Celebrities of a certain age are often seen sporting amber colored, blue light blocking glasses. Many celebrity gossip magazines sarcastically speculate that these aging celebs probably need regular glasses but are trying to look cool by wearing blue-blocking prescription lenses.
I guess that it would be hard to maintain the reputation of being a rock and roll legend while wearing bifocals.
It still begs the question about what the deal is with blue blocking glasses anyway.
Blue-blocking glasses are touted as having a myriad of health benefits. Probably, the most common reason for using blue blocking glasses is sleep promotion. It seems that we are in the middle of a pandemic of insomnia. People who are desperate for a decent nights sleep will happily try almost anything to avoid the 'witching hour' (as Roald Dahl called it).
Let's see if blue blocking glasses work (and if so, for what conditions) or are they just another celebrity fad?
What Are Blue Light Blocking Glasses?
In high school biology, we learned about the effects of light on rods and cones in the retina to help us see but that was about it for light and the eye.
We now know that the secret life of the retina is much more complex than that.
Light affects us both visually and non-visually.
Visual light helps us to see and non-visual light plays a key role in our circadian rhythm (now called circadian entrainment), melatonin regulation, cognitive performance, memory, and body temperature.
Circadian rhythms are physical, mental, and behavioral changes that follow a daily cycle.
The circadian rhythm is maintained by external cues known as zeitgebers. (I just love that word). A zeitgeber is any external or environmental cue that entrains or synchronizes our biological rhythms to the light/dark cycle. Common zeitgebers are food, exercise, temperature, and light.
The visible spectrum of light goes from 360 to 720nm and sits between ultraviolet and infrared radiation. Visible light is referred to as short (blue), medium (green) and long (red) radiation. Blue light begins at 380 nm and ends at 500nm and has high photon energy.
Blue light-sensitive receptors in the retina signal to the brain that it is daytime and thereby control the circadian rhythm.
The exact detail of how this complex physiological system works is as follows.
The blue light triggers a photopigment called melanopsin in the retina. Melanopsin absorbs lightwaves with a peak absorption of 460 to 480 nm. The melanopsin then communicates with specialized nerve cells in the retina which are called intrinsically photoreceptive retinal ganglion cells (ipRGC). Hang in there, this nerdy science is relevant.
The ipRGC communicates whether it is day/night to the brain. This happens when the ipRGC communicates with the suprachiasmatic nucleus (the conductor of the circadian rhythm) which in turn communicates with the pineal gland. The pineal gland produces melatonin at night and switches it off by day. Melatonin helps us sleep and has been said to 'open the sleep gate'.
But it is even more complex than that. The ipRGC network also communicates with other key areas of the brain such as the limbic system, the striatum, and the brain stem.
If blue light exposure reduces or delays melatonin release, then this could affect the onset of sleep.
As the eye ages, less blue light enters the eye which can affect the circadian rhythm in this population demographic.
Blue light is found in natural light and is also emitted from a wide range of devices that are commonly used in most households e.g. light emitting diodes (LEDs) lights, LED devices, smartphones, and e-books. LEDs are growing in popularity and are promoted as part of the Kyoto Protocol as they reduce energy consumption.
It is currently predicted that LED lights will replace incandescent bulbs and fluorescent lamps in many parts of the globe in the near future. Most of my friends' houses have already made that transition.
There are over 7000 blue blocking devices for sale on Amazon. Blue-blocking glasses range in price from $7 to $170.
Blue-blocking devices extend way beyond glasses and physical products. There are apps (isn't there an app for everything now?) that can change the intensity of blue light from phones and computers.
The issue of blue-blocking has not escaped the leading manufacturers of bulbs. Both Philips and General Electric are researching ways to modify the blue light emissions from their bulbs.
I am going to go out on a limb here and make a wild guess. Looking at the complexity of the physiology of blue light, I am going to predict that the clinical effects of blue-blocking glasses cannot be summarized in a 140 character tweet. What does the research say?
Is There Any Research?
There are 793 publications relating to blue blocking glasses which include just 19 clinical trials. Let's compare this to another light blocker like sunscreen which has 6796 publications and 439 clinical trials.
I had never heard of the journal 'Chronobiology International' until I began to research this topic. Chronobiology refers to biological rhythms and cycles such as the circadian rhythm and this journal hosts many of the studies published on blue blocking glasses. It is officially my new favorite journal because it has such a cool name. What's not to love about the words zeitgebers and chronobiology?
Does Wearing Them Improve Sleep?
