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How Blue Light Affects Kids’ Sleep

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Alexa Fry

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Dr. Anis Rehman

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Electronic devices have become an integral part of most children’s lives. Kids use screen-based electronics throughout the day for schoolwork, entertainment, communication, and more. While technology offers countless educational and social benefits, there are also downsides to our widespread, easy access to these devices. One concern is the impact technology may be having on sleep.

As technology became commonplace in day-to-day life, sleep quality in children suffered. Approximately one third of children and more than half of adolescents do not get enough sleep. There are a few ways that evening and nighttime access to electronic devices could affect how much kids sleep. Spending more hours of the night on screens leaves fewer hours for sleep, and stimulating content could decrease sleepiness. Another mechanism through which electronics may affect sleep through the blue light emitted by these devices.

What Is Blue Light?

The full spectrum of visible light consists of varied light wavelengths. Violet light has the shortest wavelength, while red light wavelengths are the longest. Blue light is a short wavelength type of light that promotes alertness and performance. Blue light is also the most important regulator of our sleep-wake cycle or circadian rhythm.

What Are Common Sources of Blue Light?

The screens of televisions, smartphones, tablets, computers, gaming systems, and certain e-readers all produce artificial blue light. However, we aren’t exposed to blue light solely through electronics. We get most of our blue light exposure from the sun. Additionally, light-emitting diode (LED) and fluorescent light bulbs — which have become increasingly common in homes due to their energy-efficiency — produce blue light.

Blue Light and Melatonin

Melatonin is a hormone that promotes feelings of sleepiness, and blue light suppresses the production of melatonin. Humans evolved to maintain a sleep-wake cycle based around the rising and setting of the sun. When we are exposed only to natural light from the sun, melatonin levels are low during the day, begin to increase in the evening following sunset, reach their peak in the middle of the night, and then gradually decrease until morning.

Exposure to blue light during the day from sunlight or other sources is a healthy promoter of energy and concentration. Daytime blue light exposure has also been shown to improve sleep quality and duration. However, using devices that produce artificial blue light in the evening and nighttime disrupts our natural sleep-wake cycle by tricking the brain into not producing melatonin before bed. This causes us to feel less sleepy than we should at bedtime.

How Does Blue Light Affect Children?

The general principles of light affecting melatonin production and sleep apply to both children and adults. However, children may be even more sensitive to light. As we age, structures in our eyes gradually become less sensitive to light. Children also have larger pupils than adults. A research study found that evening light exposure suppressed melatonin twice as much in children compared to adults. A child’s age and developmental stage may also determine the impact. Researchers found that children who had not yet gone through puberty experienced significantly more melatonin suppression in response to evening light compared with post-puberty adolescents.

    Does Blue Light Cause Sleep Issues in Children?

    Observational studies from around the world have shown that screen use by children is associated with later bedtimes and less time spent asleep. While these observational studies cannot prove a cause-and-effect relationship, numerous studies in adults have demonstrated that light exposure in the evening and the use of blue light-emitting devices before bed affect sleep. This evidence, combined with the data showing that children have an increased sensitivity to light-related melatonin suppression, suggests that the sleep-disrupting effects of blue light may apply to children as well.

    However, more research is needed to illuminate whether blue light causes disrupted sleep or if children who already struggle with sleep are more likely to use screens (and be exposed to blue light) before bed and at night. It is possible that these two factors may share a bidirectional relationship, meaning that sleep affects screen time use, and screen time use affects sleep.

    Effects of Sleep Loss in Kids

    While the relationship between evening blue light exposure and sleep in children requires further investigation, the important role sleep plays in childhood functioning and development is well-supported by scientific evidence. Research has shown that sleep loss is linked with inattentiveness, impulsivity, and difficulty self-regulating. Children who don’t get sufficient sleep are also at risk for poorer school performance. The symptoms of sleep loss in children often mirror the symptoms of attention deficit hyperactivity disorder (ADHD), which may lead to a misdiagnosis of ADHD in some sleep-deprived children.

    Certain hormones that help with muscle mass, a healthy immune system, and cell repair are released during sleep, so these functions may also be impacted in children who are not sleeping enough.

    How Can You Reduce Exposure to Blue Light?

    Given the importance of sleep for a child’s mental and physical health, ensuring that children are consistently getting enough sleep at night is critical. If you are concerned about the impact blue light exposure may be having on your child’s sleep, there are a number of steps you and your child can take. Start by trying the following interventions:

    • Set a technology curfew: Establish a nightly schedule that involves ceasing the use of electronics one hour before bedtime. You can use an alarm to help a child remember to turn off screens at a certain time. It might help to plan other calming activities before bed, such as reading, puzzles, coloring, painting, or stretching. Parents should also lead by an example and limit the use of screens prior to bedtime.
    • Create technology-free zones: Storing phones and other devices outside of the bedroom, and especially away from the mattress, may be a difficult transition for some kids, but it can have a big impact on nighttime blue light exposure. It reduces the temptation to use devices before going to sleep and eliminates the possibility of being woken up by texts, calls, and other alerts.
    • Use blue light filters: Special glasses that filter out blue light may help combat the adverse effects of blue light exposure before bed. Blue light-filtering apps are also an option. They shift the color tone of a tablet or smartphone screen toward warmer wavelengths of the light spectrum.
    • Alter settings: Many electronic devices include options for “night mode” or “dark mode” that change the screen background to black, reducing blue light exposure.
    • Switch to red lights: Red light exposure does not suppress melatonin production, so it could help to use red light bulbs for evening reading lamps and nightlights. Yellow light and orange light are also on the long wavelength end of the light spectrum and could be good options.
    • Ensure daytime light exposure: Getting exposed to bright light during the day helps to synchronize circadian rhythms and promotes sleepiness at bedtime. Make sure your child gets plenty of bright, natural, daytime light.

    It can be a struggle to navigate setting rules and boundaries around screen use, especially in teens. Talk with your child or teen frequently about the role of sleep in their physical and emotional health and the harmful effects blue light may have on sleep. It might help to work together on establishing rules for technology use. Parents and guardians can also model healthy sleep habits, including following a technology curfew and storing electronics outside the bedroom.

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