I love them. My brother got me an iPad for Christmas a couple years ago and I’ve really enjoyed filling my ebookshelves ever since.
It’s that immediate gratification. See a book you want, and you can purchase it and start reading it right now.
What’s not to like?
But then I did some extensive research on an article I recently wrote for a client, and realized that my habit of including my iPad in my stack of paperback and hardcovers that I read before bed was not a good idea.
It’s bad for you—and it has nothing to do with being old school or new school or anything in between.
It has nothing to do with literature at all, and everything to do with your health.
Ebooks Expose You to Something Potentially Dangerous
You’ve probably heard that shift work isn’t good for you. You may have thought it had something to do with lack of sleep, interrupting sleep patterns, or just throwing off the body’s schedule in general. If so, you were right—but you may have missed one key factor.
There were a few studies beginning at the turn of the century that raised some concerns. In 2001, researchers followed just over 800 participants who were diagnosed with breast cancer between 1992 and 1995, and compared them with about the same number of controls who were not. Those who worked the graveyard shift were more at risk for breast cancer, but not necessarily for the reasons you may expect.
It had something to do with sleep, but not necessarily whether participants were getting enough (though that was related). Instead, it was all about the amount of light they were exposed to prior to and during sleep, and how that affected levels of a certain hormone called “melatonin.”
Risk was highest among those who didn’t sleep at night when levels of melatonin—the hormone that regulates sleep—is naturally at its highest. Those with the brightest bedrooms were also more vulnerable to the disease.
Researchers concluded exposure to light at night suppresses the production of melatonin, which can cause many problems—including the release of extra estrogen into the system (estrogen has been linked with risk of breast cancer).
What Does it Have to Do With Light?
Scientists were onto something. In 2005, Cancer Research published the results of an animal study showing that artificial light stimulated the growth of human breast tumors by suppressing levels of melatonin. Increased periods of nighttime darkness, on the other hand, slowed the growth of these tumors.
You may have heard that melatonin helps you sleep. Turns out that artificial light not only reduces melatonin levels, but the reduction does more than mess with sleep—it can also disrupt other processes in the body, allowing cancer cells to take hold.
“Evidence is emerging that disruption of one’s circadian clock is associated with cancer in humans,” said lead researcher David Blask, M.D., Ph.D, “and that interference with internal timekeeping can tip the balance in favor of tumor development.”
What is Melatonin?
Melatonin is important for a number of things, but its main job is to regulate the body clock, or circadian rhythm. This is the clock that tells us when to wake up and when we’re tired and need to go to bed. When the sun comes up, production of melatonin naturally drops. When the sun goes down, the body produces more.
Everything’s fine as long as we go along with the natural day/night cycles we’ve evolved with. Artificial light, however, allows us to go against those natural cycles. We can get up at 2:00 in the morning and work, for example, and go to bed at ten o’clock the next morning if we want to. We may even get used to that schedule, but according to studies, it’s not good for us.
That’s because the exposure to lights—even artificial lights—tells the body to produce less melatonin, throwing our natural cycles out of whack.
Disrupt your natural cycle and beware the consequences.
Over time, reduced production of melatonin can harm other parts of your system. Scientists believe the hormone is involved in a woman’s menstrual cycle, that it has antioxidant effects—helping us to avoid diseases like heart disease and diabetes—and that it strengthens the immune system.
Take all that away, and you become more vulnerable to health problems.
Too Much Light Linked with Other Diseases
As researchers continued to study exposure to light at night and risk of disease, they found even more evidence to suggest all these lights aren’t good for us.
- Obesity: In 2010, researchers found that the disruption of circadian rhythms, a lack of adequate sleep, and the suppression of melatonin aggravated weight gain, and were potential contributors to our current obesity epidemic.
- Diabetes: In 2011, researchers found that exposure to electrical light between dusk and bedtime strongly affected melatonin levels, which in turn, could affect the body’s ability to regulate temperature, blood pressure, and glucose levels. Participants who left lights on during sleep had melatonin levels suppressed by greater than 50 percent.
- Depression: In 2013, researchers reported that animals exposed to artificial light at night displayed symptoms of depression, and that these symptoms were reversed when the light was removed.
- Cancer: In addition to the shift work studies above, other research found women with breast cancer had lower levels of melatonin than women without breast cancer, and that melatonin supplements may help support the effects of chemotherapy on breast cancer. Studies have also found that men with prostate cancer also have lower levels of melatonin than men without the disease.
