The fourth variable that I will be manipulating across a two week period to examine its impact on sleep is blue-light blocking glasses.
I will discuss what my data shows, how easy or difficult I found this strategy to implement, and what previous research says. These three factors will be combined for an overall score and grade on how effective wearing blue-light blocking glasses in the last two hours before bedtime is at helping people to improve their sleep.
I bought a pair of UVEX Blue-light blocking glasses for $22AUD with free delivery from the website www.optimoz.com.au. As you can see, the first picture above is of glasses for people who don’t need reading glasses, and the second picture is of glasses that can be worn over the top of reading glasses. Here is their description on the product:
UVEX have produced a set of eyewear designed for use by dental or medical practitioners while working under strong UV lamps. These are orange lensed glasses, but there is more to them than just the orange colour. These glasses use UVEX’s patented “Spectrum Control Technology” to filter out specific colours of the light spectrum.
The light that is going to hurt your sleep performance is any blue light with a wavelength below 520nm (however 440-480 is a particularly critical range). This eyewear will selectively block out any light less than 550nm while allowing 80%-90% of all other light through. Wear these for a couple hours before bed and you will eliminate the impacts of blue light on your sleep!
Why Blue Light?
For a long time, scientists thought that the only receptors in our eyes were rods and cones. However, in 2001, a third lot of receptors were discovered, whose only role was to determine whether it was light or dark outside (Brainard, 2001).
Interestingly, these light/dark receptors only respond to blue wavelengths of light, as shown by the effective bandwidth in the graph below:
Blue light is present in white or natural light, as shown in red and yellow in the graph above. Given the intensity of these wavelengths outside during the day, our light/dark receptors will tell our brain that it is light, and help us to feel energetic and alert. For this reason it is actually considered helpful to get 30-minutes of exposure to sunlight in the morning.
Blue light boxes or glasses with blue lights on them can even be bought online and used by people with Delayed Sleep Phase Disorder (DSPD) to help them wake up and get going at an earlier time than they usually would (as well as get to sleep earlier that next night).
Unfortunately, blue light is also highly prevalent in LED screens including televisions, computers, tablets and smart phones. Whilst this isn’t a problem during the day, it can quickly become one at night.
The most important hormone for sleep is melatonin, which responds to signals of darkness from our light/dark receptors, and usually begins to be released about 2 hours before our usual bedtime. If we are exposed to high levels of blue-light wavelengths during this time, our light/dark receptors will tell our internal body clock that it is still daytime, and our melatonin production will be suppressed. This can then contribute to more difficulties in falling asleep and staying asleep, as well as poorer sleep quality and a shorter sleep duration (Cajochen, Krauchi & Wirz-Justice, 2003).
My reason for trialling blue-light blocking glasses builds upon what I discovered in episode 3 on Sleep and TV. Across this two week period, I found that not watching TV in the last two hours before bed was more helpful than watching TV for my sleep.
What I don’t know is if it was purely the bright light or blue light from the TV that led to my sleep being worse (by suppressing melatonin), or if the meditation and reading that I did before sleep on the no TV week was more relaxing than watching TV? In order to answer this question, I needed to ask another:
What if I could watch TV or use the computer before bed without it negatively impacting my sleep?
Blue-light blocking glasses are the best way to find out.
For a two-week period, I decided to use bright-screen technology for the last two hours each night before bed. On each week I used the computer on 4 nights, and either my phone or the TV on 3 nights.
For the first week, I did not use any programs or glasses to reduce the amount of blue-light I was exposed to.
For the second week, I put on blue-light blocking glasses, and didn’t take them off until I was in bed with the lights off.
Comparison: Blue-blocking Glasses vs Bright Screens
Subjectively, My sleep efficiency, sleep quality, time taken to fall asleep, number of awakenings during the night and time awake during the night were all better with the blue blocking glasses on in comparison to being on bright screens in the last two hours before bed without them on. My wake time during the week was also much more consistent.
Surprisingly, I actually went to bed 5 minutes later per night with the blue-blocking glasses on, spent less time in bed, and slept 20 minutes less per night. This may have been due to the better sleep quality that I was getting, as I wasn’t any more tired during the day, but I was no longer getting the recommended 7 to 8 hours of sleep per night.
Objectively, the depth of my sleep was much better during the second week when I was wearing the blue-light blocking glasses. Let’s compare Feb 27 (26/2/17 on the sleep diary) to March 06 (5/3/17 on the sleep diary data). Both were Sunday nights. I had gone for a swim in the morning on both days. I didn’t have any alcohol or caffeine. I spent at least two hours on the computer before bed on both of the nights. The only difference was that I didn’t wear the glasses the first week, but did on the second.
Even though I spent two hours less in bed the second week, I was still able to attain 8 minutes more restful sleep, with a restful:light sleep ratio of 2.45:1 in comparison to 1.11:1. This meant that I felt quite refreshed and energetic the next day after wearing the blue-blocking glasses, even though I slept less than the ideal 7 to 8 hours.
IS WEARING BLUE-LIGHT BLOCKING GLASSES BEFORE BED A GOOD SLEEP STRATEGY?
Yes. I still didn’t find wearing the glasses to be quite as effective as avoiding alcohol, but better than avoiding caffeine and slightly better at improving sleep quality over not watching TV. It beat bright screens and no TV before bed on 5 to 6 out of the 9 categories that I measured on the sleep diary, so I give the effectiveness of this strategy a 20/25.
For me, it was bit annoying to have to wear the glasses whilst on my computer or the phone, but watching TV I got used to wearing the glasses pretty quickly, and felt like I could enjoy the programs just as much. The times when it might be tough are if you are going on holiday somewhere, having friends over, or staying over at someone’s house. I therefore give the applicability of this strategy a 17/25. It is pretty easy to forget to put them on, and they do look a little silly, but if used consistently they really can help.
A 2017 study found that playing games on a blue-light emitting smart-phone between 7:30pm and 10:00pm significantly decreased sleepiness and delayed melatonin onset by .24hours (as well as increased cortisol levels and body temperature) in comparison to the same subjects who played these games on a smart phone with the blue-light wavelengths removed (Heo et al., 2017).
What we don’t know enough about is if the blue-light blocking glasses are as effective as their product graph shows:
If blue-wavelengths are predominantly between 440-480nm, and the glasses block out all wavelengths below 550nm, then they will essentially have the same positive effect on our melatonin release as being in complete darkness for the last two hours before bed.
In 2016, Esaki and colleagues had eight patients with delayed sleep-phase disorder (DSPD) wear blue-light blocking glasses from 9pm onwards for a two-week period. It brought their melatonin onset forward by 78 minutes on average, and their sleep onset time was over two-hours earlier after the treatment than before it (Esaki et al., 2016).
I therefore give the science of this strategy a 38/50.
Overall, avoiding watching TV in the two hours before bed as a way to sleep better gets a score of 20/25 + 17/25 + 38/50 =
WHAT I RECOMMEND
If you can avoid bright screens in the last two hours before bed, it will help with your sleep. If you don’t want to avoid bright screens during this time, or have tried but found it too difficult to stop, do yourself a favour and get a pair of blue-light blocking glasses. For a very small investment ($22), you can watch as much TV or be on your tablet for as long as you want before bed without having to worry about the impact that it is having on your sleep.
I still don’t recommend being on your computer or phone in bed but if you are using them late at night, do download f.lux and install it on your computer, or go to settings on your iPhone and then go to display & brightness and turn on night shift starting so that it starts at least two hours before you normally go to bed.
Going forward I will be using f.lux on my computer, night shift on my phone, and blue-blocking glasses when I am watching TV at home.
Dr Damon Ashworth