Block Those Blues!  Why Blocking Blue Light at night is Important.

Blue Light is part of the spectrum of light that comes from the suns rays.

The bright blue colour of the sky is cued in to our brain and nervous system in such a way that, when we first see it in the morning, it signals our ‘coffee hormone’ called cortisol to be released. When this happens cortisol levels in our body spike as a way to get us up and ready for our day.

Blue light’s effect on Attention and Cognitive Performance

Blue light exposure has been shown to enhance cognitive performance as well as our ability to do tasks that require sustained attention.[1] This is excellent in the morning when we need to feel awake, however, our device screens (televisions, computers, iPads/tablets, smart phones) also emit blue light and can, in this way, have a profound effect on our physiology. If you are going online first thing in the morning blue light exposure is not such a problem, however, if you are surfing the web just before going to bed, your body is getting a mixed message. The blue light is telling our body to wake up, and it can impact the quality and quantity of your sleep.[2]

Blue light’s effect on Melatonin

Blue light profoundly affects circadian rhythm, which is our daily sleep/wake cycle. It does so by changing the timing and rate of the secretion of a hormone called melatonin from our brain. Melatonin is the sleepy hormone, it’s the one that prepares our body to slow down, rest, and fall asleep. Much of the healing that is done in our tissues occurs at night. Immune function is optimized during sleep. This is why proper deep sleep is critical for disease prevention.[3] There is a strong link established between a variety of diseases and a disruption of circadian rhythm. These include: breast, prostate, and colorectal cancer, as well as obesity, diabetes and depression.[4] Breast cancer has a particularly strong correlation with light at night even to the extent that it is considered an occupational hazard for female shift workers in some countries.

Other sources of blue light

Apart from our device screens, we are exposed to light at night from street and building lighting. Even when this light does not contain blue light, it can still disrupt our circadian rhythm. This is why it is also important to ensure that our bedrooms are dark while we are sleeping. Most curtains allow light to come in to the bedroom even while drawn closed and so black out blinds are often the best way to ensure complete darkness in the bedroom. When assessing an appropriate level of light while sleeping, you can do the following: turn off the lights, draw the curtains/blinds and wait in the room for ten minutes or so to allow you eyes to adjust. In a bedroom that is optimally dark, you should not be able to see your hand in front of your face.

Is there a ‘life hack’ for this?

You don’t necessarily have to avoid using your computer etc before bed. There is a great feature for your desktop called ‘F.lux’. It is a freely downloadable program that modifies the type of light that your device screen emits from white/blue light to what is called ‘melanopic’ light.   This type of light has an orangey colour that seems a bit strange when you first see it on the screen, but quickly starts to seem normal as you get used to it. Melanopic light does not serve as a strong cue for your body to release cortisol, and does not strongly impact circadian rhythm. You can also use ‘Night Shift Mode’ on your iPhone, or wear blue light blocking glasses (available at Empower Health). Every one wants to get the most out of their sleep time, and to feel as refreshed as possible in the morning.

This is where ‘sleep hygiene’ comes in. Brushing your teeth before bed is an oral hygiene practice. Avoiding blue light after the sun has gone down is a key aspect of good sleep hygiene practice and it will pay dividends in terms of helping you get the rest that you need to feel vital during the day!


[1] Sarah Laxhmi Chellappa,et. al.  Non-Visual Effects of Light on Melatonin, Alertness and Cognitive Performance: Can Blue-Enriched Light Keep Us Alert? PLoS One. 2011; 6(1)

[2] Laura K. Fonken et. Al. Illuminating the deleterious effects of light at night. F1000 Med Rep. 2011; 3: 18.

[3] Martin Aube et. Al. Evaluating Potential Spectral Impacts of Various Artificial Lights on Melatonin Suppression, Photosynthesis, and Star Visibility.  PLoS One. 2013; 8(7)

[4] David C. Holzman.  What’s in a Color? The Unique Human Health Effects of Blue Light.  Environ Health Perspect. 2010 Jan; 118(1), and Martin Aube et. Al. Evaluating Potential Spectral Impacts of Various Artificial Lights on Melatonin Suppression, Photosynthesis, and Star Visibility.  PLoS One. 2013; 8(7)