Long Term Side Effects Of Blue Light That Aren't Widely Discussed

You probably don't need to be told that doom-scrolling late at night is not good for your health. Largely, the adverse effects associated with this behavior are linked to blue light exposure. While not inherently a bad thing, the amount and time that you are exposed to blue light can have problematic outcomes and affect many different aspects of your health that you might not have previously considered. For instance, blue light exposure can impact vision, sleep, cardiovascular function, and even increase the risk of some cancers. In other words, it is not something to be taken lightly.

We encounter blue light regularly. The main source of blue light is the sun. We perceive colors based on their visible light waves, and blue is on the smaller wavelength end of the spectrum, ranging from 380 to 500 nanometers. Given how we calculate energy with wavelength, these shorter wavelengths mean that light on this end of the spectrum is also higher energy. Exposure to this natural light is important for our brains and sleep-wake cycles, and those cycles have largely been tuned to the sun. However, we now encounter blue light frequently from LED and fluorescent lights, as well as electronic devices, like phones and computers. The long-term effects of these differential exposures is an ongoing research topic, and some concerning results have emerged over the years.

As mentioned above, there are some benefits to blue light, depending on the amount and timing of exposure. Our body works on a schedule known as the circadian rhythm. Because we are diurnal (as opposed to nocturnal), our bodily systems work to optimize wakefulness in the daytime and sleep during the night. As such, our internal clocks are set by light exposure, which is one reason you should never sleep with the light on. Blue light induces wakefulness and causes the body to decrease melatonin production. So, staring at your screen at 2 p.m., when the sun is out and shining, is not necessarily problematic. Where we start to see long-term effects is when blue light exposure occurs in the evening and at night.

Many of these trends have been noted in people who work the night shift. A repeated association has been established between exposure to artificial light at night — particularly within the blue emitting wave lengths — and cancer risk. For instance, research indicates that night-shift workers are more likely to develop breast cancer or prostate cancer when they work under outdoor artificial light at night, especially when this light is within the blue spectrum. While an exact mechanism is unknown, other studies have demonstrated that melatonin suppression is associated with cancer risk, and we know that blue light reduces melatonin production. Additional studies have shown that blue light causes oxidative stress and DNA damage, two things that also increase the risk of cancer.

Much of the blue light we are exposed to at night comes from artificial lights, such as electronic devices. However, when used at the right time of day, this source of blue light does not necessarily have a damaging effect, as the intensity of light we get from these devices in the daytime is significantly less than that from the sun. That being said, the level of blue light we are exposed to by the sun can induce its own damage.

Light is filtered through the cornea and lens in our eyes. Perhaps surprisingly, those structures are actually pretty good at filtering out ultraviolet light. However, they are not great at filtering out visible blue light. Some studies have shown that blue light causes damage to retinal cells. This damaging level of intensity is easily garnered from the sun or by staring directly into a bright LED light.

But most of us know to put on sunglasses when the sun is bright and to avoid staring directly into bright lights. The harder thing to avoid might be the blue light from staring at our screens all day. Well, there is some good and bad news. As of now, no human studies have demonstrated that the blue light exposure from staring at your screen for a long time directly causes eye damage. However, these studies have not been performed longitudinally, emphasizing the need for more studies to fully understand the impact that long-term blue light will have.