The Dark Side of Blue Light

How your phone, computer and fluorescent lights might be keeping you up at night.

Humans are a species that have adapted to be diurnal, which means active during the light of day and restful at night. This is in contrast to the some of the creatures that might make noise running around at night such as rats and possums, who are nocturnal. At yet despite the fact that we have evolved to sleep at night and be awake and alert during the day, many of us complain of not being able to get to sleep or stay asleep at night, which leads to drowsiness, low productivity and lack of function in the daytime…along with some even more serious consequences.

Circadian Rhythms

But how is that our bodies know to be alert during the day and sleep at night? We can thank the connectedness of our eyes, our brain and the hormone melatonin for that action. When light is filtering through the eyes during the daytime melatonin levels stay low and this helps us to stay awake during the daytime. As the sun starts to set and light levels fall, the eyes detect this decreasing level of light and send a message to the brain to release melatonin. This encourages us to get sleepy, and be able to effectively fall asleep and stay asleep when it’s night time. The whole process of how we fall asleep or stay awake over a 24 hour period is called our circadian rhythm.

Some of us know all too well the effects of light on our sleep patterns, because we struggle to get to sleep or stay asleep when light is filtering into the bedroom, or we find ourselves waking up with the sun. However, we no longer rely on just the sun alone for our light sources these days. Now we not only have light globes, but we also have fluorescent lamps, energy efficient bulbs, computers, phones and televisions that contribute to the light entering our eyes even after the sun has set outside. What is the effect of this?

Light and Sleep

Any light entering our eyes will affect our sleep cycle to some degree. But science has shown that light which is a blue colour has the strongest potential to change our circadian rhythms and alter our sleep cycle. Unfortunately for us, the light in a lot of our light bulbs and in most of our electronic devices is in the white­blue colour range, posing a significant impact to our sleep cycle. You may think there’s nothing to worry about because you turn these lights and devices off when you go to sleep, but the fact is they are affecting your melatonin levels at least 2 or 3 hours before you go to sleep – keeping you up at night even after you’ve switched off the light.

This kind of disruption to the circadian rhythm and sleep cycle can cause much more serious effects than just a sleepless night. Numerous studies have shown that light at night causing an upset in circadian rhythms can increase the risk of cancer, diabetes, heart disease, obesity and depression. These negative risk factors are even more extreme in those who really go against the flow of the circadian rhythm by working nightshift. There is a lot of evidence that exposure to bright lights at night, especially blue colour light, really has a detrimental effect on our health.

Blue Light: Sources and Management

So what are the sources of blue colour light? The obvious ones may be fluorescent bulbs or energy saving lights that emit a blue tinged light. A good way to provide a healthier source of light for night time is to find a red coloured bulb, or at least a warmer coloured bulb, choose a low wattage, and use a red or orange lampshade to offset the blue colours in the light. Red light has been shown to have the lowest effect on circadian rhythms of all light colours.

Of course the greatest source of light entering our eyes at night is often from handheld devices such as phones or tablets, or screens such as the computer or television screen. This is a really significant and unacknowledged source of light that can have major detrimental effects on your health. Turn the phones, tablets and screens off 2­3 hours before bedtime, and switch to a real book or some meditation for relaxation time before bed.

By targeting the sources of light that harm your sleep at night, you can enjoy a better night’s rest and the rejuvenating effects of a good sleep, as well as better health and vitality.


  • Holzman DC. What’s in a Color? The Unique Human Health Effects of Blue Light. Environmental Health Perspectives. 2010;118(1):A22­A27.