Shedding Some Light on Night Shift in iOS 9.3

Many people are increasingly concerned about the effects on sleep of blue light emitted by smartphones and tablets, particularly since the following publication made headlines last year:

Chang, A.-M., Aeschbach, D., Duffy, J. F., & Czeisler, C. A. (2015). Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proceedings of the National Academy of Sciences, 112(4), 1232–1237.

In 1998, it was discovered that there are blue light receptors in the retina whose purpose is to inform the brain’s circadian mechanisms, including the hormone, melatonin, and the suprachiasmatic nucleus (in the hypothalamus). Light can delay and lessen melatonin levels, increasing sleep onset latency and possibly having other deleterious effects.

Empirical psychologists (should) know that we are still at a relatively early stage of research on this subject. In the study quoted above, for instance, participants in one group read from an iPad® for 4 hours; participants in the other group read from print books. Both groups were exposed to low ambiant light conditions. The researchers’ experimental control makes it easier to identify cause effect relationships, but makes generalization difficult. Blue light is emitted, for instance, from all kinds of devices (TV, etc.), therefore it is also important to compare tablet reading with exposure to other devices. Many people, for instance, have switched from watching TV to using smartphones and tablets; i.e., they have changed one source of blue light for another. It would also be important to compare tablet reading in regular ambiant light conditions with book reading in regular ambient light conditions.

The Chang et al. paper has already led to a little cottage industry of research and development. According to Google Scholar, the 2015 (Chang et al) paper mentioned above has already (as of January 22, 2016) been cited 68 times. While there are several other studies on blue light, it will take scientists quite a while to properly understand the mechanisms involved and how best to manipulate them, considering that there are many sources of light, that circadian mechanisms are complicated, and there are many other variables to consider and manipulate.

Nevertheless, some sleep researchers and health bloggers now suggest that people use blue light filtering lenses at night. Consider this quote from blogger Chris Kresser.

A better option, in my opinion, is to use amber-lensed goggles once the sun has gone down. These blue-blocking lenses are highly effective in reducing the effects of blue light exposure, and in most cases completely eliminate the short-wavelength radiation necessary for nocturnal melatonin suppression. (22, 23, 24) These goggles have been shown to improve sleep quality as well as mood, simply by blocking blue light and simulating physiologic darkness.

That is one approach, but to say it will not appeal to everyone is perhaps an underestimate. (Where’s the research on that?) I can’t help but wonder what Donald Schön’s, author of the influential 1983 book The Reflective Practitioner (discussed in Cognitive Productivity), would have thought of the recommendation. One size does not fit all…

Night Shift in iOS 9.3

In (indirect) response to the dissemination of blue light research, many people have been staying away from their iPads at night, and telling others they should do the same. (We at CogSci Apps Corp. have received emails to this effect, more on this below.)

As illustrated by the Apple Watch, the Health App, Health Kit®, Apple is intent on contributing to its customers’ health. Moreover, presumably, Apple® has sensed an impact of blue light concerns on sales of their apps (and possibly of iOS devices).

So, in iOS 9.3, Apple will release a new version of iOS that has a Blue Light Reduction setting in the Display & Brightness panel. This will shift the color spectrum from blue towards yellow. You will also be able to schedule this setting.

Here is how Apple describes it:

Many studies have shown that exposure to bright blue light in the evening can affect your circadian rhythms and make it harder to fall asleep. Night Shift uses your iOS device’s clock and geolocation to determine when it’s sunset in your location. Then it automatically shifts the colors in your display to the warmer end of the spectrum, making it easier on your eyes. In the morning, it returns the display to its regular settings. Pleasant dreams.

That’s clever!

Light and mySleepButton?

Occasionally, we get emails from customers who wonder about the light emitted by devices on which they use mySleepButton. To these CogSci Apps Corp. responds as follows:

  • There is no research to our knowledge that demonstrates a statistically significant and important effect of briefly looking at your screen to start an app like mySleepButton. One only needs to glance at the screen for two to five seconds to launch and start mySleepButton.
  • In the very unlikely event that briefly looking at a screen can delay sleep onset, this needs to be balanced against the potential benefits of mySleepButton (possibly decreased sleep onset latency, less anxiety about falling asleep, etc.)
  • It is possible to control mySleepButton without even looking at the screen. For example, you can use the headset controls to start, pause and resume play of mySleepButton packs.

Once iOS 9.3 is released, users will also be able to use the Blue Light Reduction setting, though that setting is much more pertinent to apps users stare at for a long time than mySleepButton.

The Need for Light Smart-Homes, Workplaces and Glasses

Night Shift in iOS 9.3 is merely part of the beginning. Unless new discoveries in circadian research suggest new directions, we may be looking at a future of smart artificial environments. From your smartphones, watches and who knows what else, you might be able to control the spectrum of all the light-emitting devices in your home. Under this scenario, society need not shift towards special-purpose glasses.

Having said that, however: who knows? In the future, there might also be smart glasses that can be dynamically configured to filter blue light.

The Big Picture

When trying to improve the quality of their sleep, we recommend users consider a large spectrum of factors. With respect to blue light: they should consider its various sources (TV, etc.). Night Shift is likely quite relevant to users who spend a lot of time on their iOS devices. Similar technology is available for OS X, Windows and other operating systems.

There are good reasons to avoid stressful activities before bed: watching or reading the news, reading or writing emails and messaging, etc. Of course, there are also pleasant, vigorous bed time activities that may be conducive to sleep upon completion.

To complete the picture, check out our sleep tips.

References and Related Readings

Apple (22 January, 2016). iOS 9.3 Preview. Retrieved from on 2016-01-22 .

Beaudoin, L. P. (2015), Cognitive Productivity: Using Knowledge to Become Profoundly Effective. BC: CogZest.

Brainard G. C., et al. (2001) Action spectrum for melatonin regulation in humans: Evidence for a novel circadian photoreceptor. Neuroscience 21(16), 6405–6412.

Chang, A.-M., Aeschbach, D., Duffy, J. F., & Czeisler, C. A. (2015). Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proceedings of the National Academy of Sciences, 112(4), 1232–1237.

Mistlberger, R. E., & Rusack, B. (2005). Biological rhythms and behavior. In J. J. Bolhuis & L.-A. Giraldeau (Eds.), Animal Behavior (pp. 71–96).

Holzman, D. C. (2010). What’s in a color? The unique human health effect of blue light. Environ Health Perspect. Environmental Health Perspectives. 118(1): A22–A27 . Retrieved from

iMore (18 January, 2016). Night Shift in iOS 9.3: Explained!
Kresser, C. (2013). How artificial light is wrecking your sleep, and what to do about it

President, CogSci Apps Corp. Author, Cognitive Productivity

Leave a Reply

Your email address will not be published. Required fields are marked *


This site uses Akismet to reduce spam. Learn how your comment data is processed.