Most people are unaware of the fact that bright light after sunset probably isn’t healthy, especially if you are suffering from insomnia, dealing with poor sleep quality, or a circadian rhythm disorder. For millions of years, humans functioned without artificial lights, TVs, and other electronics (e.g. cell phone screens). They relied solely on the sunlight and their circadian rhythms adjusted; making it easy to rise with the sun and sleep after sunset.
In the age of technology, our senses are bombarded with bright street lights, household lights, TVs, computers, and cell phone screens long after the sun has set. The problem is that bright light from these sources after sunset stimulates your retina and tricks your brain into thinking it’s still daytime. You may know consciously that it’s “night” but this is an unconscious process – interpreted by your nervous system as the sun being high in the sky.
The excessive light stimulation after sunset triggers a cascade of neurophysiological changes that will detrimentally impact your mental and physical health – even if you aren’t perceptive of these effects. Although all light after sunset is problematic, perhaps the most problematic wavelength is that of “blue light.” Blue light exposure after dusk has been associated with causing insomnia and sleep disorders, but also more serious illnesses like cancer, heart disease, diabetes and obesity.
What is blue light?
Light consists of electromagnetic particles that travel in “waves.” The waves vary in terms of length and intensity. The shorter the “wavelength” of light, the greater the concentration of energy. The length of the light waves is measured in nanometers (nm) and each wavelength is associated with a particular color. All light is categorized into either: gamma rays, x-rays, UV (ultraviolet) rays, visible light, infrared light, and radio waves.
The eyes of humans are only sensitive to the wavelength of “visible light.” All visible light contains colors of: red, orange, yellow, green, blue, indigo, and violet. Within the visible light spectrum, blue light has a very short wavelength (380 nm to 500 nm) and is ultimately more intense to the eye. The effect of blue light can be positive or negative depending on the time of day exposed.
Individuals exposed to blue light during the day generally are in a better mood, have more energy, and are more alert. However, exposure to blue light after the sun has set will suppress melatonin production and increase your risk of insomnia, poor sleep, and even more serious conditions like cancer. Therefore it is likely important to be cognizant of your blue light exposure and remember – it’s good during the day, but bad at night.
What are the sources of blue light?
Blue light is ubiquitous in that it is nearly everywhere. As light from the sun penetrates the atmosphere, short/high-intensity blue wavelengths of the spectrum collide with air molecules. This collision results in the scattering of blue light in all directions (everywhere you look). Blue light is what causes us to perceive the sky as having a “blue color.”
Despite the fact that it is produced naturally by the sun, blue light is also artificially generated from technology – particularly digital screens. If you use a TV, computer, smart phone, iPad, or other electronic device – you’ve been exposed to blue light. The light bulbs in your house emit blue wavelengths unless you’ve strategically replaced them; perhaps the worst culprits for excessive blue light generation are fluorescent bulbs and LEDs.
How Nighttime Blue Light Exposure Disrupts Sleep, Causes Insomnia
When the sun sets, your body responds to the darkness by changing its hormone production to reduce arousal and promote somnolence. Most notably is a shift in the production of the neurohormone melatonin, which is secreted by an organ in the brain called the pineal gland. The pineal gland begins manufacturing melatonin several hours before you go to bed; as the melatonin levels continue to rise, you feel sleepier.
Think of melatonin as an endogenously produced sleep-promoting agent. It doesn’t knock you out like a sleeping pill, but makes it easier to fall asleep when it is sufficiently produced. In other words, your alertness drops, you feel drowsier, and it becomes more difficult to resist falling asleep.
Blue light prevents release of melatonin from the pineal gland
Blue light exposure is known to prevent endogenous release of melatonin from the pineal gland. Thus you’re left with no melatonin to facilitate sleepiness. Melatonin has a number of other functions such as: acting as a neuroprotective agent and influencing production of serotonin. Individuals with low serotonin often also have low levels of melatonin; the two tend to have a symbiotic relationship.
While a little bit of blue light may not significantly alter melatonin production, when a certain threshold is met (in terms of the amount contacting the eye), the pineal gland doesn’t release melatonin. If you’ve been hopping into bed with your iPad, cell phone, laptop, or even watching late night TV – you’re disrupting your body’s ability to produce melatonin.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/21193540
- Source: http://www.ncbi.nlm.nih.gov/pubmed/21552190
Cascade effects stemming from melatonin disruption
Melatonin disruption may not seem like a big deal, but it really disrupts your entire physiology. Disruption in the endogenous production of melatonin is capable of triggering a cascade effect – altering other hormones, neurotransmitters, and your circadian rhythm. Deficient melatonin at night has been linked to a variety of serious health conditions such as: cancer, diabetes, and heart disease.
