Blue Light and the Functioning of Human Brain

We always quantify the world as percentages of light and darkness but what we may not know is that even light has different spectra. Light waves are photons of energy that constitute, in general, the visible and invisible spectra of light. While we have radio waves, microwaves, infrared, x-rays, ultraviolet light, and gamma rays on the invisible spectrum, we have coloured waves on the visible spectrum. The beauty of the visible spectrum is often manifested when visible light gets dispersed as a rainbow, a phenomenon that captivates millions.

You may remember from basic biology that even though we have Red, Orange, Yellow, Green, Blue, Indigo and Violet waves the human eye has receptors for Red, Green and Blue lights only. These receptors are cells present on the innermost layer of the human eye known as retina and are called cones. While cones are responsible for detailed and coloured reception there are other cells which are responsible for rapid, black, and white and broader field of vision called rods. Both these cells are responsible for most of the vision and relay signals to the brain where they are perceived. There are yet a few other cells which relay some information to the brain as well. Of all these cells, the neurons that consist of melanopsin are of particular interest since these, along with some influence of rods and cones, control the sleep cycle.

Normally all light spectra enter the eye, but most are filtered and blocked by the other layers of the eye. A few rays however do enter the retina and even though all spectra of light are not perceived by the brain they stimulate the neurons in the retina. Consequently, the retina stimulates the brain and is responsible for alertness, concentration, and functioning. Throughout the day the light rays on the retina relay to the brain and inhibit the production of a neurotransmitter called melatonin which is responsible for sleep and regulation of mood. During night, it increases in concentrations and is released as part of the circadian rhythm.

The green and red lights are protective for the retina and promote sleep induction through melanopsin. Meanwhile melanopsin is particularly sensitive to blue light and it causes arousal and sleep deprivation. It is also responsible for agitation and aversion to blue light and counteracts the role of melatonin by producing a hormone called corticosterone under the influence of blue light. Furthermore, blue light causes significant damage to the retina by causing breaks in the cellular DNA and slowing down the healing processes. Studies suggest that 2h of exposure to blue light can cause significant damage to the retina.

Approximately 60% of the population spends at least 6 hours on electronic media that utilize blue light. Most of the laptops, televisions, LED, mobile phones, and other smart gadgets emit blue light which is particularly damaging to the eye. What’s worse is that even though 30% of the world’s population suffers from some form of insomnia, a vast majority use these modalities which exacerbate their conditions. Sleep deprivation in turn causes fatigue, restlessness, hypertension, heart conditions, chemical imbalances, and mental disorders. Poor quality of sleep also impacts memory and impairs an individual’s functioning, affecting all domains of life. It is one of the most significant reversible risk factors for Alzheimer’s (a disease). Other than causing insomnia blue light causes agitation and stress responses in the human body through production of corticosterone. Corticosterone affects the brain at a cellular level and is responsible for worsening mental disorders like depression, anxiety, sleep related disorders and stress related disorders. Furthermore, corticosterone shifts the body’s natural balance to higher glucocorticoid levels predisposing to hypertension, diabetes, obesity, heart diseases and infections.

While there are companies utilizing the latest research and offering devices with blue light filters and reduced usage of blue lights, it is essential that we make changes in our daily life that may improve our sleep and health. Utilizing sleep hygiene is still the most important step before medications or supplements can be considered for sleep related disorders. A few changes that can be made in daily lives are:

Even though lifestyle changes may benefit at an early stage, they may not be sufficient when dysfunction is more and going to a doctor may be essential.