Blue light exposure can help you beat fatigue on winter mornings

Spread the love

There’s nothing like waking up to find it’s still pitch dark outside to make you want to crawl back into bed for another hour. That’s why many of us, once November swings round, unpack our wake-up lamps. 

Pre-pandemic, I used to leave the house every day at 5.45am so I could make it to an early gym class and still get to my desk just before 8am. Curiously enough, I was less tired in the morning than I am now, when I often wake up 90 minutes later. Why? I’m sure it’s because I used to use a Lumie wake-up lamp.

It lived on my bedside table, less than an arm’s length away. Despite the alarm going off at 5am, I’d be wide awake and reading the paper by 4.50am. And, crucially, I used to stay alert all day. Today, I sleep better for longer, but I also struggle to snap out of sleep inertia (the period between being properly asleep and seriously awake). Even if I do put the bedside lamp on the moment my alarm goes off, I don’t feel as awake as when I used a specific wake-up light. Why is that?

Why do we struggle to wake up on dark mornings?

First off, it’s worth recapping what happens when we wake up. We’ve got millions of light-sensitive cells in our eyes, and those receptors communicate with the brain about light and dark levels (the light-dark cycle). On receiving light information, the brain and hypothalamus then start to release neurohormones that connect to the body’s individual internal clocks.

During spring and summer, our circadian network is aligned with the light-dark cycle, but when the days start getting dramatically shorter, our internal clocks stop aligning with these external factors – and that’s when we get caught in this hazy no-man’s land of fatigue. 

Woman lying in the dark with light
If you don’t have enough blue light hitting your eyes, it’s going to be harder to feel awake.

What is lux?

On a recent episode of the Radio 4’s Sliced Bread, presenter Greg Foot asked experts to explain how wake-up lights work, and it was revealed that it’s all to do with lux, which is the measure of light intensity in a given area as perceived by the eye. While the number one way to wake the body up is to get out into bright sunlight, the experts acknowledged that it can be difficult to get enough lux during winter, which in turn makes it difficult for the brain to realise that it’s time to get going. And light boxes and wake-up lights work to provide an alternative when you can’t get enough lux from the sun.

According to Penn Medicine News, a person needs at least 30 minutes at 1,000 lux to start the circadian process. This is reasonably easy to by getting outside – on a bright, sunny day, even in the UK, we might get up to 100,000 lux outdoors. Sitting by a window might provide around 3,000 lux, but that can drop to as little as 200 lux if we’re looking at the window from the middle of a room. In short: the more lux, the better able you are to reset your internal clock.

What’s the difference between SAD lamps and wake-up lights?

SAD lamps and wake-up lights aren’t the same thing. The former tend to be much brighter, and you use them slightly differently. A wake-up light is supposed to gently pull you out of sleep by gradually increasing the light in your room; you use an SAD lamp to bathe your face in very bright light – sometimes for up to an hour. The bestselling Lumie Vitamin L lamp provides 10,000 lux at a 20cm distance (using it at arm’s length is the recommended advice).

Your wake-up light, however, could be anywhere in your room, and if it’s on your desk or over on the other side of the room to your bed, you might only be receiving about 400 lux.  

But Dr Victoria Revell, senior lecturer in translational sleep and circadian physiology at Surrey University and scientific advisor at Lumie, tells Foot that you don’t necessarily need to be bathed in the light of a wake-up lamp to feel its benefits.

How do wake-up lamps work?

It’s all about melanopic lux

The point of a wake-up lamp is to reduce sleep inertia, and they do that not just by increasing the brightness of your room, but by changing the levels of certain colours within the light. For the circadian rhythm, you want to be tracking how much light the blue light sensitive photoreceptor – the melanopsin – is getting. 

Melanopsin is the main photopigment that’s responsible for driving the effects of light on your body clock, and you can tell how that’s working by measuring the melanopic lux – the blue light content of the light. The recommendations say you need to have least 250 melanopic lux to feel any effect. 

Much of the current lux guidance is out of date

“The 10,000 lux guidance [as provided by the Lumie amp] is from 20-30 years ago, when people were looking at using light for depression,” Dr Revell explains. “As our understanding of the photoreceptive system has advanced, now we know that if we target those melanopsin photopigments, we can bring down [the light] intensity because we’re giving more blue light.” 

In other words, because of the blue light content, we can afford to have a slightly dimmer light. If you don’t have a plug right by your bed, that’s good news, although the starkest impact is still going to be felt if you can place your lamp on a bedside table.  

Why getting outdoors is still the best way to wake up

Once you are up and awake, your next best option is to get outdoors as soon as possible – even if it’s a cloudy day. There’s so much to get from being outside, whatever the weather. According to Dr Andrew Huberman, tenured professor of neurobiology and ophthalmology at Stanford University School of Medicine, getting outdoors as soon as you wake up can determine your energy levels, sleep cycle and overall health for the rest of the day. 

He’s previously explained that when we wake up, we have a cortisol spike – and when that spike happens, you want to ride the wave. Bringing that cortisol wave earlier in your day has positive benefits, he maintains. For those of us who wake up at a time when light is still low (or on the days you face grey skies), “you probably are not getting enough sunlight in order to set [that cortisol release], so it will take longer… Anywhere from two to 10 minutes of sunlight exposure is going to work well for most people.”

Dr Huberman recommends downloading the app Light Meter, which measures the photon energy in your environment. You should be aiming for anywhere between 10,000 to 50,000 lux for the best cortisol spike, he says.