Will exposure to blue light before bed delay sleep quality overall?
The recent adage that don’t watch screens before bedtime or else you cannot sleep may have some truth to it. This is a recent phenomenon going back the last 2 decades when the laptops and later mobiles phone sales exploded across the world and various apps and games began to vie for our attention. Attention to our digital toys was relegated to the night after completing the day’s work just before bedtime. In India 87% of us use our mobile phones before bedtime (The Great Indian Sleep Scorecard by Wakefit), which might have contributed to our second ranking in the 18-country sleep deprivation survey by Fitbit.
Artificial light is pervasive in today’s world, lighting up our homes in the form of bulbs, tubelights, chandeliers; and we spend less time outdoors, reducing our exposure to natural light. Over the course of evolution, light has been a driving force in the various physiological changes that have led us to where we are now. Artificial and natural light have a marked difference in their luminosities.
Science has shown that exposure to light at dusk postpones our sleepiness, while exposure to sunlight in the morning prepones our sleepiness. This forms the scientific basis to argue for the late-night exposure to screens affecting sleep. However, light itself is not bad but the bluish end of the spectrum with its short wavelength, which has been shown to be more damaging to our sleep. It is not the sleep onset delay, which was shown to be 10 mins delayed with reading a ebook as opposed to reading a physical book, that is the problem, but rather the other effects like slowing down sleep promoting (among other functions) hormone melatonin production, decrease in deep sleep which is memory consolidating at the expense of light sleep, circadian rhythm disturbances, (a 24 hour body clock that coordinates among other things, sleep), more nighttime awakenings and reduction in morning alertness ((Green et al, 2017).
Source: Sleepfoundation.org
Another recent study however found that cognitive performance was not reduced drastically with low wavelength light (blue) since our amygdala (responsible for memory, learning and suppressing melatonin production) was stimulated by light with shorter wavelengths (Kazemi et al, 2019). This means that while you will generally stay alert while looking at the screen, it’s not good for the human body not least because melatonin, which is a strong antioxidant, has reduced release with blue light. However, Prof. Russell Foster, Professor of circadian neuroscience at the University of Oxford argues in his book, LifeTime, that the mobiles are not bad because they emit blue light but because they produce this alerting activity in the brain. Other factors including watching mobiles in a bright room (which has greater impact on the circadian system) and watching mobiles in lying position with a shorter viewing distance also play a crucial role in degrading your sleep quality (Krishnan et al, 2020).
How do circadian rhythms work?, Sci. Focus. (n.d.). https://www.sciencefocus.c om/the-human-body/how-do-circadian-rhythms-work/.
While turning on night mode on your mobile or using a night filter on your laptop can reduce the short wavelength exposure, it still does not solve the problem of carrying your device to bed. If you feel restless after sending the last email or need to get to the next level in your favorite game, then you need to really think hard. The only exception is when you are in a new relationship! On a serious note though, maybe you can set an out of office message saying you check your emails last at 8PM or you only check messages 4 times a day or whatever works for you. Apple revealed that we unlock our phones 80 times a day for usage anywhere from 1 to 10 hours (for some the phone may be how they work and that’s an exception). The average is 3 hours 58 minutes of which a considerable amount if before sleep.
New habits are difficult to form and that’s why we have a mortal fear of change. But new habit forming apps can help to build new sleep habits. There are a multitude of habit apps (Streaks, HabitNow, Habitify etc). There are a few other things you can try
- Turn off all alerts – this really helps and once it becomes a habit, the FOMO goes down
- Decide how you can be reached and till when
- Sometimes a smartwatch can help if you are disciplined enough to only allow invites and phone calls (and some of them you can reject from your wrist)
- Turn the airplane mode on about 30 mins before bed or even earlier
- Install a habit app as described above
No doubt it’s hard work, but when your health is on the line, wouldn’t you do this?
References:
Nearly half of India wakes up feeling tired according to research (TimesofIndia, 2024)
Motamedzadeh, M., Golmohammadi, R., Kazemi, R., Heidarimoghadam, R. (2017). The effect of blue-enriched white light on cognitive performances and sleepiness of night-shift workers: A field study. Physiol. Behav. 177, 208–214. doi: 10.1016/j.physbeh.2017.05.008
Krishnan B, Sanjeev RK, Latti RG. Quality of Sleep Among Bedtime Smartphone Users. Int J Prev Med. 2020 Aug 6;11:114. doi: 10.4103/ijpvm.IJPVM_266_19. PMID: 33088442; PMCID: PMC7554597.
Green, A., Cohen-Zion, M., Haim, A., & Dagan, Y. (2017). Evening light exposure to computer screens disrupts human sleep, biological rhythms, and attention abilities. Chronobiology International, 34(7), 855–865. https://doi.org/10.1080/07420528.2017.1324878