How Blue Light Really Affects Your Sleep and Health

Natural sunlight contains a range of red, orange, yellow, green, and blue light rays. Each of these colors has many shades, depending on the energy and wavelength of the individual rays. Combined, this spectrum of colored light rays creates what we call "white light" or sunlight. Without getting into complex physics, there is an inverse relationship between the wavelength of light rays and the amount of energy they contain. Light rays that have relatively long wavelengths contain less energy, and those with short wavelengths have more energy. Rays on the blue spectrum have shorter wavelengths, and thus more energy.  

For that reason, blue light rays are considered beneficial during daylight time, because they boost attention, mood, and reaction times. It is important to understand that blue light in and of itself is not the problem, as it is everywhere and the main source of it is sunlight. Looking at a computer screen is, “trivial compared to me walking outside and looking up at the sky – not at the sun, just the sky” explains Dr. John O’Hagan of Public Health England’s center for radiation, chemical, and environmental hazards. If blue light was harmful to us, we’d be aware of it long before screens dominated our lives. According to experts such as O’Hagan, the cause for concern is not the light itself, but the fact that it governs our circadian rhythms, the natural sleep-wake cycles that repeat roughly every 24 hours. 

We no longer go to bed with sundown, like our hunter-gatherer forefathers used to. We check social media and our bank balance, grapple with work using laptops and computers, not to mention watch TV long after the sun has set. We are exposed to significant amounts of blue light that impede sleep and disrupt circadian rhythms. 

A lot of the research about nighttime exposure to light is preliminary, but a recent study conducted in Harvard outlined the sometimes indirect connections between exposure to light and lower energy levels, mental health, and even heightened risk of cancer: the effect of blue light on the secretion of melatonin, a hormone with significant influence over the natural circadian rhythm. To test this theory, the Harvard researchers compared the effect of 6.5 hours of exposure to blue light to green light of equal brightness. When testing the melatonin levels of the participants it was found that the blue light suppressed melatonin for about twice as long as the green light and shifted circadian rhythms by twice as much - 3 hours vs. 1.5 hours.

Another study, conducted in the University of Toronto, compared the melatonin levels of people exposed to bright indoor light who were wearing blue-light-blocking goggles to people exposed to regular dim light without wearing goggles. The hormone levels were about the same in the two groups, which indicates that blue light is a potent suppressor of melatonin.

When our body doesn’t produce sufficient levels of melatonin, we are exposed to all of the health risks of sleep deprivation - weakened immune system, trouble concentrating, high blood pressure, risk of heart disease, and more.

Related Article: Important Things to Know About Stress-Related Sleep Issues

There are a few measures you can take to minimize your exposure to blue light in order to better your sleep routine. 

• Use dim warm lights for night lights. Warm light, like red and yellow, has the least power to shift circadian rhythm and suppress melatonin.
• Avoid looking at bright screens beginning about two to three hours before bed.
• If you must be exposed to light at night, because you work a night shift, for example, consider wearing blue-blocking glasses or installing an app that filters the blue/green wavelength at night.
• Expose yourself to a lot of natural bright light during the day, which will help your ability to sleep at night, as well as your mood and alertness during the day. Experts stress that it is important to go outside during lunchtime, when the light is particularly bright, rather than dusk.