Circadian Chaos
The dark side of modern light
Modern light bulbs, phones, tv’s, computers, fridges, street lamps, and other sources emit a wavelength of light that disrupts your inner clock. Until the invention of artificial lighting, people mostly spent their evenings in darkness. The sun was the main source of light, and once it went down, people illuminated their evenings with candles, oil lamps, gas lamps, and regular fires. When was the last time you relied on a candle when it was dark at night? Nowadays, the sun goes down and you flip the light switch. You might spend your evenings watching a show, movie, scrolling on your phone, or doing work on the computer. Most people look at a screen until the very second they go to sleep. Evenings are now easily illuminated, which is a great convenience, but also comes with a price.
The suprachiasmatic nucleus (SCN) is a brain region located in the hypothalamus. It acts as the body's master clock, regulating sleep-wake cycles along with a wide range of other physiological processes. This master clock is responsible for aligning the internal biological rhythms (like the circadian rhythm) of an organism with the external environment. The internal clock is synchronized with the external environment through cyclic environmental cues, a process known as entrainment. These signals or cues are called zeitgebers, or time givers. Light is the primary zeitgeber in the circadian system. As specialized cells in the retina detect light, they send the photic information to the SCN, where it adjusts its internal clock to align with the external light-dark cycle. Once processed, the SCN relays this message to a network of peripheral clocks throughout the body.
Darkness stimulates the pineal gland to release melatonin, the hormone that promotes sleep. Conversely, exposure to light, especially blue wavelengths, suppresses melatonin production and disrupts the circadian rhythm and timing of sleep.
Blue light is the light emitted from most light bulbs and screens. The sun also emits blue light, and is actually very important for our bodies to receive. It helps regulate our circadian rhythm, promotes wakefulness by stimulating the release of cortisol, and makes us more alert. Blue light from the sun is balanced by all other colors that naturally occur in the full spectrum of sunlight, such as the shorter and lower energy wavelengths of red and orange light. Blue light from the sun is only received during the day, when we are meant to be awake and alert. One of the major issues of light from screens and bulbs is the distorted spectrum of light they emit, which lacks balancing red and orange wavelengths. The other issue is that artificial blue light is available to us at any time we choose, day or night. Exposure to blue light at night tricks the brain into thinking it is daytime. As was natural for thousands of years, the only time our bodies expect to receive blue wavelengths is when we are in tune with Earth's natural light cycle.
Blue light at night is one of the many reasons why our sleep quality and quantity suffers. Regularly disrupting the circadian rhythm can have significant consequences on sleep and overall health.
Fortunately, you don’t have to live your nights in total darkness or ditch all of the screens once the sun goes down. Here’s what you can do:
Switch to warmer wavelengths of light at night: Use candles or red bulbs/lamps that do not emit blue light.
Use blue light filters on screens: To reduce blue light on an iPhone, go to Settings → Accessibility → Display & Text Size → Color Filters.
Select Color Tint and turn the intensity all the way up and the hue all the way down. Then go to Accessibility Shortcut and select Color Filters. With this feature selected, your screen will turn red when the side button is triple clicked. F.lux is a software that adapts your computer screen to the time of day. Simply download the software for free at justgetflux.com.
Wear blue light blocking glasses at night: High quality blue light glasses block out the wavelengths disruptive to sleep. Purchase blue light blockers from brands that test their glasses using a light spectrometer and block 100% of light between 400-550 nm. Trustworthy brands are Ra Optics and Bon Charge. Look for red tinted glasses for nighttime use and yellow tinted lenses for daytime computer use.