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Chapter 1: What role does daylight play in regulating our sleep?
You're listening to TED Talks Daily, where we bring you new ideas to spark your curiosity every day. I'm your host, Elise Hu. If you'll allow me to brag real quick, I am very good at getting over jet lag. I'm a former international correspondent and have to do some cross-time zone travel pretty frequently.
Over the years, I've learned daylight and staying awake at daylight has really helped me in regulating sleep and correcting for jet lag. And in her talk, sleep scientist Christine Bloom gives us an explainer on why it's so effective, not just for jet lag, but for sleep quality all year round. Enjoy.
On a usual Saturday, you wouldn't find me here. And I mean, of course, I don't give TEDx talks every Saturday. But what I mean is, you probably wouldn't find me in a museum. Father, if you were looking for me, you'd probably have to go to the mountains. And that is because I absolutely love hiking.
Chapter 2: How does our internal biological clock synchronize with daylight?
And in addition to just being outside and being in the nature, what I really like is this feeling of physical exhaustion, sort of this satisfaction you can feel in every single muscle. And in the evening, when it's time to go to bed, I absolutely cherish this amazing sleepiness that fills you from head to toe. Now, you might say, well, of course she's tired. She's been hiking all day.
Plus, not to forget about the effects of supposedly fresh air. But there is one factor that most likely outweighs the effects of fresh air, and perhaps even physical activity, and that is exposure to natural daylight. And today, I hope to convince you that we should all appreciate daylight as sort of a natural soporific.
And hopefully, by the end of the talk, you will also recognize that we should all pay more attention to our daily light diet. But let's start with the question why daylight is so important for our organism, for health, and eventually for sleep. Now, throughout your body, in each and every single cell, there is a tiny molecular clock ticking inside it.
And to keep these millions of clocks in sync, we have one central body clock that is located in the brain in an area which we call the hypothalamus. And like the conductor of an orchestra, it communicates the time of day to each of these molecular clocks.
Chapter 3: What types of light receptors are important for our sleep?
And this way, it is able to regulate bodily processes in sync with the time of day. For example, it causes your body temperature to increase in the morning and to decrease in the evening. It choreographs the release of certain hormones at appropriate times. And in the evening, when it's time to go to bed, it will also make you tired and sleepy.
But given this precise synchronization between internal or biological time and external time or even environmental time, it seems clear that the body clock cannot be blind or isolated or shut off from the environment, but rather it needs to receive information about the time of day from the environment for it to synchronize with sun time.
And this is achieved by close connections between the internal biological clock in the brain and our eyes. And now you may know that in the human retina, there are different types of receptors, photoreceptors, so receptors that sense light. And classically, we distinguish two types, the rods and the cones. But this is not the whole story.
because only fairly recently, only in the early 2000s, another type of cell has been discovered, and we call them retinal ganglion cells. These cells do not contribute to a visual impression, but they're exclusively designed to sense short wavelength proportions in daylight. Sometimes we also call this blue light.
Chapter 4: How much natural light do we need for better sleep?
So they're designed to extract important information about the time of day from the environment and pass this on to the internal biological clock in the brain. And I guess you've all experienced how well this biological timing system, this connection between our biological clock and the external world or our eyes, works. When we, for example, travel across time zones,
Now, how much light do we actually need? How much light is enough for the positive effects on, for instance, sleep to occur? And I have to admit, this is not so easy to answer. But I think what we have to keep in mind is that the biological timing system has evolved under the open sky and not in offices or museums. So it is also optimally tuned to the conditions we find outside.
Office light or light in rooms is in no way comparable to what we find outside. And therefore, from a scientific perspective, I can only recommend you to spend as much time as you can under the open sky, but try to make it at least 30 minutes per day. Now, let's finally talk about sleep. And I've repeatedly alluded to the fact that daylight is beneficial and important for sleep.
Chapter 5: Why is daylight exposure crucial for sleep quality?
And in this context, I'd like to share a little story. So last year, I had to go to hospital for surgery. And generally, the hospital environment is a very challenging one for sleep. Because you spend way too much time in bed, not moving much. You might be in pain. Now and then someone comes in to check on you, even during the night. And if you're as lucky as I was, you have a snoring roommate.
And because you, of course, don't get a lot of daylight. And that's why many people, while they're in hospital, ask for sleep medication. But as I consider myself to be a generally good sleeper, and also because I know how these drugs work, I didn't want this. But I knew there was something I could do to help my body sleep as well as possible, even in this situation.
And that was to maximise exposure to daylight.
Chapter 6: What practical steps can we take to maximize daylight exposure?
Because as a sleep scientist, of course I know about the research findings. I know that the more daylight that you get, the more tired you will be in the evening, the easier it will be for you to fall asleep, and the better the experience of sleep quality.
And in addition, daylight exposure has also been shown to increase proportions of deep sleep, which again has been linked to processes of tissue repair. Something not to be underestimated after surgery. And beyond the effects on sleep, we know that patients in brighter rooms experience less pain and less stress. And also, the effects of daylight on mood are well established.
So I thought it might be time for me to put into practice what I often preach. And I have to confess that usually I'm much better at giving advice than following it myself. But here's what I did.
So first, when it became free, I asked the nurses to move my bed to the window place, because that does not only give you power of the fresh air supply, which is highly recommended in the hospital, but it also maximizes daylight exposure, even though you're inside. Second, as soon as I could leave my bed again, I went to the park for short walks.
And last, every meal I had, I tried to take on the little balcony.
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Chapter 7: How can we implement daylight strategies in challenging environments?
Did it work? Well, that's a bit difficult to say because it, of course, was a single-case study. But from patients suffering from insomnia, so one of the most common sleep disorders, we know that light therapy is beneficial.
And therefore, I would like to encourage all of you, and perhaps especially those who might belong to the 25% suffering from sleep problems, to start your own single case study. Thank you.
That was Christine Bloom at TEDxBasil in 2022. If you're curious about TED's curation, find out more at TED.com slash curation guidelines. And that's it for today. TED Talks Daily is part of the TED Audio Collective. This episode was produced and edited by our team, Martha Estefanos, Oliver Friedman, Brian Green, Autumn Thompson, and Alejandra Salazar. It was mixed by Christopher Faisy-Bogan.
Additional support from Emma Taubner and Daniela Balarezo. I'm Elise Hu. I'll be back tomorrow with a fresh idea for your feet. Thanks for listening.
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