Arousal: Melatonin production reduces your arousal, thus allowing you to fall asleep. Individuals with high arousal or subject to significant stress aren’t able to manufacture necessary melatonin to tone down their sympathetic nervous system. If you’re exposed to blue light at night, you are more likely to maintain a higher degree of physiological arousal, or perhaps exacerbate preexisting stress.
Circadian rhythm disorders: In the past, humans never had circadian rhythm disorders due to the fact that they relied solely on the sun for light. When melatonin production is disrupted by exposure to blue light at night, people develop conditions like shift work sleep disorder; characterized by sleep-wake cycle abnormalities. Blue light disrupts the body’s natural “biological clock” or inclination to wake and sleep at certain times – which leads to compromised psychological health.
Insomnia: Most individuals with insomnia are unaware of the fact that bright light – particularly blue light is impeding their ability to fall asleep. Melatonin is a hormone necessary to help promote somnolence. Some cases of insomnia are likely caused by significant exposure to blue light prior to bed.
Neurotransmission: Melatonin has a symbiotic relationship with many other neurotransmitters such as serotonin. When one or the other becomes imbalanced, the other may also become imbalanced. This may create an endogenous chemical imbalance, which may increase your risk of developing mood disorders like depression.
Sleep quality: Lack of melatonin tends to decrease a person’s sleep quality. The body has unconscious physiological processes taking place that help promote health and survival. If these processes (e.g. melatonin production) are disrupted by blue light, it will impair the time you spend in deep, restorative sleep. An easy way to compromise sleep quality is to inhibit production of melatonin.
Other health risks: There are an array of general health risks associated with inadequate melatonin production at night. Since blue light is known to inhibit the release of melatonin, exposing yourself to blue light may be upping your odds of developing an unwanted health condition.
- Cancer: If you’re exposed to light at night, you may be increasing your risk of developing cancer (both breast cancer and prostate cancer). Low melatonin levels at night are thought to increase risk of developing many different types of cancer. Adequate levels are hypothesized to have anticancer properties.
- Diabetes: Exposure to blue light before bed may also facilitate the development of diabetes. As your circadian rhythms become disrupted, your blood sugar levels skyrocket and may throw you into a “prediabetic” state. Consistently disrupted blood sugar levels may result in a permanent diagnosis of Type 2 diabetes.
- Immune system impairment: When neurohormone production is altered as a result of light exposure after sunset, your immune system becomes impaired. This may leave you to get sick more often than others with proper melatonin production and sufficient sleep.
- Obesity: Those exposed to blue light at night are known to experience a disrupt in circadian rhythms. The circadian rhythm disruption has been associated with decreases in the hormone “leptin.” After you eat, your leptin levels are high which make you feel “full.” Decreased leptin from circadian rhythm disruptions make you feel less full and more likely to eat in excess.
Source: http://www.ncbi.nlm.nih.gov/pubmed/19095474
Source: http://www.ncbi.nlm.nih.gov/pubmed/20536686
To what extent does blue light affect the circadian rhythm and melatonin?
It should be clear that any light exposure after sunset will suppress melatonin secretion. That said, some wavelengths like blue light have a significantly greater effect than others. In a study conducted by Harvard, researchers compared nearly 7 hours of blue light exposure to green light; both were considered equally bright. Blue light exposure suppressed melatonin secretion nearly two-fold compared to green light exposure.
In other words, blue light has nearly twice as potent of an effect on your circadian rhythm compared to green light. This means that if green light exposure postponed your ability to fall asleep by 2 hours, blue light would postpone it by 4 hours. Other research is in congruence with the findings by those at Harvard.
A study by researchers at University of Toronto compared melatonin levels of individuals wearing blue-blocking goggles (to block indoor light) to individuals exposed to standard dim light with no goggles. Researchers found that melatonin levels were nearly equivalent in both groups. This showed that by simply blocking out blue light by wearing filtered goggles, melatonin levels were nearly the same as someone without exposure to any significant bright light.
Other studies have shown that approximately 60 minutes of general bright light exposure (1000 lux) at night suppressed melatonin to daytime levels. Although eliminating all light is a healthy idea after sunset, this isn’t realistic for most people. Instead, it may be better to compromise and implement the Pareto principle – target the wavelength with the greatest impact (blue light) on melatonin suppression.
