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Negative Effects of Blue Light on Sleep

Preparing for sleep with the correct lighting

While blue light can have positive effects during the day, its negative effects on sleep at night should not be ignored. To get the benefits of blue light and minimise its negative effects, it is recommended to limit exposure to screens and blue light-emitting devices for at least 2 hours before bedtime and to use blue light blocking technology, such as special filters and glasses. Additionally, it is important to get exposure to natural light during the day, especially in the morning, to help regulate the body’s natural circadian rhythm and promote healthy sleep.

Main Points

What you can take away from this

  • Disrupts Circadian Rhythm: Blue light is highly disruptive to the body’s natural circadian rhythm, which is the internal body clock that regulates sleep and wakefulness. Exposure to blue light at night disrupts the release of melatonin, a hormone that regulates sleep, leading to insomnia and poor sleep quality.
  • Increases Alertness: Blue light stimulates the brain, increasing alertness and reducing the body’s ability to relax and prepare for sleep. This can lead to difficulty falling asleep and poor sleep quality, leaving individuals feeling tired and fatigued during the day.
  • Impairs Performance: Poor sleep quality caused by exposure to blue light can impair cognitive performance, making it difficult to focus, concentrate, and be productive. This can impact work, school, and daily activities.
  • LED lights that have a colour temperature of 2700K or lower are considered warm and emit less blue light.
  • Warm-toned lighting, such as incandescent bulbs, salt lamps are a good alternative to standard LED bulbs

A Bit More Detail

What does this really mean in simple terms

Blue light is a type of high-energy visible (HEV) light that is emitted from electronic devices such as smartphones, computers, LED bulbs and televisions. The blue light wave length is between 400 to 490 nanometers and it is considered to be the most disruptive type of light for sleep. This is because it interferes with the circadian rhythm, the body’s natural sleep-wake cycle, and suppresses the production of the sleep hormone melatonin.

Detection of Blue Light: The eyes contain specialized photoreceptor cells known as rods and cones, which are responsible for detecting light and transmitting signals to the brain. In addition to rods and cones, the eyes contain a type of photoreceptor called melanopsin ganglion cells, which are sensitive to blue light. These cells play a crucial role in regulating the circadian rhythm and signaling the brain to secrete melatonin.

Impact on Sleep: Exposure to blue light at night has a significant impact on sleep quality and quantity. Research has shown that blue light exposure can reduce the production of melatonin, making it more difficult to fall asleep and stay asleep. This can result in decreased sleep duration, increased wakefulness during the night, and decreased alertness and cognitive function during the day.

Moreover, blue light exposure can affect the quality of sleep by decreasing the production of slow wave sleep, which is important for physical restoration, and increasing the production of REM sleep, which is important for mental restoration. This can lead to a decrease in overall sleep quality, leading to daytime fatigue and decreased productivity.

Types of Lighting to Use Instead: To minimize the effects of blue light on sleep, it is recommended to reduce or eliminate exposure to blue light from electronic devices in the hours leading up to bedtime. Instead, it is recommended to use warm-toned lighting, such as incandescent bulbs, salt lamps, or candlelight, which do not emit blue light. Additionally, blue light blocking glasses can be worn to reduce the amount of blue light reaching the eyes.

Deeper Dive

When you just want to know stuff

Melatonin and Blue Light:

Melatonin is a hormone that regulates sleep and wake cycles and its production is influenced by light exposure, particularly blue light. Blue light suppresses the production of melatonin and has a negative impact on the sleep-wake cycle.

Light Detection in the Eye:

The eye has two types of photoreceptor cells, rods and cones, that detect light and send signals to the brain through the optic nerve. Rods are responsible for detecting light levels, including the presence of blue light, and sending signals for adaptation to the changing light environment. Cones, on the other hand, are responsible for color vision and detailed visual perception.

