You may have heard about avoiding bright lights before bed. While this is good advice, it turns out that the choice of bedroom lighting is important because the colours of certain light may disrupt your sleep more than others.

If you have insomnia, you may wonder how bright or dark your bedroom should be for optimal sleep? When should you turn the lights off?

Well, the bedroom should be completely dark. If external light comes in through the window, black-out curtains may help. However, light from the window or your phone can interrupt sleep significantly.

How does Bedroom Lighting Affect Sleep?

Light Levels and Wavelengths

Light plays a central role in regulating circadian rhythm, the body’s internal clock signals when to be awake and when to rest. Light also heavily affects the production of melatonin, a hormone that provides your body’s internal biological signal of darkness. Specialized photoreceptors in your eyes send information back to your brain and influence your production of melatonin.

Many lighting characteristics can be imperative for sleep. For example, higher light levels, measured in lux (a unit of light intensity), have been shown to suppress melatonin.

Light wavelengths have also been proven to be necessary. Shorter wavelengths (the colour blue) can suppress melatonin, and longer wavelengths (the colour red) may not affect melatonin. LED lights may be more energy-efficient, but they tend to produce more blue light. Using dim or red lights before bedtime may help you sleep better.


Worst Colours for Bedtime

It’s well-known that exposure to blue light can disrupt your sleep and negatively affect your sleep quality. LED lights, fluorescent lights and electronic screens all contain blue light.

Studies have shown that green light can also hinder your ability to fall asleep and impact sleep quality. In addition, the same study found that violet light could have a similar effect as blue light.


Red Light Therapy Theory

It is thought that colours closer to red on the light spectrum might stimulate melatonin production. However, more research is needed to support this theory at this time.

A small study examined the effect of 30 minutes of nighttime red light therapy in a group of 20 Chinese female basketball players. The researchers found that after 14 days, participants who received red light therapy improved melatonin levels significantly and their sleep quality, compared to the others not exposed to light therapy.

Most other studies relating to colours that may help your sleep have been performed on rodents. But because rodents are nocturnal and colour-blind, it’s hard to make conclusions from these studies. So, although there is little evidence that red light may induce sleepiness, more human research is needed to back this theory.


Is It Best to Sleep in Pitch Darkness?

In the absence of light, the brain sends a signal to the body, indicating that it is time to rest. As a rule, it is best to sleep in as much darkness as possible. Pitch darkness minimizes distractions and disruptions to sleep.

In addition to sleep quality, here are some other important reasons why it’s best to sleep in pure darkness:

  • Eye strain. Even low levels of light during sleep have been associated with eye strain or discomfort in the eyes.
  • Cancer risk: One study found an association between people whose homes had high levels of artificial light at night and their risk of breast and prostate cancer. However, more research is needed to prove this correlation.
  • Weight gain: Keeping lights on during sleep can affect circadian regulation of metabolism, increasing the risk of weight gain.

The Takeaway

Light is an important external factor affecting sleep. We know that blue light can have a negative impact on your melatonin hormone levels. Exposure to green and violet light could also affect your sleep quality and quantity.

To help maintain your natural sleep cycle, avoid direct bright light exposure before bed. There is no specific time to turn the lights out as everyone has their internal biological clock. However, it’s usually a good signal to turn the lights out and go to bed when you feel sleepy.


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Written by: Melissa Ureten


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