Blue light at night? Maybe it influences the quality of your sleep

Human eyes are by design very sensitive to light. They sense and react to light in the environment without us even knowing, by dilating or contracting pupils to control light input. However, of all the light that the sun emits, humans can only see one portion of it. This is known as visible light, and its spectrum gives us the colours of the rainbow.

These sections, or wavelengths, vary in shape. Waves from the red side of the spectrum are bigger than the blue side, but blue light has a higher frequency. Our exposure to blue light has increased over the last fifty years due to the introduction of screens and artificial lighting, and things like energy saving lightbulbs particularly contribute to the problem.

An abundance of blue light can be a problem because of the way it influences our brain activity. During daylight hours, we are supposed to feel active and energetic thanks to our circadian rhythm, which is influenced by daylight and tells us when to sleep and when to be awake. However, blue light from screens and artificial lighting mimic daylight and trick the brain into believing it’s still day, regardless of the hour.

This hinders the production of the hormone melatonin, which regulates your wake and sleep cycle. Devices such as tablets, computers, and televisions can therefore be counter-productive if used in an effort to fall asleep as the brain is left feeling more awake.

According to a recent study published in the Proceedings of the National Academy of Sciences, by the University of Texas, using such devices only a few hours before sleeping will disrupt your REM sleep (dream sleep), and will decrease your attentiveness the next morning.

Not only can your sleep be affected by late night exposure to blue light, but other aspects of your health may be at risk too. Harvard researchers placed ten subjects on a routine that shifted their circadian rhythms gradually over time.

They found that blood sugar levels increased, risking diabetes, and the amount of leptin (a hormone that leaves you feeling full after eating) decreased, which could be an indicator of an obesity risk. Lack of sleep has also been linked to a heightened risk of depression.

The best way to avoid these complications is to reduce the use electronic devices before you sleep. Reading a book before bed with an orange or red light, or even a candle, rather than white light can also help to encourage sleep.

Researchers at the University of Toronto found that those who wore blue-light-blocking goggles in brightly lit conditions had similar melatonin levels to people exposed to dim light without goggles, indicating another form of protection against blue light.

Learn more about the effects of blue light and ways to protect your eyes from long-term eye damage.