09/19/2021
By Denis Ivanchuk - health Ranger
Blue light and its detrimental effects
What we call light is just electromagnetic radiation that’s visible to the human eye. [1] Radiation is, in most basic terms, just energy that travels, spreading out as it goes. Electromagnetic radiation is generated by changes in movement (vibrations) of electrically charged particles, which travel in waves. These waves vary in length and make up the electromagnetic spectrum. The light that comes from a lamp and the radio waves that come from a radio station are just two of the many types of electromagnetic radiation. [2]
Light that’s visible to the naked eye has a wavelength that ranges from 380 to 750 nanometers (nm). When all wavelengths of visible light are combined, you get white light. Sunlight on a clear day is an example of natural, full-spectrum white light. White light can also be separated into different color bands based on wavelength. The main color bands within white light are blue, green, yellow, orange and red. [3]
The wavelength of each light ray determines both its color and the energy it emits. Light rays with long wavelengths belong to the red end of the visible light spectrum. They generally emit less energy than light rays at the blue end of the visible light spectrum. These blue light rays have shorter wavelengths that range from 380 to 500 nm and produce high amounts of energy. About one-third of all visible light is blue light.
This blue light is scattered everywhere when particles that make up high-energy, short-length waves collide with air molecules as sunlight travels through the atmosphere. In fact, this is what makes the sky appear blue. Natural blue light helps regulate your body’s sleep-wake cycle, or circadian rhythm. [4] This 24-hour cycle is what lets your body know when to carry out essential functions. [5]
Different systems of your body follow circadian rhythms that are synchronized with a “master clock” in your brain. This master clock is directly influenced by environmental cues, particularly light. As such, circadian rhythms are intricately tied to the cycle of day and night. The synchronization between the master clock and circadian rhythm is crucial for maintaining optimal health because it greatly influences your brain function, mood and sleep quality.
Unfortunately, due to the widespread use of electronic devices, we are constantly exposed to high amounts of artificial blue light. While all types of visible light can affect our circadian rhythm, blue light has the largest impact. [6] This is because blue light stimulates parts of the brain that make us feel alert. It also elevates our body temperature and increases our heart rate. During the day, these can be helpful if we need to concentrate and carry out tasks.
The problem occurs at night when blue light suppresses the release of melatonin. Often referred to as the “sleep hormone,” melatonin is a hormone that your pineal gland produces in response to darkness. It helps regulate your sleep-wake cycle. As such, your blood melatonin levels increase at night then drop in the morning when the sun comes up. [7]
Because it suppresses the release of melatonin, exposure to artificial blue light at night tricks your brain into thinking it’s still daytime, effectively disrupting your circadian rhythm and making you feel alert instead of sleepy. This process starts in the retina of the eyes, particularly with cells called retinal ganglion cells. When these cells are stimulated by blue light, they produce melanopsin, a photopigment that suppresses melatonin production.
In one study, researchers from Harvard University conducted an experiment comparing the effects of 6.5 hours of exposure to blue light with the effects of 6.5 hours of exposure to green light, a wavelength useful for photosynthesis. They found that blue light suppressed melatonin production for twice as long as green light did. It also shifted circadian rhythms by as much as three hours, while green light only shifted circadian rhythms by 1.5 hours. [8]
A misalignment of your circadian rhythm can lead to sleep problems and many serious health issues. For instance, an animal study presented at Neuroscience 2009, the annual meeting of the Society for Neuroscience, found that disruptions to the circadian rhythm of mice caused weight gain, impulsive behavior and other physiological changes similar to those observed in people who experience jet lag. [9]
The researchers also observed that mice with disrupted circadian rhythms were slower at solving new mazes than mice with properly aligned circadian rhythms. In addition, the brains of the affected mice were smaller and had fewer complex brain cells in the medial prefrontal cortex. This area of the brain is involved in executive function and helps regulate mental flexibility.
Meanwhile, according to a review published in the journal Reviews in Endocrine and Metabolic Disorders, circadian misalignment can also lead to cardiometabolic changes that could eventually lead to heart disease. [10] This is because cardiovascular function is partly influenced by the body’s circadian rhythm. The review also found that changes in a person’s sleep-wake cycle may worsen pre-existing heart conditions.
Aside from your body’s sleep-wake cycle, your eyes are also greatly affected by exposure to blue light. High-energy blue light scatters more easily than other types of visible light. Because digital screens emit a lot of blue light, this scattered visual “noise” reduces contrast and contributes to digital eye strain. Prolonged exposure to blue light can also damage the retina and contribute to age-related macular degeneration, which can eventually lead to loss of vision. [11]
In addition, people tend to blink less when using electronic devices, which can lead to dry eye and contribute to digital eye strain. Other signs of digital eye strain include blurred vision, headaches and neck and shoulder pain. [12] All these adverse events can be triggered by chronic exposure to artificial blue light emitted by electronic devices, especially if these devices are used before bedtime.
