What is blue light and how does it affect sleep?

If you struggle to get enough sleep, you’re not alone. One in five people have difficulty sleeping.¹ 

But have you considered that your smartphone or laptop could be to blame? 

Screens have become an integral part of our daily lives, with Brits spending on average three hours a day on our mobile phones and over three hours on tablets, laptops or desktop computers.²

Yet these handy devices emit blue light which may be powerful enough to stop your body from producing enough melatonin for a good night’s sleep.³  

Understanding blue light and its sources

Unsure if you’re coming across blue light in your day-to-day life? Let’s look at what it is and where it comes from.

Definition and characteristics of blue light

So, what is blue light? Light is made of electromagnetic energy that travels in waves of varying lengths. 

Blue light is a type of visible, high-energy light with a short wavelength, ranging from 400 to 490 nanometers⁴, giving it its blue hue. Around one third of visible light is blue light.⁵ 

Common sources of blue light

The biggest source of blue light is the sun.⁶ 

Blue light is one colour found on the visible light spectrum (can be seen by the human eye) which includes all the colours of the rainbow.⁷ 

Visible light is part of the electromagnetic spectrum, which includes different types of radiation, even those that humans can't see, such as ultraviolet or infrared.⁸ 

All types of visible light can have an effect on our natural sleep-wake cycles, known as our circadian rhythm, however it’s thought that blue light has the biggest effect.⁹ 

Other common sources of blue light include:

• smartphones
• tablets
• computer screens
• televisions
• LED and fluorescent lights

Differences between blue light and other types of light

Blue light has a shorter wavelength and higher energy than many other types of visible light, such as red, orange, yellow and green light.¹⁰ 

Your eyes are also less effective at filtering blue light.¹¹ 

This means more of the light passes through your eye, stimulating the brain and potentially affecting sleep hormones, which is why blue light is thought to have a greater impact on sleep.¹¹

The impact of blue light on sleep patterns

Simply put, blue light may make it harder for you to sleep and disrupt your sleep pattern. Let’s look at why this is such a problem.

How blue light affects the production of melatonin

Melatonin is a hormone produced naturally in your body by the pineal gland in the brain.¹²

When a receptor at the back of the eye detects blue light, it sends a signal to an area of the brain called the hypothalamus,¹³ which regulates body temperature, hormone release, and the circadian rhythm which is linked to sleep.¹⁴ 

The hypothalamus alerts the pineal gland to stop melatonin production so we can stay awake and alert.¹⁴ 

While all types of light can suppress melatonin, blue light is thought to be the most powerful.¹⁴

Disruption of the circadian rhythm by blue light exposure

Your body’s natural circadian clock is an internal 24-hour cycle regulating sleep, wake patterns and other bodily functions.¹⁵ 

It relies on natural blue light during the day and the full spectrum of light to align your body clock.

Blue light has the biggest effect out of all visible light on our circadian clock, letting our brain know that it’s daytime and we should be awake.¹⁶

If our brains detect blue light from digital screens, fluorescent light or LED lighting at night it might make us think it’s still daytime and may continue suppressing melatonin release.⁶,¹⁷

Then, when you close your eyes and try to rest, it’s possible you won’t have produced sufficient melatonin to help you fall asleep. 

Effects of blue light on sleep quality

Blue light exposure during the day can help to improve alertness, brain function, mood and memory, as well as helping keep our circadian body clock in check.¹⁷,¹⁸,¹⁹ 

However, too much blue light at night can have multiple effects on the quality of your sleep.⁹,²⁰

Long-term exposure to blue light at night may lead to:

• negative effects on sleep quality
• reduced sleepiness at night
• taking longer to get to sleep
• altered circadian rhythm (sleep-wake cycle)
• suppression of melatonin at night, which can negatively affect sleep ⁹

Strategies to minimise blue light exposure for better sleep

Luckily, you can do plenty of things to lessen your exposure to blue light at night. Following these tips can help you get better sleep.

Reducing screen time before bed

Reducing your exposure to blue light before bedtime may improve your sleep.⁶

It’s recommended that you avoid looking at bright screens for two to three hours before bed to give your brain time to signal the release of melatonin.⁶

You might find it helpful to set an alarm to remind yourself to put down your devices and do something else before bed, such as reading a book.

Reducing blue light exposure at night

It’s hard to resist the temptation to look at your phone, even if you’re just about to go to bed.

One way to reduce exposure to blue light is to turn off electronics and try using a red or orange light to read or to try using night mode on devices like phones.²¹

You may have heard of blue light glasses that claim to filter out blue light to reduce eye strain and improve sleep. 

However, the jury is still out on just how effective these glasses are.²² 

While further research is required, some reviews of blue-light filtering lenses have been sceptical.²³

Creating a sleep-friendly environment

Changing your sleeping environment can make a huge difference if you struggle to drop off to sleep or stay asleep. 

Below, we’ll go through what to consider when creating a sleep-friendly environment.

• Lighting. Sleeping in a brightly lit room can significantly reduce melatonin production.²⁴ Switching to dim, warm-coloured lights tells your brain it’s time to get ready for bed. 
• Blackout curtains or shades. These help prevent outside light from entering the room and disturbing your sleep. These are particularly helpful if you work at night and sleep during the day.
• Earplugs. Even if you sleep alone, noises from outside or in other parts of the house can disrupt your sleep, so earplugs can help.
• Music. Some people struggle to relax when the room is completely silent. If this is you, try putting on white noise, gentle music or ambient sounds to help you drift off.
• Room temperature. Check the room is a comfortable temperature and well-ventilated before you go to bed.

The final say

Struggling to fall asleep or waking up at night may not seem like a big deal when it's a one-off. 

But frequent nights of disturbed sleep or taking a long time to drift off can significantly impact your daily life, from your mood and memory to your health and wellbeing.²⁵

Fortunately, making a few simple changes can help you drift off into a natural sleep so you feel refreshed and ready to go the next day. 

To find out more ways you can improve your sleep and boost your wellness, download the H&B&Me app to set targeted sleep goals and access expert advice. 

References

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24) Tähkämö L, Partonen T, Pesonen AK. Systematic review of light exposure impact on human circadian rhythm. Chronobiology international [Internet]. 2018 Oct 12;36(2):151–70. Available from: https://www.ncbi.nlm.nih.gov/pubmed/30311830  

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