Blue light is bad at night. It prevents sleep which in turn increases risk for diabetes, obesity, and other metabolic disorders. I’ve written about this. Here’s yet another study:

Bigger, Brighter, Bluer-better? Current Light-Emitting Devices – Adverse Sleep Properties And Preventative Strategies, Frontiers in Public Health, 13 October 2015

They even tested an old 1st generation Kindle Paperwhite and it had high levels of the short-wavelength, blue-green light that keeps us awake.

Conclusion: The LE devices tested [smartphone, tablet, e-reader] were all bright and characterized by short-wavelength enriched emissions. Since this type of light is likely to cause the most disruption to sleep as it most effectively suppresses melatonin and increases alertness, there needs to be the recognition that at night-time “brighter and bluer” is not synonymous with “better.” Ideally future software design could be better optimized when night-time use is anticipated, and hardware should allow an automatic “bedtime mode” that shifts blue and green light emissions to yellow and red as well as reduce backlight/light intensity.

Astronauts employ this knowledge to regulate their sleep and circadian rhythms. They use blueish lights during their “day” and reddish lights as their “night” approaches. The sun emits short blue wavelengths during the day which inhibits melatonin and keeps us awake and alert. Light therapy for depression works in a similar way. I think we need to pay attention to this.

The BBC covered the study:

Phones Need ‘Bed Mode’ To Protect Sleep, BBC, 15 November 2015

Paul Gringas, the lead author, said:

“There is converging data to say if you are in front of one of these devices at night-time it could prevent you falling asleep by an extra hour.”

“It’s not good enough to say do less and accept this is the world we live in, they’re fun devices but we do need some protection on what they do at night-time.”

What to do?

Harvard Medical School suggest avoiding blue-light 2–3 h before you go to bed, while the National Sleep Foundation suggest turning all electronic devices off at least an hour before bed.

I’m sorry. That’s not going to happen. However, the authors did test orange-tinted glasses which were effective at filtering blue light. And they suggested that filtering software such as f.lux would also be effective.

Let me share my first-person experience. I downloaded f.lux on my laptop. It works. Before f.lux I’d be up for hours. I am now, literally, asleep on my laptop in about 15 minutes. It’s like taking a sleeping pill.

Here’s an example of what your screen would look like, from f.lux’s site. You can try it yourself here.

Without f.lux:

With f.lux: