Moonlight vs. Blue Light: The Battle for Better Sleep

According to the Vision Council, 80% of American adults spend over two hours a day using digital devices. Additionally, almost 67% use two or more devices simultaneously.¹

Besides using cell phones, most people also engage with computers or tablets for work and unwind by watching TV or playing video games. That's a lot of screen time!

While staring at a screen is part of most people's everyday lives, it can also affect our health.

For instance, about 59% of people experience symptoms of digital eye strain, as noted in the same study by the Vision Council.¹ Extended screen use may also affect sleep quality.*

How blue light may hurt your sleep patterns.*

Sleep is essential for emotional regulation, mood stability, and cognitive performance². Insufficient sleep can impair the brain's ability to manage emotions, making individuals more reactive to stress and reducing their capacity to cope with negative feelings.*

This disruption is closely linked to mood challenges such as feeling low and nervousness, as poor sleep can alter brain function and neurotransmitter levels, including serotonin and dopamine, which are essential for mood regulation.*³

Sleep quality also heavily impacts cognitive processes like memory, attention, and decision-making. Sleep facilitates memory consolidation and supports the prefrontal cortex's functioning, which governs high-level thinking and judgment.*

Over the past decade, research has increasingly shown that artificial blue light, especially at night, can exacerbate these issues by disrupting the natural sleep-wake cycle.*

Here's an example. A 2014 study found that individuals who read e-books before bed experienced more disrupted sleep patterns and felt more tired the next day compared to those who read traditional books.⁴

This effect is likely due to blue light's influence on REM (rapid eye movement) sleep, a deep sleep phase crucial for memory consolidation.*

Further supporting this, a 2019 review in the Journal of Biological and Medical Rhythm Research highlighted that blue light, more so than other colors of light, can disrupt melatonin production.*⁵

Why is this relevant?

Because melatonin (a hormone that signals to our brain that it's time to sleep) begins to rise naturally about two hours before we sleep and remains elevated during the night.

Exposure to blue light during this period can suppress melatonin secretion for twice as long as the immediately longer green wavelength of light, thereby delaying sleep onset and reducing sleep quality.*

So why this reaction to artificial blue light? Well, it's largely because our eyes are not very effective at blocking blue wavelengths.

So, almost all of it passes through to the retina at the back of our eye, which helps our brain translate light into images. This exposure can alter how our brain interprets light, affecting our sleep.

While natural light helps regulate our sleep-and-wake cycle or circadian rhythm, blue light has a more potent effect on disrupting our body's readiness for sleep by interfering with melatonin production.*⁶

HCF® takeaway: Blue light exposure close to bedtime can make you less drowsy and extend the time it takes to fall asleep. However, occasional brief encounters with blue light, like sending a text at night, are unlikely to cause significant sleep disruption.*

Light in the morning vs. light at night: which should you avoid?

The impact of blue light on sleep varies depending on the timing of exposure. Exposure to blue light in the morning and throughout the day can help reduce daytime fatigue and enhance mood for those active during daylight hours.

However, exposure to blue light before bedtime is widely believed to negatively affect both sleep quality and mood.*

Morning light, particularly blue light, plays a crucial role in regulating circadian rhythms.* Daytime sunlight actually emits a higher concentration of blue light than what is observed at sunset.

In fact, experts often advise night shift workers to avoid bright light in the morning after their shift ends, as it can disrupt their essential daytime sleep.⁷

Exposure to blue light at night can interfere with the sleep-wake cycle, making it challenging to both fall asleep and stay asleep. Since light suppresses melatonin production, nighttime light exposure can significantly hinder your ability to fall asleep.*⁷

Even minimal amounts of light at night can disrupt the body's natural pattern of darkness at night and light during the day.