Blue Light and Poor Sleep

Using your smartphone and watching television before bedtime can keep you awake by stimulating your brain with blue light.

It is scientifically proven that blue light from electronic devices interrupts the secretion and production of the sleep hormone melatonin.

Melatonin is the hormone responsible for signalling your brain that it is time for sleep, so interrupted secretion can keep you awake.

Melatonin and blue light

Harvard researchers studying blue light found that blue light suppressed melatonin for twice as long as the green light and shifted circadian rhythms by twice as much (3 hours vs. 1.5 hours) – in other words, it is twice as detrimental to sleep.

This study from 2014 also found that people using a blue-light-emitting iPad before bed started producing melatonin 1.5 hours later than usual the next day.

In our article about melatonin and sleep, we mentioned blue light as one of the triggers for melatonin deficiency. The science backs this up; healthy people exposed to blue light for extended periods have less melatonin.

Low melatonin equals disrupted circadian rhythms and sleep cycles. Without a chemical trigger – melatonin to tell your brain it is time for sleep – you will struggle to fall asleep and have a higher chance of waking up prematurely.

Blue light and insomnia

The link between blue light and sleep suppression is well-established, but what about the link between blue light and insomnia?

Because blue light suppresses the release of melatonin, it's widely agreed that it can trigger insomnia and exasperate chronic insomnia.

Spending too much time on electronic devices – smartphones, tablets, laptops, etc. – can also increase anxiety/stress levels, contributing to sleeplessness.

As we discussed in our anxiety and sleep article, anxiety/stress triggers the release of cortisol, the stress hormone. Cortisol reduces the secretion of melatonin and increases the level of adrenaline in the blood, which can keep you awake.

Here's what the cycle looks like:

• Blue light from electronic devices suppresses the melatonin that makes you sleepy, making it harder for you to fall asleep.
• The anxiety/stress from using electronic devices increases the secretion of the stress hormone cortisol, which reduces melatonin secretion even further.

Simply put – blue light and electronic devices are bad for sleep. However, you can do a few things to limit your exposure.

How to reduce exposure to blue light

• Blue light filters – most smartphones and tablets have a blue light filter under the display settings (these are sometimes called night mode). Otherwise, you can download an app that filters blue light.
• Night Light and Night Shift – Windows PCs have Night Light to reduce blue light, while the Mac has Night Shift. Both settings let you schedule the blue light filter, or you can set it to stay on indefinitely.
• Warm colour modes – televisions and monitors let you switch between warm and cool colour picture modes. A warm colour mode will filter out blue light – select the warmest setting when watching TV at night.
• Blue light glasses – you can buy clear blue light glasses to wear during the day or specify a blue light filter for prescription glasses. We recommend wearing these if you sit in front of a computer all day.
• Have strict device ''off'' times – it's good practice to turn your smartphone off an hour before bedtime and your TV half an hour before bedtime. This will give you a break from the screen and reduce your exposure to blue light. Try reading a book, or close your eyes and meditate for a little while.

Summing up

Blue light adversely impacts sleep quality and duration by interrupting the secretion of the sleep hormone melatonin.

Over time, blue light affects our circadian rhythms (body clock), and we can fall into a cycle of being unable to sleep when needed.

Additionally, electronic devices – the most significant source of blue light – can fuel anxiety/stress, triggering the release of the stress hormone cortisol, which suppresses melatonin further – a double-whammy that keeps you awake.