Does Your Phone's Blue Light Dimmer Really Work? Let's Ask Science

(ominous music)

As you might have noticed, I am ready for bed.

I've got my jam-jams, I've got my herbal tea, AKA whiskey,

and I've got my fancy computer phone,

which actually dims its blue light

at a certain time each night.

That's because you might have heard

the blue light disrupts your sleep by making you more alert.

And that's true.

Expose humans to more blue light,

even during the day, and they grow more alert.

And it's certainly bad to look

at the raw white light from a phone at night.

But here's the problem: no study has definitively concluded

that this blue-depleted light helps you sleep any better,

meaning the nightcap works, but we still need more studies

on how blue light affects sleep.

So first off, why blue?

Well, no one is quite sure,

but it might be an evolutionary throwback to early mammals,

which emerged at dawn and dusk to forage.

At these times, there's very little blue in the sky.

So our ancestors might have needed

to be more sensitive to this color to see properly.

But this is very much speculation.

What science does know is that

the retina is made up of rods and cones.

You learned this in grade school.

Rods are good for low light and cones are good for color.

But we also have a third kind of photoreceptor called,

deep breath, an intrinsically photosensitive

retinal ganglion cell.

These are sensitive to blue light

and hook up to the circadian system

to regulate sleep and alertness.

So, if you lose your rods and cones,

you can still be affected by blue light.

Now, scientists have done studies looking at

how blue-depleted light affects humans,

but they were hitting them with way more light

than you would get in your typical bedroom,

like 30 times the amount.

Researchers have also looked at the effects

of blue-depleted light on subjects in dimmer settings,

but only for a single night.

Probably not long enough to really see the impact,

but it does suggest that blue-depleted light

has an effect on sleep.

So at the moment, no one can say that getting rid

of a screen's blue light is less disruptive for your sleep.

Researchers need to study more subjects.

They need to observe them over more consecutive nights.

Not only that, but depending on the duration

and intensity of light exposure,

sometimes green can have a more powerful effect

on alertness than blue, which means we might have

more than one color to worry about.

Good news is, until somebody figures out

what's going on here, it's not like dimming

the blue on your phone is going to kill you.

Nope.

Drinking too much herbal tea

and passing out near a candle will do that.