Does blue light exposure really impact our sleep? This is what a top sleep scientist wants you to know

We don’t go to bed with the sun anymore – it’s been a long time since that’s been a realistic thing for humans. We are bathed in artificial light, often right up until we go to sleep. 

It’s a common piece of advice from sleep experts that you should start to knock down the decibel level of your light exposure a couple of hours before bed. You’ve also probably heard a lot of advice to limit television, computer, and smartphone use before bed, because of the type of light these devices emit: blue light. 

Blue light, which has a shorter wavelength, has more of an impact on circadian processes. Research shows that it can suppress the production of melatonin like sunlight does. So basically, you can think about it this way: if you’re gazing into your phone at night, whether you’re working on an email or relaxing by watching a show, it’s a bit like gazing into a beam of sunlight. The message your brain’s getting is, Wake up!

“You don’t have to sit in a pitch-black room listening to ocean sounds to prepare your brain and body to fall asleep.”

If you Google “sleep hygiene,” you’ll find a million articles telling you not to have any blue light exposure two hours before bed: no TV, no phone, no computer. And look – they’re not wrong. Melatonin is a significant player in the onset of sleep, so you do want to be aware of that and limit your light exposure to the extent that you can. But this isn’t an all-or-nothing situation. You don’t have to sit in a pitch-black room listening to ocean sounds to prepare your brain and body to fall asleep. Limiting light exposure in the lead-up to bedtime is a good idea. It’s one of the many levers you adjust and move to a setting that works for you. But I’m of the opinion that the blue-light exposure alone is not going to make or break your sleep success.

From where I sit, of all the things that impact people’s sleep, the blue-light issue is probably a fairly minor one for most peo- ple. The industry that’s cropped up around limiting blue light to preserve the melatonin system might be bigger than the ac- tual problem. I went to my ophthalmologist recently and they wanted to put a purple tint on my lenses: “It’s blue-light block- ing, it’ll help you sleep better!” they said. I said no, thanks. And they did it anyway.

I’m a sleep scientist – I know exactly what’s happening when I lie in bed in the dark, scrolling through Twitter, and yet I still do it. I’m just as susceptible as anyone to the stimulus-reward loop of social media and phone apps. Sometimes what you’re doing on your blue-light emitting device is actually relaxing – I always tell people it’s OK to watch TV at night, for example. 

Sleep-advice websites tend to take a hard line on this and say “no screens,” but look: not everybody is going to find relief from sitting in a chair and meditating. For some, that kind of thing amps up their anxiety when they become more aware of upsetting thoughts. Maybe what they really need is to softly zone out to reruns of The Office or Sex and the City (or whatever floats your boat). But a lot of the other stuff we do on our laptops, tablets, and phones do become way more of a problem – but it’s not solely because of the blue light. It’s that we become too engaged in them. The reward system in your brain is activated by the design of social media apps. And what it wants most is . . . more.

That’s what’s keeping you awake. The light isn’t helping, to be sure. But even if you get the purple tint on your glasses, if you’re reading one stressful news story after another on your laptop before bed, you’re still not going to be able to fall asleep. A blue-light filter isn’t a magic bullet. The recommendation to disengage from your phone and other devices is an important one – but let’s be clear about the reason. We can’t engage in content that’s going to get our nervous system fired up, no matter what type of light filter we use. It’s not the light you need to turn off – it’s the engagement.

Extracted from The Seven-Day Sleep Prescription by Dr Aric Prather is available now (Penguin Life, £9.99).