As mentioned above, blue light is intricately connected with our sleep/wake cycle.
A 2017 meta-analysis of blue-blocking glasses on the sleep-wake cycle identified only 3 studies with 136 participants and concluded that there was a lack of high-quality evidence to support the use of these glasses for insomnia (13). Doing a meta-analysis is a huge amount of work.
Even if only three studies are eventually analyzed, a ton of work goes into finding and eliminating non-relevant studies.
Question. What is the worst thing that can happen to a team doing a meta-analysis?
Answer. How about the meta-analysis being published at almost the exact same time that a new and well-designed relevant study hits the journals? Ouch. That essentially makes the meta-analysis null and void and out of date. That is exactly what happened to the group who published their meta-analysis in Q4 2017.
A randomized controlled trial published this year looked at blue blocking glasses for insomnia symptoms (14). The team from Colombia University assessed the effect of blocking nocturnal blue light for 2 hours before bed for seven consecutive nights in 14 study subjects with insomnia symptoms. This was a cross-over trial design and the subjects wore lightweight clear glasses or blue blocking glasses in a randomized order.
The study found a statistically significant improvement in quality, quantity, and soundness of sleep with the blue blocking glasses. The authors noted that a limitation of the study was their failure to measure actual melatonin levels and they recommend that future studies should include measurement of 6-sulfatoxymelatonin (as a surrogate measure of melatonin in the blood).
One of the key target groups for blue blocking glasses is shift workers. These workers are invariably exposed to light on their commute home which can activate the day cycle in their circadian rhythm. Having worked nights in the ER, I can attest to that. Tossing and turning all day, while dreading going back to work when exhausted is pretty awful.
In this study, eight permanent shift workers in Quebec's post center wore blue blocking glasses for two weeks (15). Each study participant had baseline data collected and acted as their own controls. Wrist activity monitors and subject records were monitored. The blue blocking glasses increased sleep efficacy and decreased sleep fragmentation.
Another related study (though looking at staying awake) was published in 2015 and looked at the effect of blue light aids in preventing the post-lunch dip (16). The study used electroencephalogram (EEG) and assessment of performance. The healthy volunteers were tested under four different conditions: dark, 33% blue light, 66% blue light and white light.
The study found that blue light reduced the EEG changes that are associated with sleep and increased performance. The authors concluded that this was a possible 'chronobiological ergonomic' solution. Call it what you like, I know a few people at work who could do with a daily infusion of blue light daily or 'chronobiological ergonomic' solution.
Blue light has been shown to improve sleep during the polar winters where people would normally have no exposure to natural light (17).
Despite a negative meta-analysis, I think that there is some connection between blue blockers and sleep promotion in select groups, though further work is needed to fully understand this.
Does Exposure to Blue Light Reduce Melatonin?
There are two key studies which show that blue light exposure reduces melatonin secretion.
The first study showed that a five-hour evening exposure to a LED-backlit computer versus a non LED-backlit computer reduced melatonin and feelings of sleepiness (1). This was a Swiss study in 13 young male volunteers under controlled laboratory conditions in a balanced crossover design.
The second study showed that reading a LED-eBook took longer to fall asleep and reduced evening sleepiness, melatonin secretion and reduced next-morning alertness as compared to reading a printed book (2). I hate to say I told you so, but I totally figured this one out from personal experience.
A total of 12 study participants were involved in the study which was a 14 day crossover study involving 5 days of reading a LED-ebook and 5 days of a print book.
There were two requirements regarding reading material in either electronic or printed form: (i) it had to consist of printed text on the page (no pictures, illustrations, graphic novels, magazines, puzzles, etc.); and (ii) it had to be considered “pleasure” or “leisure” reading (no textbooks, reference books, or coursework). Such a great study and study design.
French Canadian researchers conducted a study in 2006 which conclusively showed that wearing blue-blocking glasses can prevent light-induced reductions in melatonin levels (3). The impetus for the study came from an interest in finding a way that night workers could use light blocking glasses on their commute home so that they could still drive safely and yet be able to sleep once they reached home.
The study was small and had just 14 participants. The study participants were exposed at night to a 60 min bright light pulse between 01:00 and 02:00 hours while wearing orange lens glasses or grey lens glasses. Salivary melatonin change observed during the light pulse was compared with a melatonin baseline obtained the night before.
A non-significant increase in melatonin levels of 6% was observed with the orange lens whereas a significant (P < 0.05) reduction of 46% was observed with the grey lens.
