Why some people need less sleep than others

HostMost of us know that feeling when the alarm goes off and it feels like a physical blow. We spend our mornings in a fog, just waiting for the coffee to kick in so we can finally join the land of the living. But then you meet those rare people who seem to thrive on four or five hours of sleep every single night without a single yawn. Is that something they just forced themselves to do, or is something different actually happening in their bodies?

GuestIt's a real thing, though it's very rare. For a long time, many experts thought these people were just lying to themselves or pushing through the day on pure stress. But when you bring them into a lab, you see something much more interesting. They're not just getting by. They're wide awake, they're sharp, and they don't show any of the signs of being tired that we would expect. They're called natural short sleepers. It's not a habit they learned; it's how they're built from the day they're born. Their brains seem to be much more effective at the work sleep is supposed to do. You can think of sleep like a cleaning crew that comes into an office building at night. For most of us, that crew needs eight hours to mop the floors and empty the trash. For these people, the crew is twice as fast and much better at the job.

HostSo their brain is basically doing more work in less time. But how does that work? Do they just skip the parts of sleep that aren't as useful?

GuestThat's what's so strange. They don't skip the deep sleep. In fact, they seem to get right to it. Most of us might toss and turn or spend a long time in light sleep before we hit the good stuff. These short sleepers dive straight into the most refreshing stages. We have found a specific change in a gene that seems to be the key. When scientists put this same gene change into mice, those mice needed way less sleep too. They also recovered from being kept awake much faster than normal mice. It's like their internal battery charges at double speed.

HostI have tried to get by on four hours before, and by noon the next day, I can barely remember my own name. If these people are only sleeping half as much as I do, why don't they have that same brain fog?

GuestBecause their brains are better at clearing out the junk. During the day, our brain cells use energy and create waste. If that waste builds up, it makes us feel slow and groggy. Usually, the brain flushes that waste out while we sleep. In short sleepers, this trash pickup system is just incredibly high-powered. They don't have the buildup because their brain is so good at the wash cycle. And because they don't have that buildup, they don't get the mood swings or the memory slips that we get. They actually tend to be very upbeat. Many of them have a very specific type of personality. They're often unusually cheerful, energetic, and driven, even after a long day.

HostThat sounds a bit too good to be true. I’ve always heard that if you don’t sleep enough, your heart suffers or you gain weight. Is there no health catch for these people?

GuestThat's the part that feels a bit unfair. In most people, sleeping less than seven hours is linked to high blood pressure and a higher risk of heart problems. But these natural short sleepers seem to be shielded from those health issues. Their bodies aren't under stress from the lack of sleep because, for them, it's not a lack. They're getting exactly what they need. There was a study on two sisters who were both short sleepers. They were in their 70s and 80s and were in great health. They had been sleeping four hours a night their whole lives. Their bodies just didn't show the wear and tear we would expect.

HostBut plenty of people brag about only needing five hours of sleep. Are they all part of this lucky group, or are they just fueling themselves with caffeine?

GuestMost of them are likely just fueling themselves with coffee and willpower. There's a huge difference between a true short sleeper and someone who's just sleep deprived. True short sleepers are very rare. Maybe about one out of every hundred people who say they only need five hours are actually built that way. The rest of us are just running on fumes. We have become so used to being tired that we think it's normal. We think we're doing fine, but if you tested how fast we could react, we would do as poorly as someone who had been drinking. True short sleepers don't have that drop-off. They're just as sharp at the end of the day as they were at the start.

HostIt's tempting to try and train myself to be like them. If I just slowly cut back my sleep every week, could I get my brain to be that fast?

GuestNo. It's pretty much set in your DNA. Trying to force it's like trying to train your body to not need water. You might be able to ignore the thirst for a while, but your organs are still going to suffer. When people try to hack their sleep to be like these folks, they usually just end up with a massive sleep debt. That debt has to be paid back, or it starts to damage your health and your brain. These people don't have that debt because their bodies never needed the extra time in the first place.

HostIt's a total shift in how we think about the human body. If you gain three or four hours every single day, over a lifetime, that's years of extra waking time.

GuestIt adds up to about sixty days of extra time every year. That's two whole months. And they use it. They often have three or four hobbies, they work long hours, and they stay very active. They show us that the quality of the sleep matters way more than how long you stay in bed.

HostOne of the weirdest things scientists found is that these short sleepers often stay busy and upbeat right until the moment they hit the pillow, without any of the slow wind-down the rest of us need.

GuestThe dream of getting an extra four hours of life every single day stays just out of reach for the rest of us who still need that long, slow wash.