How To Block Blue Light for Better Sleep
There are millions of people suffering from insomnia, but very few people making calculated efforts to overcome it. Rather than waiting for new sleeping pills to hit the market, you may just need to eliminate blue light exposure after sunset. Below are some ways you can block blue light to improve sleep quality and reduce the likelihood of insomnia without taking dangerous psychiatric drugs the like current Z-drugs linked to dementia.
1. Blue light blocking glasses/goggles
One effective way to limit your blue light exposure after sunset is to invest in some blue-blocking goggles or glasses. You can pick up a pair for less than $20, or if you want to get a bit stylish you can spend a little more money. Goggles may do a better job of blocking out light from all angles including the periphery when compared to sunglasses.
That said, sunglasses are still highly effective compared to no intervention at all. Anyone that’s going to be looking at a laptop, playing on an iPad, using a cell phone, or watching TV at night should be wearing blue light blocking glasses for the sake of their health.
2. Tweak your lighting
If you’ve customized the lights in your home to change based on the time of day, you’re one step ahead of the game. Specifically, you should focus on implementing either dim lights, red lights, or dim red lights. The tertiary option is likely superior to the first two, but all options are better than standard bright lights (especially LEDs and fluorescents).
- Dim lights: If your lights can be dimmed, you should use the dimmed setting. The dimmer the light, the less your melatonin will be disrupted by the brightness. Use the dimmest setting after the sun has set.
- Red lights: Some people have strategically installed red lights throughout their home to minimize exposure to blue light after dark. Red lights don’t have as significant of an impact on your body’s circadian rhythm as other wavelengths.
- Dim red lights: Those that are knowledgeable of the effects of light on neurohormone production may be futuristic compared to others in that they’ve installed dim red lights in their home. These lights can be used for visibility after the sun has set, yet they are the least likely to disrupt hormone (melatonin) production.
If you want to use nightlights such as to help you navigate to the bathroom during the middle of the night, it would be best to install dim red lights. These will provide visibility, yet won’t impair your ability to fall back asleep. You don’t want to jolt your retinas with a bright light of any kind if you wake up during the middle of the night; this will trick your physiology into thinking that it’s daytime.
3. Screen filters
If you don’t already have blue light blocking glasses or goggles, you’ll want to filter the screens of all digital, electronic devices. A general rule of thumb for those with insomnia is to avoid looking at bright screens 2 to 3 hours before bed. If you need to look at a screen, you may want to have a filter for it.
- F.lux: If you’re using a computer, you should download the program “F.lux.” It’s a free program that filters your computer screen based on the rising and setting of the sun. After sunset, the program filters out all blue light and doesn’t interfere with your endogenous production of melatonin.
It still boggles my mind as to why TVs, smartphones, and tablets aren’t manufactured with this screen-filtering technology (or at least the option). Screen filters reduce blue light, while still allowing you to use the device. Although they will not eliminate Wi-Fi exposure (which could cause insomnia), they will not significantly decrease melatonin production.
Bottom line: Daytime blue light is good, nighttime blue light is bad
Just because blue light exposure at night has a detrimental effect on health, lack of blue light exposure during the day may be just as bad. During the daytime (when the sun is up), blue light exposure promotes wakefulness, vigor, and vigilance. If you want to be energized and want optimal mental performance throughout the day, blue light is necessary.
Your pineal gland doesn’t need to produce sleep-promoting melatonin during the day. Blocking blue light during the day may increase your risk of developing depression or fatigue. In fact, those suffering from certain types of depression (e.g. seasonal affective disorder) often benefit from customized “blue light” boxes that produce potent blue light during the daytime.
After sunset, you should be using the aforementioned tactics to minimize blue light exposure such as: screen filters, customized lighting, and blue blocker glasses. Your goal should be to optimize your circadian rhythm and prevent exogenous light sources (e.g. from cell phones) from adversely affecting both your physical and mental health. If you want to improve your sleep quality or overcome insomnia – minimizing blue light exposure at night should be a priority.
Have you blocked blue light to improve sleep quality?
If you’ve strategically blocked out blue light to improve your sleep quality and reduced insomnia, feel free to share a comment mentioning whether you noticed any benefit and how quickly you noticed improvement in your sleep. The science supports the idea that filtering out blue light is likely to benefit many people struggling with insomnia and other circadian rhythm disorders. If you have filtered out blue light during the night, what methods do you use (e.g. sunglasses, filters, customized lighting, etc.)?
I very sensitive to light when I sleep. I wake up if the full moon is shining in the window at all and use blackout curtains. I recently noticed my sleep was getting worse, to the point of not really sleeping at all. I also noticed that they changed the Sodium lights in my neighborhood to LED lights at almost the precise time this bout of insomnia started.