A 2016 study in the journal 'Chronobiology International' showed that the onset of melatonin rise occurred earlier in 9 patients when they were wearing blue-blocking glasses at night (4).
Two weeks of using blue blocking glasses were shown to reduce attenuated LED-induced melatonin suppression in the evening and decreased vigilant attention and subjective alertness before bedtime in 13 teenage boys (5).
A hodge-podge of studies suggests that melatonin levels drop as exposure to blue light increases.
Does Exposure To Blue Light Increase Cancer Risk?
Lack of melatonin has been linked to an increased risk of cancer, especially breast, ovarian and prostate cancer. Hence the growing focus on ensuring that people have adequate sleep.
The best data on the risks of blue light and cancer comes from long-term follow up of children who were exposed to blue light therapy as neonates to help them recover from neonatal jaundice The blue light helps the immature livers of these young babies deal with the high levels of bilirubin.
There was some concern in the medical literature that these children had a higher risk of developing certain types of skin cancers. A 2106 meta-analysis showed that there was no connection between blue light exposure as a baby and subsequent development of skin cancers known as melanotic naevi (6).
As mentioned above, light exposure reduces melatonin levels. As blue blocking glasses promote melatonin production, it has been hypothesized that blue blocking glasses could reduce the risk of cancer. A commentary paper on the topic concludes that 'chronodisruption' by blue light blocking is unlikely to be effective on its own as a cancer prevention strategy (7). I agree.
There may well be some sort of a connection between blue light and the triad of sleep, melatonin, and cancer but it is currently just speculation at this time.
Does Exposure To Blue Light Increase Risk of Heart Disease or Diabetes?
The only links between diabetes and blue light that I could find related to the use of blue laser theory in diabetic retinopathy.
Equally, there is very limited data on blue light and heart disease. A study in 20 healthy subjects showed that oscillating red, green and blue light optimized autonomic cardiac function. (8)
Blue-blocking glasses were found to reduce systolic and diastolic blood pressure one-month post surgery in 1367 patients who had implantation of blue-blocking lenses during cataract surgery (9).
There are no proven links between heart disease or diabetes and blue light.
Does Wearing Blue Light Blocking Glasses Protect The Eyes?
A 2015 study in mice showed that blue light exposure increased reactive oxygen species and inflammatory cytokines (10).
An earlier 2014 study in murine cells also showed that blue LED light increased reactive oxygen species (ROS) production, altered the protein expression level, induced the aggregation of short-wavelength opsins (S-opsin), resulting in severe cell damage (11).
The majority of the research on blue light and the eyes relates to the issue of the aging eye and cataracts.
Cataracts account for 50% of blindness worldwide. Cataracts reduce the amount of light entering the eye and as such could theoretically impair the circadian rhythm. Cataract removal and intraocular lens placement is a very popular surgery nowadays and is usually done as a day case under local anesthetic.
The surgery removes the cataract which improves the visual acuity but also increases the amount of light entering the eye. This includes the amount of blue light.
A 2014 study investigated sleep patterns before and after cataract surgery (12). They used the standard questionnaire for sleep which is the Pittsburgh Sleep Quality Index. The questionnaire was administered to 961 patients who were undergoing cataract surgery.
These patients either had a UVB blocking clear lens or a lens with a blue filter inserted during the surgery. Interestingly (aka I did not know this before) blue blocking intra-ocular lenses were developed to improve contrast sensitivity and to reduce the blue hue that patients report after cataract surgery.
Prior to the study, 50% of the study participants reported poor sleep. The study excluded people with a history of drug use, alcohol dependence, head injuries or psychiatric diagnoses. The researchers even accounted for the season on which the surgery was done.
Cataract surgery and lens placement improved the quality of sleep in both the clear and blue lens filtering arms of the study and this was maintained for 6 months.
However, this benefit was lost at 12 months. The authors tried to explain this change in sleep pattern over time and put forward two possible explanations:
1. The initial improvement in sleep might be due to fatigue as people with newly improved vision tend to be more physically active or
2. Habituation of the circadian rhythm to the extra light over time.
There is no human-derived evidence to support a role for blue light blockers in 'protecting' the eye.
Does Wearing Them Reduce Cortisol?
Some bloggers have claimed that wearing blue-blocking glasses has helped them reduce their cortisol levels which they assessed by using some home kit for cortisol measurement.
There are no studies directly showing that blue blocking glasses reduce cortisol but there is some biological plausibility that it could be true.