- More: In March 2015, researchers published another study suggesting our modern habits of having the lights on at all hours of the day and night could be putting us at risk of obesity, diabetes, cancer, and other health issues. They noted we’re not getting enough natural light during the day, and too much artificial light at night.
We’re Suffering from “Light Pollution”
Our exposure to artificial light has become so concerning scientists are now calling it a genuine health risk.
In 2012, the American Medical Association officially recognized light exposure as concerning for public health, and voted to look into changes in lighting technologies, and to encourage additional studies on the link between light at night and many of our most serious modern-day health challenges.
A few years earlier, in 2009, the journal Environmental Heath Perspectives published an article on the “effects of light pollution,” noting that “two-thirds of the U.S. population and more than one-half of the European population have already lost the ability to see the Milky Way with the naked eye.”
They went on to review the light-health connection, and referred to two Israel studies linking light pollution with cancer:
“Stevens was part of a study team that used satellite photos to gauge the level of nighttime artificial light in 147 communities in Israel, then overlaid the photos with a map detailing the distribution of breast cancer cases. The results showed a statistically significant correlation between outdoor artificial light at night and breast cancer, even when controlling for population density, affluence, and air pollution. Women living in neighborhoods where it was bright enough to read a book outside at midnight had a 73% higher risk of developing breast cancer than those residing in areas with the least outdoor artificial lighting.”
What does all this have to do with ebooks?
Well, all of our gadgets tend to emit light—blue light, in particular.
Blue Light Particularly Dangerous
Computers, smart phones, and yes, tablets, emit blue light—which of all the colors in the spectrum, suppresses melatonin the most.
In 2009, researchers found that participants who wore blue-blocking glasses for three hours before bed slept better than those who wore yellow-tinted glasses that blocked ultraviolet light only.
Three years earlier, scientists also discovered the circadian clock is most sensitive to blue light (which comes in short wavelengths). In 2013, researchers reported that self-luminating displays (like those in tablets and cell phones) “emit optical radiation at short wavelengths, close to the peak sensitivity of melatonin suppression.”
As for ebooks? In 2015, researchers compared the effects of reading a regular book with those of reading an electronic book in the hours before bedtime.
Participants using the e-reader (iPad):
- took longer to fall asleep,
- had reduced evening sleepiness,
- secreted less melatonin,
- experienced circadian rhythm disruptions,
- and were more likely to be sleepy the next morning than those who read a regular, printed book.
Lead researcher Prof Charles Czeisler, told the BBC News website:
“The light emitted by most e-readers is shining directly into the eyes of the reader, whereas from a printed book or the original Kindle, the reader is only exposed to reflected light from the pages of the book.”
Read a Regular Book Instead
My solution to all this?
Save the ebooks for daytime reading, and choose a print book at night before bed.
A regular book read under an old-fashioned soft light (new LED lights also emit more blue light) is just the type of quiet nighttime activity that doctors recommend to improve sleep.
If you’re traveling and all you have is your tablet, try the following tips to reduce the damage, but realize that you may be affecting your sleep and your melatonin levels. Might be better to take along that light paperback!
- Try a blue light filter: Since blue light has the greatest affect on melatonin, try a blue-light filter. There are several out there that you can download and install into your tablet. Google has one here.
- Try f.lux: This application adjusts the brightness on your display depending on the time of day and the volume of ambient light in your room, making adjustments at night to help reduce eye-strain. F.lux is available for your computer and your iPhone/iPad. For Android devices, try “twilight.”
- Adjust the brightness: Use your brightness slide to dim the light when you’re reading at night. If you’re reading on a smart phone, you may need to download an app to be able to adjust the brightness of your screen.
- Use a standard Kindle: The standard Kindle’s display is closer to reading print than other displays. Researchers noted in the 2015 study mentioned above that the standard Kindle (and any other e-ink e-readers that don’t use light) would prove an exception to their findings. Front-lit e-readers like the Kindle Paperwhite and the Nook GlowLight do use small LED lights around the screen to cast a glow. These may be less damaging to melatonin production than bright iPads, for instance, but we have no studies on these yet to be sure. (And as mentioned, LEDs emit more blue light than incandescent bulbs.) You can dim the brightness on these, and other tablets like the Kindle Fire.
- Keep other lights low: The good thing about reading a print book under a soft light in an otherwise dark room is that it signals your body to ramp up production because the overall light in the room is low. You may be able to accomplish nearly the same effect by turning off all other lights in the room, and either reading your standard Kindle with a soft light or reading your other e-reader with f.lux installed or at the very least, at a reduced brightness level.
