Four years ago this summer, as part of deciding to have cataract surgery, I read a lot about eye health and function. Coincidentally, I also read a story in the Sports section of The New York Times: ‘Hitters With Blue Eyes Are Wary About Glare’. Who knew that people with blue eyes, of whom I am one, are more susceptible to glare and brightness than those with dark eyes? Not me, although I then immediately understood why I always needed to wear sunglasses, even on days or at a time of day when almost no one else was doing so.
Clearly the medical staff of the New York Mets understood, as they advised their few blue-eyed players, like (back then) Jason Bay, about how to deal with the greater difficulty they experienced in seeing the ball in day games, as opposed to ones at night. In fact, it was all about sunglasses:
… Bay reached into his locker and pulled out a 24-inch black case containing an array of sleek sunglasses. There were light ones for cloudy days, medium ones for lightly overcast days, and dark ones for, as he put it, staring straight into the sun.
“I take my sunglasses very seriously,” he said.
Now, I take them very seriously too, but there is much more to it than simply light vs. dark, and that is ultimately the larger story behind this post.
For at least three decades, I had worn sunglasses with copper-colored lenses (or amber, bronze, or brown, depending on brand and market-speak). I liked not only how the world appeared through them, but also what seemed like enhanced depth perception. In my immediate post-Jason Bay period, I learned that I had been eschewing color-neutral lenses (gray, green) and opting instead for enhanced- or high-contrast lenses. If you have ever watched biathletes at the Winter Olympics, skiing through the woods, then stopping to unsling a rifle and fire away at a distant target, they were probably wearing rose or yellow lenses, the acme of high-contrast.
Suffice to say, I now have a pair with blue-mirrored, gray lenses — the blue “mirror” is not a coating, but a metal-impregnated layer, one of about a dozen in the overall lens composite — for bright, full sun. These are my every-day, most-of-the-year pair. I have some other pairs — I respectfully decline to say exactly which or how many — for enhanced contrast in a variety of conditions that I can reasonably expect to encounter during a year in the Northeast. None of them, however, is over-the-top, fine-tuned for, say, a baseball stadium in Florida on a humid day during Spring training between 2:00 and 5:00 pm.
My other (non-gray) pairs fall in the broad category of “blue blockers.” The term derives from the fact that lenses of those colors preferentially absorb blue wavelengths out of the natural spectrum of sunlight. As it happens, blue light is the most difficult for the eye to handle, so if that component is reduced before light gets to our eyes, then our vision tends to be better — higher contrast, enhanced depth perception, better tracking of a baseball. Or of a deer darting out of the woods across the road at dusk.
There is just one difficulty with this situation, tied to the interplay between blue light and our biochemistry: the blue wavelengths (roughly 450-480 nanometers) in natural daylight signal to the pineal gland not to produce melatonin, an important hormone in regulating circadian rhythms. Or, said the other way around, the evening onset of darkness — and natural absence of blue light — signals that it’s time to produce melatonin and get ready to sleep.
Notice that, all other things being equal, this pattern is a good thing: we evolved to accommodate the presence of blue light during the day and its absence at night. Unfortunately, modern technology can mess with either or both of these situations, and that is not good. We’ll look first at a familiar problem, too much blue light in the evening and its impact on melatonin and sleep.
