The Effect of Light on Sleep

Contents

Introduction

With the creation of electricity in the late 19th century came a great number of technological advancements and improvements to our daily life. It did, however, also come with an unintended consequence, the reduction of our quality of sleep. Following on from our ‘How to Light Your Bedroom Guide,‘ we explore how both natural and artificial light effect our sleep.

Fundamentals of Sleep

Our sleep pattern is determined by the circadian clock. This is most sensitive between the period of two hours before bedtime and one hour after usual wake up time. Our usual waking and sleeping cycle is determined by our internal circadian rhythms. These work in a 24 hour cycle. On average, the highest periods of sleepiness during the day are 2am – 6am, 2pm – 5pm and 12am -2am. These rhythms mean that the pressure on the body to sleep will rise the longer a person is awake.

A grown adult needs, on average, 78 hours of good sleep a week. Our ability to sleep is largely determined by the hormone melatonin, which is produced in the brain’s pineal gland. This relaxes muscles, increases drowsiness and causes the body temperature to drop.

During sleep the body goes through various processes. It repairs tissue, fights illness and infection, forms memories from the day, increases mood, recovers muscles and helps children grow. Humans go through four to six sleep cycles throughout the night, each averaging between 70 and 120 minutes. This includes both the deep rapid eye movement sleep (REM) and non-REM sleep.

Light & Sleep Risks

Both while awake and asleep, light enters through the eyes and eyelids where it sends a signal from the back of the retina to the nerves in the brain.

As well as reducing the quality of sleep, exposure to light during sleep has been linked to a variety of health issues. 

It; 

• Disrupts insulin and blood glucose which causes a risk of insulin resistance
• Suppresses the production of melatonin 
• Causes eye strain
• Increases overeating and the likelihood of obesity
• Impairs mental functions due to sleep deprivation
• Reduces the effectiveness of cells that attack viruses and cancer 
• Causes a risk of infection due to decreased antibodies 
• Alters metabolism
• Increases the risk for cancer, cardiovascular problems, illness, accidents, depression and hyperactivity

Light Types

Exposure to natural light during the day synchronises circadian rhythms with the sun’s rise and fall and artificial light increases alertness when near it. Natural light is around 10,000 lux and white or warm yellow in colour. Reduced access to natural light causes mood changes and is part of why seasonal affective disorder (SAD) presents in some people. Therefore finding interior light sources with a CRI and colour temperature similar to daylight will allow circadian rhythms to process more naturally, improving mood, sleep and general health.

Studies have shown that blue light is the type of light most detrimental to sleep quality. Our eyes are highly sensitive to its wavelength and it has been proven to suppress melatonin and circadian rhythms for twice as long as other light types. Electronic devices emit blue light, however some modern devices have a mode that can turn this off.

White light is less sensitive to the eyes. It boosts alertness and mood therefore is recommended for daytime but not nighttime usage.

Yellow and orange light often have warm colour temperatures and low luminance levels. These factors promote relaxation and allow melatonin to process as it naturally should.

Red light is the best kind of light to use to increase sleep quality during nighttime. It is the best kind to use for a night light as it has a long wavelength and has little strain on the eyes.

Top Tips to Improve Your Sleep

The best ways to optimise sleep are to:

• Get blackout curtains as pitch darkness promotes quality sleep
• Use red night lights
• Install dimmers in bedroom lights
• Reduce technology use and avoid screen time one hour before bed
• Install bulbs that have a warmer colour temperature and softer lumens level
• Use a sleep mask to block light from entering your eyes
• Expose yourself to bright, natural light during the day where possible to allow synchronisation of circadian rhythms

Conclusion:

Light and sleep are intrinsically linked. In a world with an abundance of artificial light it is important to buy products that will protect your health. If you want to learn more about sleep safe lighting, speak to a member of our team or call into our showroom for a free consultation.