BLOG: Changes in the blue light conversation – sleep disruption

My last two blogs addressed how the blue light discussion has progressed from fringe to more mainstream, and I covered supplements, lenses, lighting, digital screens and retinal damage.

In continuing the discussion on digital screens, I want to focus on sleep disruption. In a previous blog on good blue light, I discussed that while blue between the wavelengths of 459 nm and 484 nm are essential for daytime alertness through their suppression of melatonin, these same wavelengths are not so good after dark as we need melatonin secretion for sleep.

Protecting sleep

Spectacle lenses, screen shields and apps have all been put forth as a potential way to limit blue light exposure at night to promote better sleep. Recently, Apple released iOS 9.3 with Night Shift, an operating system feature that adjusts the amount of blue light emitted from the device based on the time of day. However, controversy on whether digital device screens emit enough blue light to affect sleep abounds.

On March 23, the day after the release of Night Shift, an article in Forbes quoted a display industry executive: “Night Shift, which turns down the amount of blue light produced by the display, won’t significantly affect the production of melatonin enough to influence the circadian rhythm and improve the user’s nighttime sleep cycle. I’ve looked into this before, and it’s more of a placebo effect.”

He follows with: “This is an effect that I have been following for many years. I am not a sleep researcher, but I am a theoretical physicist with extensive knowledge of the displays, light spectra and human color vision. It is clear that many sleep researchers do not have a very good understanding of displays, light spectra or human color vision, so many of their conclusions regarding displays are simply not correct.”

In mid-February, an article appeared in the U.K.-based journal, Optician, where a researcher states: “Individuals are going to get far more stimulus from their environment or domestic light sources, especially their LEDs. I wouldn’t purchase devices with a spectral filter, as I think this is protection against a nonexistent problem, similar to radiation screens incorporated in early visual display terminals. I think this is totally unnecessary and a gimmick.”

Currently, there are no studies that look at the effects on melatonin secretion by reducing blue light at the source, such as with an app or operating system, or by shielding the eyes with currently available blue filtering spectacle lenses. However, I, as well as many colleagues I have spoken with, have plenty of anecdotal evidence from numerous patients (too many to be a “placebo effect”) that report better sleep when they wear blue light-absorbing lenses when viewing devices in the evening. To be clear, these are lenses with blue light-absorbing pigment in the monomer, which have moderate filtration above 460 nm, not blue light antireflective lenses.

A recent paper by Chang and colleagues looked at the use of light-emitting e-books before bed. Compared to those reading a paper book, the e-book group (they read from an iPad) had reduced evening sleepiness, took longer to fall asleep, had reduced melatonin secretion, had phase delay of their circadian clock and had reduced next-morning alertness. It should be noted that all authors of the Chang paper are on staff at the Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women’s Hospital, as well as the Division of Sleep Medicine, Harvard Medical School. As this study clearly shows that handheld digital devices affect sleep, clinicians should view claims of gimmickry against efforts to reduce blue light emissions from screens with trepidation.

Patient care

This blue light conversation is not going away, and as the story grows in the mainstream media, we will all be faced with questions from our patients asking advice on the use of digital devices at night. In terms of clinical decision-making and recommendations, I think we have all heard the adage to treat patients as we would a family member.

Until definitive studies are available to guide us, I would advise mine to turn down their screen brightness, wear blue-filtering spectacle lenses, try to limit screen time before bed and install an app or operating system upgrade such as Night Shift to reduce blue light at night. What advice would you give to yours?


Challinor S. In Focus: Software casts shadow over blue light lens thinking. Optician. Posted February 15, 2016.

Chang A, et al. PNAS. 2015;112(4):1232-1237. doi: 10.1073/pnas.1418490112

Kelly G. Apple iOS 9.3 has a nasty surprise. Forbes.