The blue light-melatonin relationship in humans has been firmly established in the scientific literature over the past 15 years or so. It became prominent in the press, however, following the introduction of blue light-emitting handheld electronic devices, including the iPhone (2007) and especially the iPad (2010). Here is a sample of attention-getting, not to say alarmist, journalistic titles:
* ‘Blue light has a dark side’, Harvard Health Publications (2012)
* ‘How artificial light is wrecking your sleep, and what to do about it’, Let’s Take Back Your Health (2013)
* ‘Blue light from electronics disturbs sleep, especially for teenagers’, The Washington Post (2014)
* ‘Can Orange Glasses Help You Sleep Better?’, Wired Well, NYT Now (2015)
All of this is backed up, both specifically and generically, in peer-reviewed scientific articles, including the two 2001 papers that first documented the blue-wavelength sensitivity:
* Action Spectrum for Melatonin Regulation in Humans: Evidence for a Novel Circadian Photoreceptor, Journal of Neuroscience (2001)
* An action spectrum for melatonin suppression: evidence for a novel non-rod, non-cone photoreceptor system in humans, Journal of Physiology (2001)
* Amber lenses to block blue light and improve sleep: a randomized trial, Chronobiology International (2009)
* Light level and duration of exposure determine the impact of self-luminous tablets on melatonin suppression, Applied Ergonomics (2013) [cited again below]
* Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness, Proceedings of the National Academy of Sciences (2014/2015)
You don’t even have to read these news articles or scientific papers (although I have read them all and more), because the titles alone tell a definitive and overwhelming story. Here is the recipe for messing up your sleep: For the last few hours before bedtime, watch a movie on your iPad or read a book on your backlit Kindle; have the television glowing in the background, too; and stop on the way to bed to make one last check of email on your computer. Welcome to the upper-right corner of the expanded sketch (below), and good luck dealing with things the next morning.
The fourth journalistic title and the third scientific one discuss a counter-strategy that I have used in an attempt to escape from that corner: wearing a pair of non-polarizing, blue-blocker “orange” glasses for those final few hours of the evening. I can’t say that it worked particularly well for me, but then I haven’t been very faithful or consistent about it. Seasonally, a lot of my blue-based evening activity is watching sports, and I find it a bit tough to distinguish what’s going on if both teams’ uniforms are a muddy mix of orange and gray. Ditto for the appeal of reading orange-tinged pages, whether paper or electronic.
There is something else, however, that surprises and concerns me more than the melatonin-suppressing effects of the blue light emitted by our handheld electronics (to say nothing of the longer-standing, nighttime illumination of our homes, our cities, our entire way of life). It is demarcated by the empty spot in the lower-left corner of that sketch (above), and it is this:
Nowhere in the research literature or press have I been able to find mention of the inverse problem, namely, routinely wearing blue-blocker sunglasses during daytime should enhance melatonin production precisely when you don’t want it (lower-left field below).
Notice that this is completely separate from, and additive to, any effect that your evening habits may have on suppressing melatonin production (upper-right field above). If you wear sunglasses with non-color-neutral lenses for several hours during the day, then over the long haul your circadian biochemistry will surely be at least as confused by that as it is from your staring at an iPad for a few hours each night. For many of us, the two effects will concatenate and reinforce each other, with the result that you could find yourself oscillating along the upper-right-to-lower-left “technology axis,” instead of the upper-left-to-lower-right “evolutionary axis.” Somewhere in one of those aberrant oscillations you might even find yourself unable to sleep at 3:00 am and sitting in front of a screen, writing a blog post about blue blockers, iPads, and melatonin.
How do we explain the apparent silence in both the research community and the press about the potential hazards for the general, sunglasses-wearing public in the lower-left quadrant? The press is easy to understand. In general, they take their cues and clues from the researchers, so they are merely followers. But the researchers themselves?…
A cynical reader will think, oh, they know all about it, but they don’t want to say anything because it would upset the manufacturers of sunglasses, from whom they probably get all of their research funding. (There is surely an entropic law that says “Conspiracy theories based on any reasoned scientific issue will tend toward a maximum.”) I grant that this is a formal possibility, but based on my several decades of experience in academia, I can assure you that for the overwhelming majority of us it is all about getting the right answer. Preferably being first to get it, but getting it nonetheless, whatever the consequences for industries, governments, religions, or sunglasses manufacturers.
Alternatively, a reader with an analytical perspective might say, hold on, maybe they concluded that the effect you are talking about would be too small to measure; or maybe they tried but the results weren’t reliable enough to be published; or maybe they described it, but you just didn’t grasp what they were saying. Yes, all good points. I thought the same thing obviously, so in fairness, both to myself and the researchers involved, here are two “qualifiers.”
Firstly, I am a lab scientist — a geologist/geochemist, which means a physical scientist, but not a life scientist. I can pretty easily follow the journal articles with regard to research protocols, lab and statistical methodologies, and the general discussions. I am not remotely a subject-matter expert, however, in the fields — endocrinology, neuroscience, ophthalmology, sleep medicine — of these researchers, so there are lots of things I have likely missed, both nuanced and blatant.
