Blue light exposure may increase the risk of a number of problems, including macular degeneration and depression. Our modern world is flooded with artificial light. We over illuminate our homes and workplaces, bright streetlights are everywhere and we spend more time on our mobile devices than ever. The development of artificial light allowed us to work longer, sleep later and facilitates our 24 hour entertainment culture.

Recent research has found significant shortcomings with our current approach to lighting. Several studies have demonstrated that the blue light wavelengths emitted by most bulbs and electronic devices can be hazardous to our health.

Research in blue light and its effects on sleep and depression are in their infancy. However, initials reports indicate that blue light from objects such as computers and cell phones can affect sleep and aggravate the symptoms of depression.

Over the course of millions of years of evolution our bodies have been tuned to the rhythms of the sun. Until the advent of artificial lighting, the sun was our major source of lighting and we spent most of the evening hours in relative darkness. Now, in much of the world our lives are illuminated at all hours of the day and night.

It turns out that being exposed to too much light at night throws off the body’s biological clock. When our circadian rhythms are disrupted, our sleep suffers. In addition, research has suggested it can contribute to a risk of cancer, diabetes, heart disease, and obesity. Because all these health conditions are associated with depression, scientists are concerned that blue light may also affect mood.

Not all colors of light have the same effect on our mood. The bluerich light of the morning sun inhibits the release of the sleep hormone melatonin. It also triggers the production of hormones like cortisol and ghrelin, which make us hungry and alert.

Blue wavelengths are beneficial during daylight hours because they boost attention, reaction times and mood. However, they are disruptive at night. Electronics with screens, as well as energy-efficient lighting, have increased our exposure to blue wavelengths. This is especially problematic after sundown when our bodies need to be exposed to less light in order to keep our circadian rhythms in check.

Everyone has slightly different circadian rhythms, but the average length is 24 and one-quarter hours. The circadian rhythms of people who stay up late is slightly longer, while the rhythms of early risers fall short of 24 hours. Another problem with blue light is its ability to damage our eyes. A study by the University of Toledo found that blue light triggers the creation of poisonous molecules in photoreceptor cells of the retinas. These molecules can speed up sight degeneration.

Research has suggested an association between exposure to light at night, such as working night shifts, to some types of cancer, diabetes, heart disease, and obesity. This may be partially due to the fact that exposure to light suppresses the secretion of melatonin, a hormone that influences circadian rhythms.

Even dim light can interfere with a person’s circadian rhythms and melatonin secretion. Around eight lux is a level of brightness exceeded by most table lamps and about twice that of a night light. Even at this low level circadian rhythms can be disturbed.

According to research, exposure to blue light is part of the reason so many people don’t get enough sleep. Studies have linked short sleep to increased risk for depression as well as diabetes and cardiovascular problems.

While any kind of light suppresses the secretion of melatonin, blue light at night does it more strongly. In 2003, Harvard researchers conducted a study comparing the effects of 6.5 hours of exposure to blue light to exposure to green light of comparable brightness. The blue light suppressed melatonin for twice as long as the green light and shifted circadian rhythms by twice as much (3 hours vs. 1.5 hours).

Our use of electronic devices does not appear to be lessening. A study by the American Psychological Association (APA) reported that 86% of adults in the U.S. said they “constantly or often” check their emails, texts and social media accounts. The “constant checkers” had higher stress levels than those who did not engage with technology as frequently. On a 10-point scale, where 1 was “little or no stress” and 10 was “a great deal of stress,” the average reported overall stress level of constant checkers was 5.3. For non-constant checkers, the average reported stress level was 4.4.

There’s also such a thing as “computer vision syndrome,” also referred to as “digital eye strain.” It describes a group of eye and vision-related problems that result from prolonged computer, tablet, e-reader and cell phone use. Virtually all of these types of devices emit blue light. Many individuals experience severe eye discomfort and vision problems when viewing digital screens for extended periods. Research estimates suggest its prevalence may be 50% or more among computer users.

In a Canadian study of blue light, researchers compared the melatonin levels of people exposed to bright indoor light who were wearing bluelight–blocking glasses to people exposed to regular dim light without wearing the glasses. The levels of the hormone were about the same in the two groups suggesting that blue light is a potent suppressor of melatonin. It also indicates that people can protect themselves by wearing eyewear that blocks blue light.

Glasses with a lens coating that blocks out blue light start at around $100. However, there’s a newer technology that actually injects the blue light filtering into the lens rather than just coating it. There’s some evidence that having the blue blocking inside the lens filters out more of the blue light. There are other ways to protect yourself from blue light at night. For one, use dim red lights for night lights. Red light has the least power to shift circadian rhythm and suppress melatonin. In addition, avoid looking at bright screens beginning two to three hours before bed.

If you use a lot of electronic devices at night or even stay up late, consider wearing blue-blocking glasses or installing an app that filters the blue/green wavelength at night. Similarly, some televisions now have settings so you can turn off the blue light.

Another thing that helps is exposing yourself to bright light during the day time. It increases your ability to sleep at night and can improve mood and alertness during the day. In fact, bright light during the day can have similar effects as light therapy in that it may reduce feelings of depression.

Randi Fredricks, Ph.D.


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