- Don’t ditch the coffee, necessarily. Coffee and blue light can have synergistic effects on cognition and mood . Plus, coffee is delicious.
So, in the end, blue light isn’t a villain. It’s just misunderstood (and misapplied).
How are you going to use blue light to your advantage? Or are you already doing so?
Thanks for reading, folks. See you next time.