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Comment by kombinar | Hacker News Reader

Interesting. I found after some trail and error that I'm more rested and perform better on less than recommended 8h of sleep. My sweet spot is somewhere around 7h. Fitbit "magic" sleep score also seems to confirm that (better sleep score on less sleep). I also found that stress is the biggest factor in getting good night sleep. When stressed I can sleep 8h and still feel bleh.

I wonder if 8h of sleep is the cause of the better performance or they both are a result of less stressful life, better health or something else.

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I've been sleeping approximately 9:30 to 4 and feel way better. Groggy upon waking up, but okay by 4:30, getting stuff done. Feels like there's a lot more time in the day. Probably because late nights were mostly wasted time eating junk food anyway. Allow myself some catch up sleep on the weekends, and it seems to work out.

It was hard at first but now that I am used to it, I'm hooked.

> I wonder if 8h of sleep is the cause of the better performance or they both are a result of less stressful life, better health or something else.

This illustrates well the problem with these kinds of studies. How do we know that stress isn't causing both little/poor sleep and e.g. decreased cognitive performance (as opposed to little sleep being the cause of a decrease in cognitive performance)?

It's not like we can create a control group where stressed people are forced to get 8 hours of good sleep every night.

We can actually. That is what sleep labs are for. I don't know if this exact setup has been done, but there is a lot of stuff like making people cram for an exam and then varying their sleep opportunity.

If you mean that you cannot literally make people sleep: No, but you can manipulate consistently by just setting sleep opportunity and then measure the actual sleep time on top of that to draw conclusions.

The amount of sleep required depends on the person and their living situation.

I normally feel best on 7-8 hours of sleep. When training hard I require 9 hours.

There are genetic outliers who require less sleep (google it).

Anecdotally: I have a friend who performs like anyone else, but only requires around 5-6 hours of sleep. I've known him for over a decade now, he seems to be doing fine.

I just watched Iron Lady last night and Margaret Thatcher slept 4 hours a night almost every night for her entire life, and lived well into her 80s.

She also got dementia. There is some evidence that lack of sleep contributes to the development of Alzheimer's and dementia.

I've found that if I'm fully caught up on sleep, 7 hours is what I naturally sleep. However if I'm behind (slept less then 7 hours for multiple days) then I will sleep random amounts until I get back into a routine.

I've settled for somewhere around 7.5h as I find this is less likely to lead to sleep onset or maintenance issues. Trouble falling asleep can shrink the total time even more, so I like to avoid that risk.

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