DAVE ASPREY: One of the biggest things you can do that isn't going to cost you anything is improve the quality of your sleep. It's funny, because when you get a good night's sleep regularly at the right time, your risk of cancer drops dramatically. Conversely, if you are a shift worker or you regularly fly all over the place and you don't take care of your biology, your chances of cancer go up a lot. One night of bad quality sleep can change your ability to regulate your blood sugar by up to 40%. Now, that's the path to diabetes. And what about Alzheimer's disease? People who don't get enough sleep and don't regulate their blood sugar also have problems with Alzheimer's disease. And the list goes on. So sleep is a foundational element. And if you really think about it, you can go three, four days without water maybe. You can go a month without food. But try and go three or four days without sleep. It's at least as important as water. But you don't see people going on water diets very often, but you do see people who just don't get enough sleep all the time. This is one of the primary anti-aging things.

But the problem with sleep is that, actually, a lot of people don't have time for sleep. And it's OK to not have time to sleep, because you have a job, you have a family, you have a social life, and you have stuff you wanted to do. So what are you going to do? Are you going to choose to die earlier or to get sleep? Or maybe there's a better way. And in Super Human, I talk about sleep hacking. And here's an example. I landed in New York last night, and I flew from the west coast from Seattle. Now, that's a recipe for a terrible sleep, for jet lag. But I changed the amount and the color of light that I allowed into my eyes on the airplane using patented glasses that I created called TrueDark. And in fact, if I look at my phone here, I track my sleep with a ring. It gives me a very detailed analysis. And I'll tell you my real numbers from last night. I didn't get as much sleep as I would have liked. But what I did get was five hours and 23 minutes of sleep. I didn't get to my hotel until 1:00 in the morning. And I was traveling with one of my kids. But I got two hours and 11 minutes of deep sleep. That's more deep sleep than a 20-year-old gets an eight hours. And I got 58 minutes of dreaming sleep. So I got better sleep than most Americans get on most nights even though I flew in the wrong direction three hours and was sleeping in a foreign environment. How the heck do you do that?

Well, the biggest thing is to turn the lights down at night. Just dimming your lights, turning off the bright white stuff in your kitchen and your bathroom after the sun goes down, it doesn't change the length you'll sleep necessarily, but it changes the quality of your sleep. And since I couldn't do that on the airplane or in the hotel room, I wore glasses that took out the bright colors, the blue light. And you go back to the '50s: We had incandescent bulbs, and not that many of them, and they weren't that bright. Now that we have these fluorescent lights and LED lights, we can have incredibly bright light right before bed. In fact, most of us do. And that sends a signal to the ancient parts of our body, sub-cellular things that control our aging and control how our body responds to the environment -- they're called mitochondria -- and inside your eyes, about 5% of your cells are melanopsin sensors. And these collect light. And you never see that light. It doesn't go into your visual cortex. It bypasses that, and it's just the timing signal. And if you're a computer scientist or a computer hacker guy, like I am, you understand that computing relies on a clock. So for this server over here and this server over here to do something, they both need to know what time it is, down to the microsecond. For all of the quadrillion cells in your body to do what they're supposed to do, they all need to know what time it is. And that's why every organ has a clock. That's why each cell has a clock. And that's why the master clock is stored in something called the SCN inside the brain. And light controls the SCN more than anything else. So does food intake, to a certain point.

So here's the deal. Don't eat after the sun goes down, turn the lights down as much as you can after the sun goes down, and black out your room. You could say, 'Really, I have to black out my room? I have blackout curtains.' Check this out. A study from Japan -- 68% increase in depression when people slept with the amount of light that comes around blackout curtains in a normal city. It doesn't take very much light at night in order to screw up the quality of your sleep and then the quality of your thinking. This was a study of about 800 men, so presumably, it's the same for women, or maybe even worse. And they were older. They were over 60. So maybe if you're 25, you can sleep in bright light, I just don't recommend it, because all the data we have say your risk of dying of everything goes up if you sleep in a brightly lit, noisy room. Eight hours doesn't matter. It's the quality of those eight hours that matters.

The flip side of darkness is, obviously, light. So what's light going to do for you? It turns out, if you want to sleep well at night, when you wake up in the morning, go outside, take off your glasses, take off your sunglasses, even take out your contacts, and just get 20 minutes of bright sunlight. And if, like me, you live far north -- I'm in Canada -- there's sometimes just isn't sunlight, so I actually use a sun lamp or really, really bright indoor lighting -- halogen lighting, though -- stuff that is rich and warm. In fact, even a little bit of ultraviolet light is good for you. It's good for your skin. It's good for your eyes. It's good for your brain. Too much of it isn't good for you. In fact, it can increase your risk of skin cancer if you're getting sunburns. But no sunlight on your skin, no sunlight in your eyes without protective glasses and things like that is not a good strategy to live a long time or even feel very good.

We all know about seasonal affective depression and the idea that some people get the winter blues. But it turns out you can give yourself the winter blues if you wear sunglasses outdoors all the time all summer long. So just make it a point. Wake up in the morning, go for a walk, open the window, and just look at some natural sunlight. And the reason this works is that that timing system in the body is looking for that. And if you give it the bright light, especially in the evening, it says, I don't know what time it is. And then all the different systems in the body that are supposed to work as a system in unison, they don't do that. And that's what leads you down that path of diabetes, cancer, and Alzheimer's.