Let there be light!

Light is a pillar of life. From the human brain perspective, light is responsible for vision, and it plays an essential role in the brains biologic function, including circadian rhythm and sleep. The rhythm of the sunrise and sunset serves as a sleep-wake to the body. The widespread use of artificial light after sunset disrupts the circadian rhythm and contributes to sleep such as insomnia. If you just have to look at your phone screen at night, here is a tip. *

Visual light reaches the brain by entering the eye, hitting the retina at the back of the eye where it is converted into electrical signals by photoreceptor cells. The axons of some of these cells exit the retina to form the optic nerve, which travels to two places: the thalamus (specifically, the lateral geniculate nucleus, or LGN) and the superior colliculus. The LGN is the main relay for visual information from the retina to reach the visual where the signals and interprets them as images, or what you see. 

Red and blue light are both part of the visible light spectrum. Red light has a wavelength of around 620 to 750 nanometers (nm). Red light has the longest wavelength and lowest energy of visible light. Blue light has a wavelength of around 380 to 500 nm. Blue light has the shortest wavelength and highest energy of visible light. Red light and blue light both enter the brain via the retina. Red light, particularly within the near-infrared spectrum, has a longer wavelength which allows it to penetrate deeper through tissue like the skull compared to other light colors and to reach the brain tissue directly.

Red Light and Blue Light have different effects on the brain. When it comes to nighttime exposure, a dark room is best. Red light is generally considered better than blue light because blue light can significantly disrupt your sleep cycle by suppressing melatonin production, while red light has minimal impact on your circadian rhythm,
making it a more sleep-friendly option. This is because when blue light gets in the brain, it affects specific retinal cells called photosensitive ganglion cells which contain melanopsin, a pigment particularly sensitive to blue light. These cells send electrical signals along the optic nerve to the brain’s suprachiasmatic nucleus (SCN), which controls circadian rhythm and sleep-wake cycles. Exposure to blue light, especially at night, can disrupt sleep patterns by suppressing melatonin production and signaling to the brain that it is daytime. Red light, on the other hand, is less disruptive to the circadian rhythm compared to other light colors, allowing for the continued production of melatonin, the sleep hormone and promoting relaxation and better sleep quality. Red light also has a calming effect on the nervous system, potentially reducing anxiety and promoting relaxation before sleep. 

Blue light: 
-Suppresses melatonin production. 
-Disrupts circadian rhythm, making it harder to fall asleep. 
-Often emitted from electronic devices like phones and computer screens.
 
Red light: 
-Minimal impact on melatonin production. 
-Less disruptive to the sleep-wake cycle. 

Red light has another beneficial effect to the body, including the brain. Red Light Therapy is a type of Photobiomodulation, a type of treatment that uses light energy toregulate biological processes in the body.

Red light in wavelengths of 650-800nm affects mitochondrial complex IV or cytochrome oxidase to increase the rate of formation of ATP resulting in the generation of a number of beneficial factors. In this way, red light stimulates mitochondria function, the energy- producing units within cells, to produce more ATP, which, amongst other beneficial things, may help with clearer thinking and production of neurotransmitters. This realization has increased the popularity of red-light beds and infrared saunas.

Some of the brain health and performance benefits of red-light therapy include: 

Increased blood flow
Red light therapy can increase blood flow in the brain, which may help with brain repair and optimization. 

Improves mitochondria function
Red light therapy can stimulate mitochondria, the energy-producing units within cells, to produce more ATP, which may help with clearer thinking and production of neurotransmitters. 

Enhances neural processes
Red light therapy can enhance the natural processes of mitochondria, including neural mitochondria, which helps produce neurotransmitters like serotonin and dopamine. 

May help with a range of conditions
There is some evidence that red light therapy may help with a range of conditions, including traumatic brain injuries, degenerative diseases, and psychiatric disorders.

May be used for cognitive enhancement
There is even the possibility that PBM could be used for cognitive enhancement in healthy people. 

I will end with a couple key points:

1. We need light for healthy body functions. I don’t think anything beats the warm feeling of sunlight on my face, especially the morning light from the east. Morning light seems to rev me up for the day. I live in an area that is beautiful, and sun filled in the summer, but dark in the winter. I use a red-light bed to supplement my lack of winter light.
2. A dark room is best for sleep, however, when it comes to nighttime light exposure, blue light is significantly more disruptive to sleep than red light; blue light tends to suppress melatonin production, signaling to the body that it’s daytime, while red light has minimal impact on the sleep cycle, making it a better choice for nighttime illumination. Exposure to red light during sleep and upon waking can reduce the likelihood of feeling tired and disoriented in the morning, known as sleep inertia.

How apropos that this “The Tall Spine” blog edition comes out at about the shortest daytime of the year! Let there be light!

Until next tine,

Jeffrey Larson, MD
The Tall Spine

*Protip – your iPhone may be affecting your sleep. Here is a quick trick as to how to change your screen to a red-light screen at nighttime. To turn your iPhone screen red, you can enable a red color filter: 

1. Go to Settings
2. Select Accessibility
3. Select Display and Text Size
4. Select Color Filters
5. Enable Color Filters
6. Select Color Tint as the filter type
7. Slide the intensity and hue all the way to the right You can also create a shortcut to quickly switch between your regular screen and the red tint: 
8. Go to Settings > Accessibility > Accessibility Shortcut > Color Filters
9. Press the right-side button three times to turn your screen red
10. Press the right-side button three times again to go back to your regular screen