- Use blue-blocking glasses: Hey, now you have a reason to wear your sunglasses at night. Amber-lens or “blue-blocking” sunglasses can protect you from the blue light your device emits, reducing the effect on melatonin. If you’re somewhere you can’t control your exposure to lights, they can also help your body wind down at night. There are many brands out there—Uvex and Solar Shield are examples.
- Use a candle: I wouldn’t recommend a real one, as that could be a fire danger if you fall asleep while reading. You can, however, use battery-operated “flameless” candles to read by. They emit little blue light and cast a soft glow that will help your body ramp up melatonin and get ready to sleep. I would advise against those that emit scent, as usually they work with chemicals that aren’t good for you.
Do you read using bright tablets at night? Please share your thoughts.
Scott Davis, et al., “Night Shift Word, Light at Night, and Risk of Breast Cancer,” J Natl Cancer Inst 2001; 93(20):1557-1562, http://jnci.oxfordjournals.org/content/93/20/1557.abstract?ijkey=5c7533c6ad6efcbfdd1a9d2d5a0a3c311f5b05b6&keytype2=tf_ipsecsha.
Eva S. Shcernhammer, et al., “Rotating Night Shifts and Risk of Breast Cancer in Women Participanting in the Nurses’ Health Study,” J Natl Cancer Inst, 2001; 93(20):1563-1568, http://jnci.oxfordjournals.org/content/93/20/1563.abstract?ijkey=8522777aa4cf58b0915363dd55297c3ea481530d&keytype2=tf_ipsecsha.
National Institute of Environmental Health Sciences, “New Research Shows Artificial Light at Night Stimulates Breast Cancer Growth in Laboratory Mice,” National Institutes of Health, December 19, 2005, http://www.nih.gov/news/pr/dec2005/niehs-19.htm.
“Melatonin,” University of Maryland Medical Center, https://umm.edu/health/medical/altmed/supplement/melatonin.
Russel J. Reiter, et al,. “Obesity and metabolic syndrome: Association with chronodistruption, sleep deprivation, and melatonin suppression,” Annals of Medicine, September 2012; 44(6):564-577, http://informahealthcare.com/doi/abs/10.3109/07853890.2011.586365.
Richard G. Stevens, Yong Zhu, “Electric light, particularly at night, disrupts human circadian rhythmicity: is that a problem?” Philisophical Transactions B, March 16, 2015, DOI: 10.1098/rstb.2014.0120, http://rstb.royalsocietypublishing.org/content/370/1667/20140120.
Gooley JJ, et al., “Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans,” J Clin Endocrinol Metab, March 2011; 96(3):E463-72, http://www.ncbi.nlm.nih.gov/pubmed/21193540.
Chris DeFrancesco, “AMA: Health Implications of Light at Night ‘Serious,” UConn Health Today, June 20, 2012, http://today.uconn.edu/blog/2012/06/ama-health-implications-of-light-at-night-serious/.
Ron Chepesiuk, “Missing the Dark: Health Effects of Light Pollution,” Environmental Health Perspectives,” January 2009; 117(1):A20-A27, http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2627884/.
Anne-Marie Chang, et al., “Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness,” PNAS, January 27, 2015; 112(4):1232-1237, http://www.pnas.org/content/112/4/1232.full.pdf.
Sasseville A, et al., “Blue blocker glasses impeded the capacity of bright light to suppress melatonin production,” J Pineal Res., August 2006; 41(1):73-8, http://www.ncbi.nlm.nih.gov/pubmed/16842544.
Burkhart K, Phelps JR, “Amber lenses to block blue light and improve sleep: a randomized trial,” Chronobiol Int., December 2009; 26(8):1602-12, http://www.ncbi.nlm.nih.gov/pubmed/20030543.
Wood B, et al., “Light level and duration of exposure determine the impact of self-luminous tablets on melatonin suppression,” Appl Ergon., March 2013; 44(2):237-40, http://www.ncbi.nlm.nih.gov/pubmed/22850476.
Rebekah Mullaney, “Light from Self-Luminous Tablet Computers can Affect Evening Melatonin, Delaying Sleep,” Renssalaer Polytechnic Institute, August 27, 2012, http://news.rpi.edu/luwakkey/3074.
James Gallagher, “E-books ‘damage sleep and health,’ doctors warn,” BBC, December 23, 2014, http://www.bbc.com/news/health-30574260.