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Comment by agentultra | Hacker News Reader

Sleep is weird. If I wake up in the middle of the night and go back to sleep... I feel like ass the next day. If I get less than eight hours I'm pretty tired the next day.

But science says that shouldn't happen!?

Not enough evidence to suggest that there's any kind of regularity to how humans "should" sleep yet.

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It is even more weird than that. From my and some friend's experience: if you sleep more then 9 hours straight, instead of usual 6-8 (this happens on weekends usually), I feel really terrible in the morning - not being able to get out of bed, but in the same time not being able to sleep. Finally when I get out of bed - I feel really trashed for next several hours.

So it is not just less than 8 hours makes things worse, same applies to more then 8 hours. So it is either I have to sleep 6-8 hours only, or I have adapted to this schedule so well, that anything else makes me feel terrible.

On the other hand, I have handful examples of me traveling with few flight changes, timezones changes, more than 30 hours in flights/airports, and after getting to my destination I spent full 16 hours day working or meeting with friends just fine. May be a little dizzy. And after consequent 8 hours sleep night - feel great next day.

This suggest, that it (8 hours sleep requirement) is more than just a something "hardwired" in to human's body...

Yes, sleep is weird.

This is why, I find that getting up at the same time on the weekend as I do during the work week actually helps keep my sleep patterns somewhat regular. So, although the idea of an occasional Saturday morning sleep-in sounds good, in practic, I'm better off getting up at my usual 4:45am every day and supplementing with a short nap after lunch if necessary.

Often when you wake up after sleeping longer than usual (say more than 9 hours) you feel tired because of dehydration. Your body loses a fair bit of water while you sleep, so that might be reason you feel bad after a lie-in.

I have anecdote to confirm this. I stay well hydrated, and drink more water than most people I know, will generally sip on a glass by my bed, and have a glass of water by my bed at night. I have also been able to sleep over 12 hours (generally waking up at least once to use the restroom and water) Yet I feel fantastic when I do such!

> If I wake up in the middle of the night and go back to sleep... I feel like ass the next day.

If you wake up because you have to, or if you just happen to wake up in the middle of the night naturally?

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