Our bodies are conditioned to be alert during the day and sleepy at night. This phenomenon is also known as our circadian rhythm, or sleep-wake cycle.
Light suppresses the production of the sleep-inducing hormone melatonin, leading to poor sleep.
Blue light, in particular, from electronic devices can be especially problematic if we have the habit of scrolling through our phones late at night.
Light and the Circadian Rhythm
When optic nerves perceive light, they send signals to the Suprachiasmatic Nucleus (SCN). The SCN is located in the hypothalamus and regulates our circadian rhythm by controlling the pineal gland. The pineal gland produces melatonin, but only when our optic nerves perceive darkness.
Light from electronic devices signals our brain to suppress melatonin production, which is why staying up late watching TV or scrolling on your cell phone can make it harder to fall asleep and get good quality rest. With less sleep comes more daytime drowsiness, ultimately impacting your day-to-day productivity.
Effects of Blue Light
Natural sunlight and indoor lighting contain a mixture of different wavelengths, including short-wavelength blue lights. Research shows that blue light from the sun or an artificial source can keep you alert and enhance your performance and mood.
The timing of blue light exposure is a critical factor in keeping your circadian rhythm running smoothly. Blue light positively affects you during daytime hours, keeping you alert and energized, but exposure to blue light at night inhibits the production of melatonin, making it harder to fall asleep and stay asleep.
Artificial Sources of Blue Light
- Computer screens
- E-book devices or e-readers
- Fluorescent and energy-efficient LED lights
Reducing the Effect of Blue Lights
It may be difficult to stay off electronic devices in today’s hectic society, since many rely on them for work or leisure—from checking reports and sending emails to reading e-books or scrolling through social media sites. The blue light from these devices tricks your brain into thinking it’s still light outside and that you should be up and active, resulting in increased alertness.
There are different ways to prevent devices from ruining your night’s sleep. Blue light filtering glasses, night mode settings, and smart bulbs can all save your circadian rhythm from blue light. It also helps to spend more time outside during the day and avoid screens as much as you can at night.
Amber tinted glasses filter out the blue light. According to a 2017 study, people who wore blue-light-blocking glasses three hours before sleep for two weeks saw positive results—their nighttime melatonin production increased by 58 percent, resulting in participants falling asleep faster and sleeping 24 minutes longer.
Studies have shown that wearing blue-light-blocking glasses while using electronic devices does not suppress melatonin production. Participants produced as much melatonin as they would have in a dark room.
Night Mode Apps
You can install programs on your computer to automatically adjust its brightness and hue. Once evening rolls around, your computer will dim its brightness and block blue light, giving off an orange tint, instead. Red and orange are on the opposite side of the electromagnetic spectrum from blue and are the least sleep-disrupting.
You can download similar apps on your smartphone and other electronic devices to block blue light and get better rest.
Spending Time Outdoors During Daytime
Spending more time in natural daylight makes the contrast between day and night clearer to your brain, reducing the chances of sleep disruptions caused by blue light-emitting devices. If you can’t afford to spend time outside during the day, soak in the sun by sitting close to a window or consider light therapy.
Light therapy involves sitting by high-intensity, white artificial lights, mimicking sunlight. Light therapy acclimates your brain to day and night.
Using Smart Bulbs
Smart bulbs dim brightness and adjust hues. These light bulbs change to warmer colors as the evening progresses to night, moving from short-wavelength blues to warmer tinges of orange.
Avoiding Screen Time an Hour Before Bedtime
Avoiding any screen time at least an hour before bed prevents blue lights from affecting you. Your body and brain have time to trigger melatonin production, inducing restful sleep.
You can engage in a healthy bedtime routine by taking a warm bath and reading a book, promoting better sleep.
Comparing Light-Intensity From Various Sources
There is a glaring contrast between sunlight and artificial light. If you are exposed to more sunlight, your body builds a natural defense mechanism against blue light—light intensity from artificial sources is less than natural light.
Light intensity is measured by “Lux,” factoring in distance, brightness, and area.
This table indicates the difference in illuminance in various natural and artificial settings.
|Light Sources||Approximate Illuminance (In Lux)|
|Full Moon Night||1|
|Typical Office Light||500|
|Electronic Devices||38 to 1 (with laptops being more than tablets or tv)|
Does blue light affect children and adolescents more?
Adolescents are more sensitive to blue lights than adults because of their changing hormones. Children who spend more time in the sun, or have no history of sleep problems are less likely to be bothered by blue light from electronic devices. Limiting screen time in children is recommended for their eye health and it keeps them active—naturally tiring them out for bedtime.
Which electronic device emits the most light?
Bigger screens like laptops are known to emit more light than tablets or smartphones. Televisions have the biggest screens, but blue light is less harmful because of its distance from the viewer. Ideally, it is best to avoid all electronic devices at least an hour prior to bedtime.
Why does blue light affect sleep?
Blue light comprises a significant portion of natural sunlight, promoting wakefulness and suppressing sleep-inducing melatonin. Blue light emitted from electronic devices trick our brain into perceiving night as day, suppressing melatonin production—and lower melatonin levels impact sleep quality and duration.
Blue light from digital devices affects melatonin levels by hindering its production, making it harder to fall asleep and stay asleep. It’s safer to refrain from using these devices an hour before bed to ensure better sleep. Staying up late and scrolling through your phone can disrupt your sleep and lead to daytime drowsiness.
This article is for informational purposes and should not replace advice from your doctor or other medical professional.