Welcome to the next entry in this blog series all about sleep, how you can sleep better, and tools to accomplish those goals. Today, we will be looking at light and how it affects your sleep. We’ll be reviewing a variety of different applications for light to help you sleep as well as the hindrance light can be to your sleep. Let’s dive in!
I think it’s no surprise to people that light can keep you awake. If you have ever woken up in the middle of the night to use the restroom and you turn on the bathroom light, you’re immediately flooded with an influx of ostensibly painful light. You squint your eyes as much as you can to block all that light, so it doesn’t wake you up or maybe you’re talented and don’t need light to use the bathroom. In either case, light plays a role in waking you up. You will likely be able to fall back asleep even if you did view that light, but it can take you a bit longer to fall asleep. Why is that?
We’ll begin by going back a couple of blog posts. Do you remember melatonin? That hormone your body naturally makes and the supplement you can take to help you sleep? That hormone is heavily influenced by light! No matter what kind of light it is, melatonin production stops when our eyes see light. If you recall, melatonin is responsible not for generating sleep but for the timing of sleep so when you view light and your melatonin production is halted, it makes sense why it takes you a little longer to go back to sleep. Sometimes, you may even experience a full-blown awakening after viewing light in a situation like this. Nightlights are your friend and an inexpensive tool to use to prevent something like this from happening. The dim light should not interfere with your melatonin production and can be bright enough to let you do what you need to do.
Another activity that requires light that can hinder your sleep is technology. Many people will check their email one last time before bed or scroll TikTok or watch a TV show before bed and then wonder why it may take them a little longer to get to sleep. Blue light has a reputation for being harmful to the eyes and sleep and there is a good reason for this, but it seems, at least from the perspective of sleep, that might be changing. There was a study conducted out of Harvard where the researchers would give participants an iPad to read a book, in dim light, before bed. The study showed a delayed release of melatonin and, a reduction in REM sleep, and the sleep quality of the participants was poor even a couple of days after the iPad reading. Naturally, you’d think the recommendation would follow that blue light before bed is bad. However, there have been studies by Flindel University in Australia that indicate that it is less about blue light but the cognitively stimulating properties of the iPad itself, the book that’s being read, or the activity being engaged with. In a podcast with Dr. Peter Attia, Dr. Matthew Walker stated that it seems to be more of a masking effect for our sleepiness than anything else when it comes to the iPad and how physiologically arousing it is. He also stated that light can still have an effect and to avoid it if you can, but perhaps it’s the design of the iPad to be stimulating that causes this masking and not as much the blue light coming from the iPad. “So does this mean I can still read my favorite book on my iPad before bed?” Given the available data on light and how it interacts with our melatonin production and how the rest of your body reacts to the presence of light, it is still probably best to abstain from it 30 minutes to an hour before going to bed. However, as always, life is to be lived and if you want to read a book on your iPad, read that book!
So, how does light help you sleep? This question has somewhat of a complicated answer but essentially, it has to do with your Suprachiasmatic Nucleus. I mentioned this in an earlier post and now that we’re on the topic of light, you can learn a fancy sciency word to impress your friends! The SCN, Suprachiasmatic Nucleus, is responsible for many things. It’s located right above the roof of your mouth, and it dictates your circadian rhythm. It dictates many other things because of that including metabolism, alertness, sleep-wake timing, and food intake. There is a fantastic podcast that you can search for on YouTube or Spotify by Dr. Andrew Huberman where he interviews Dr. Samer Hattar who discusses the influence of light on your SCN and therefore the rest of your body. If you’re ever curious, give it a listen, but for now, we’ll stick to light and sleep. For those who live in parts of the world where there are long periods of darkness, like parts of Alaska, lightbox therapy is used. Essentially, the lightbox replaces the sun for your SCN so when you wake up, you turn the lightbox on while you’re doing your morning routine and while you’re going through your day. When your SCN sees light, it triggers a whole host of events. The sun, even on a cloudy day, has significantly more lux, the measurement of light, than a lightbox but if you’re getting no sun, then some lux is needed to maintain that circadian rhythm. The relationship between light and the SCN is why having a consistent bedtime is helpful, and why 45 minutes of sunlight in the morning, is beneficial for regulating your circadian rhythm. Since the lightbox replaces the sun, it helps you maintain that rhythm and when your circadian rhythm is consistent, your quality of sleep increases. This is also something shift workers can do as well to help with their sleep, that, and melatonin. I would recommend seeking out a sleep doctor to assess the proper lightbox routine if that’s necessary because there are protocols, and they may be different from person to person.
I hope you have enjoyed learning a little bit about light, sleep, circadian rhythm, and the Suprachiasmatic Nucleus! With that, I will say good night and I hope you sleep well!
Fun fact for your next party: On a cloudy day, the sun will average 1000 lux while on a cloudless day, it can range from 10,000 to 25,000 without direct sunlight. In comparison, a well-lit office space is between 300-500 and an average lightbox is around 600-700, though they can be brighter.