Secondly, I used a couple of weasel-words in the foregoing: the word “routinely” in that bolded phrase “routinely wearing blue-blocker sunglasses during daytime”; and “apparent” in “the apparent silence about the hazards” of blue-blockers. The reason for this is that at least three research groups, in fact, have data demonstrating that change in melatonin production when wearing blue-blockers is easily measured and statistically different from baseline:
- L. Kayumov et al. (Toronto), Blocking Low-Wavelength Light Prevents Nocturnal Melatonin Suppression with No Adverse Effect on Performance during Simulated Shift Work, The Journal of Clinical Endocrinology & Metabolism (2005)
- A. Sasseville et al. (Laval), Blue blocker glasses impede the capacity of bright light to suppress melatonin production, Journal of Pineal Research (2006)
- B. Wood et al. (RPI) Light level and duration of exposure determine the impact of self-luminous tablets on melatonin suppression, Applied Ergonomics (2013)
To me, again as a scientifically-literate outsider, that means there is no reason to be concerned about either detection sensitivities or measurement reproducibility. There may (or may not) be cause for concern, however, over something else: As the titles hint, all three studies actually focused on melatonin suppression due to bright light sources, because they were conducted during evening and nighttime hours, in the upper-right corner of the grid. This was done, in turn, because all three lab groups were interested to varying degrees in the implication of their research for night-shift workers. Thus, while analytical issues are almost certainly not a concern in testing the effect of blue-blockers on melatonin enhancement during extended daytime use in the lower-left corner, it is an open question as to what the optimum experimental protocols might be for such studies.
So now we return to the question in the title of this post, “Would you like melatonin with those?…” Imagine that the context is an optician or store clerk asking, “Do you want your new sunglasses to block blue light and allow melatonin production during the day, even though there is a risk that it can affect your sleep at night?” No one is likely to ask that, however, in the absence of any publicly-reported, scientifically-credible research documenting the magnitude of blue-blockers on daytime melatonin levels.
My instinct, which is all I have to go on, says that this absence is probably a result of the fine-grained compartmentalization of much modern science. After my aforementioned cataract surgery and during a follow-up appointment with my opthamologist, the benefit of wearing sunglasses came up.
me: Does it matter what type of lenses I use, gray, copper or other contrast-enhancing?
he: Use whatever you like.
me: You do realize that wearing blue blockers during daylight will enhance melatonin production, precisely when you don’t want it, with an attendant potential for long-term sleep disruption?
he: [silent, but with a look of complete surprise and turning wheels, which seemed to say, OMG, I never thought of that!]
Mind you, he is a practitioner (and an excellent one), not a researcher. But the “silo effect,” in this case separating his applied ophthalmology from basic endocrinology and sleep research, was surely there.
Here is a simple and simple-minded parallel that captures the essence of the larger situation, as nearly as I can tell. Imagine that you are in the teachers’ lounge at a school, listening to the math faculty discuss the teaching of fractions. Someone says, “I’m going to show my students how to change the value of the fraction, V = (numerator)/(denominator), by increasing and decreasing the value of the numerator, and I’ll give them problems so that they can work through some examples.” Much discussion follows among the group about changing the numerator, and you (the observer) keep waiting for someone to discuss the inverse situation, changing the value of the denominator. But it doesn’t happen. At first you think, well, it’s so obvious they just aren’t bothering to bring it up. But the longer it goes on, the more you begin to realize, wait, maybe they haven’t actually noticed that they can change the denominator….
Is that really possible here? Has no one in these research groups realized that there is a “denominator” in the “melatonin fraction”? Or could there be a different “compartmentalization” at work? A society-level factor could be that purchase of sunglasses for daytime use is done for enhancement all right, but enhancement of fashion status and sports performance, not of melatonin. It’s a pretty safe guess that both of those groups of purchasers will buy what they want anyway. On the other hand, any lab-level factor I suggest is pure speculation because decisions on research topics are typically the purview of only a few group leaders. That leads me full-circle to one last question, asked not entirely facetiously: What is the personal “sensitivity” of those group leaders, that is, do any of them have blue eyes?…