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  • Late sleepers get a bad rap.

  • Rise and shine! Come on!

  • Maybe your friend who wakes up at 5 a.m. every day is kind of quirky, but I bet they're productive.

  • Your friend who wakes up at 11 every day, what do you think about them?

  • But it turns out, sleeping late isn't just a preference or a bad habit.

  • Research is showing that our bedtime could be coded into our DNA.

  • Each of us has an internal clock, but my clock isn't necessarily in sync with yours.

  • That's because we all have our own chronotype, or preferred sleeping pattern.

  • Scientists study chronotypes by tracking when people go to sleep on days when they don't have to go to work or to school.

  • This chart shows the mid-point of people's sleep on those free days.

  • If you go to bed around 11 p.m. and get up around 7 a.m., you have an average chronotype.

  • A very small number of people on either end of the chart have either very early or very late chronotypes.

  • But even those of us who are just slightly behind the average chronotype can wake up feeling jet-lagged every day.

  • If you have an average chronotype, you're generally getting the same amount of sleep on both free days and work days.

  • So your sleep schedule fits with society's schedule.

  • But the later your chronotype, the bigger the difference between the amount of sleep you get on free days versus work days.

  • So going back to a work after a free day can feel like flying over several time zones.

  • And to understand why, you need to look at the master clock in our body.

  • It's a bundle of neurons called the Suprachiasmatic Nucleus, or SCN.

  • If you have a normal chronotype, your SCN tells the pineal gland to start producing melatonin around 9 p.m., that makes you sleepy.

  • Around 10:30, your colon starts suppressing bowel movements.

  • Your body temperature drops to its lowest point around 4:30 a.m., and your blood pressure reaches its highest point around 6:45 a.m., so you're at your most alert around 10 a.m..

  • But for people with late chronotypes, all this stuff happens later in the day. And there's not much they can do about it.

  • That's because inside the neurons that make up the SCN, scientists have discovered something called clock genes.

  • These genes turn on and off throughout the day to keep your body on a this 24-hour cycle.

  • This 7 day time-lapse of the SCN shows these clock genes releasing proteins every 24 hours like clockwork.

  • Researchers who study families of extreme early-risers show that many of them share the same mutation on one of these clock genes, and studies have found similar mutations in hamsters with early chronotypes.

  • But when scientists took out these hamsters' SCN, their body clock, and replaced them with the SCN of a normal hamster, they still woke up and went to sleep super early.

  • That's because the SCN isn't our only biological clock.

  • You also have all these little clocks in every single cell of your body.

  • In the early-rising hamsters, these clocks in the body preserved the early chronotype, even after the brain's SCN was taken out.

  • And for humans, this helps explain why it's nearly impossible for late sleepers to adjust to society's schedule.

  • The cells in their bodies literally won't let them. And that's a problem.

  • In one study, researchers took healthy people and messed with their sleep schedules.

  • After three weeks, they had early signs of diabetes.

  • People with late chronotypes are also more likely to be smokers and to develop depression.

  • And maybe that should change the way we think about sleep, you know, it's not this nuisance, it's this kind of fundamental part of life.

  • Maybe some late sleepers are lazy, sure. But the rest have been sorely misunderstood.

Late sleepers get a bad rap.

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B1 US Vox chronotype clock sleep early body

Late sleeper? Blame your genes.

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    Jacky Avocado Tao posted on 2016/08/01
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