This comes from a mishmash of data. Functional MRI studies show that blue light activates the locus coeruleus in the brain (18). The locus coeruleus activates the hypothalamic-pituitary-adrenal access which makes cortisol. So we have biological plausibility possibly.
A study investigated changes in serum melatonin levels, cortisol levels, body temperature, and psychiatric measures with a randomized, double-blind, cross-over, placebo-controlled design (19). The study subjects played smartphone games with either conventional LED or suppressed blue light from 7:30 to 10:00 PM. Then, they were readmitted and conducted the same procedure with the other type of smartphone.
Users of blue LED smartphones experienced a longer time to reach dim light melatonin onset and had increases in body temperature, serum melatonin levels, and cortisol levels, although these changes were not statistically significant.
Blue light prevented a confinement-induced rise in cortisol levels in the Nile tilapia fish (20).
There is no conclusive scientific evidence to link blue blocking glasses to reduced cortisol levels.
Does Wearing Them Improve Mood?
Norwegian and US-based investigators addressed the effectiveness of blue-blocking glasses in patients with mania (21). Manic episodes have some (as yet ill-understood) relationship with the light/dark cycles and seasons. Darkroom therapy has been used with some success in manic patients but this seems like a rather extreme form of sensory deprivation. Could blue blocking glasses help these patients was the question posed by the study team?
This was a single-blinded, randomized, placebo-controlled trial in 32 Norwegian patients. Study participants were randomized to wear either blue blocking glasses or regular clear glasses from 6 pm to 8 am for seven days. In view of the seriousness of a diagnosis of mania, patients also received whatever their standard treatment would have been at this time.
A statistically significant difference in the mania score was noted between the blue-blocking glasses and the placebo glasses group. Interestingly, some of the symptoms of mania were reduced within one night of wearing the glasses.
Blue-blocking glasses may help with symptoms of mania.
Do They Help With Cognitive Function In Ageing?
A 2013 Canadian study used functional fMRI to record the effect of light on task-related brain responses in young and older participants (22). They found that while older people retained an ability to have a sustained response to light in many areas of the brain, that the effect of blue light on the brain is decreased in areas that are related to alertness and higher executive processing tasks like multi-tasking or focused attention (amygdala, pulvinar, tegmentum).
Blue light responsiveness in key areas related to executive functioning in the brain changes with aging.
Are There Other Types of Light Therapy?
A fascinating study in my new favorite journal 'Chronobiology International' studied the effects of blue light, dawn-simulating light and polychromatic light in 17 participants who had restricted sleep schedules (23). Each study participant experienced each of the light options for two nights. There was a wash-out period of two weeks between each light exposure.
The investigators found that subjective well-being, mood, and cognitive functioning was improved in the conditions of dawn simulated light as compared to daylight or blue light. This prompted the researchers to suggest that daylight simulated light might be an effective strategy for enhancing cognitive functioning under conditions of mild sleep deprivation.
Are Blue Light Blocking Glasses Safe?
Generally speaking, blue blocking glasses are safe. Some users in studies reported headaches. The investigators wondered if the headaches might have been due to ill-fitting glasses as the study participants often wore 'one size fits all' blue blocking glasses. Finding a pair of blue-blocking glasses that fit well is highly recommended.
Another key issue is to ensure that any blue blocking glasses you might buy are properly tested and come with some sort of quality assurance.
There are no long-term studies on the safety of blue-blocking glasses. As we have seen the blue light has myriad of roles in the body and it would be very important to ensure that blue blocking glasses are not harming our health by switching off some other key function that blue light plays.
It seems clear that blue light is crucial not just for image formation but for the optimal regulation of circadian, neuroendocrine and neurobehavioral functions and systems. A 2017 review paper states that blue light related 'misalignment of circadian rhythmicity is observed in numerous conditions, including aging, and is thought to be involved in the development of age-related disorders, such as depression, diabetes, hypertension, obesity, and cancer' (24).
Perhaps that is true. Either way, as predicted, this is way longer than a 140 character tweet.
That being said, there is no proof that blue blocking glasses can help reverse any of this shopping list of health-related conditions. Additionally, is really advisable to block blue light? The response of the body to blue light is extremely complex.
Blue-blocking glasses seems like a very blunt instrument indeed. Using blue blocking glasses to try to achieve one specific health benefit is over-simplistic as it will also shut off other downstream effects of blue light (some of which may be beneficial).
We have no long-term studies of blue-blocking glasses to reassure us that blue blockers are safe. Perhaps some less drastic attempts at reducing our blue light exposure like reading actual physical books and cutting down our screen time might be a better way to go?