Impact on Sleep:

The brain processes information from the eye about light exposure and adjusts the production of melatonin accordingly. Exposure to bright light, particularly blue light, during the day can suppress melatonin production and make it harder to fall asleep at night. On the other hand, exposure to dim light or darkness at night can increase melatonin production and promote sleep.

Production and Purpose of Melatonin:

Melatonin is produced by the pineal gland in the brain, which receives signals from the suprachiasmatic nucleus (SCN), a small region of the hypothalamus that acts as the body’s “biological clock”. The SCN monitors the light-dark cycle and regulates the production of melatonin. The purpose of melatonin is to regulate the sleep-wake cycle and promote sleep. Melatonin levels are highest at night and lowest during the day, regulating the timing of sleep.

Key Points:

  • Photoreceptor cells: Specialized cells in the retina of the eye that respond to light and send signals to the brain through the optic nerve.
  • Suprachiasmatic Nucleus (SCN): A small region of the hypothalamus that acts as the body’s “biological clock” and regulates the production of melatonin by monitoring the light-dark cycle.
  • Pineal Gland: A small endocrine gland in the brain that produces melatonin.
  • Hormone: A chemical messenger produced by the endocrine glands that regulates various physiological processes in the body.
  • Chronobiology: The study of the biological processes, including the sleep-wake cycle, that are regulated by an organism’s internal “biological clock”.
  • Circadian Rhythm: The 24-hour cycle of physiological processes that occur in living organisms, including the sleep-wake cycle, regulated by the body’s internal “biological clock”.

What are Melanopsin Cells?

Melanopsin is a type of photopigment found in specialized cells in the eye known as intrinsically photosensitive retinal ganglion cells (ipRGCs). These cells are part of the retinal ganglion cells and are responsible for detecting changes in light intensity and sending signals to the brain about the light environment.

What do Melanopsin Cells Do?

These special cells are especially sensitive to blue light and play a key role in regulating our sleep-wake cycle. They send signals directly to the hypothalamus and the suprachiasmatic nucleus (SCN), which acts as our internal “biological clock”, to help regulate the timing of sleep and wakefulness.

In addition to regulating sleep, melanopsin cells also play a role in controlling other daily processes like pupil size, the suppression of cortisol, and the regulation of the autonomic nervous system.

So, in short, melanopsin cells are critical for helping our body keep track of the light and dark and regulating our sleep-wake cycle and other daily processes.

About the terms I’ve used:

  • Photopigment: A pigment that is sensitive to light and helps detect changes in light intensity
  • Intrinsically photosensitive retinal ganglion cells (ipRGCs): Specialized cells in the eye responsible for detecting changes in light intensity and sending signals to the brain about the light environment
  • Suprachiasmatic Nucleus (SCN): The part of the hypothalamus that acts as the body’s “biological clock” and regulates the sleep-wake cycle
  • Retinal ganglion cells: Cells in the eye that are responsible for transmitting signals from the retina to the brain
  • Autonomic nervous system: The part of the nervous system responsible for regulating unconscious functions, such as heart rate and digestion
  • Cortisol: A hormone produced by the adrenal glands that helps regulate metabolism, the immune system, and stress responses

Online papers you might like to have a look at:

Manageable Sleep Goals

Making a positive change a little bit at a time

  1. Reduce evening light exposure:
    Reduce the amount of blue light exposure in the evenings by turning off electronic devices (e.g. smartphones, computers, televisions) at least an hour before bedtime. If necessary, use blue light blocking technology or wear blue light blocking glasses to further reduce exposure.
    You can reduce your exposure to blue light gradually, ten minutes longer every other day until you reach your goal of one hour. The key here is to reduce exposure gradually this way your more likely to keep this new routine.

  2. Increase daytime light exposure:
    Increase exposure to natural light during the day by spending time outside or near a window. This can help regulate the circadian rhythm and improve the production of melatonin. Just make sure you have exposure to daylight and this must be light into the eyes (NOT looking directly at the sun). Just ambient outdoor natural light, even on a cloudy day this will expose you to fare more light than anything indoors.