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It blows my mind (pun intended?) that we still don't really know why we need sleep, even though we sleep for like 20% of our lives.

We know some stuff, like if you don't sleep, bad stuff happens to your body and you don't form memories effectively, but like the article says we haven't figured out why it's so essential.

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20% (4.8 hrs)? I don't know about you, but for me it's closer to 33%.

Haha ya, I guess that's really on the low end. I was thinking of old people who seem to sleep like 4 hours a night for the last 20 years of their lives. Plus people are generally sleep deprived.

Old people pretty much are sleep deprived, though. Their systems are falling apart (that's aging). I was reading a study once on, I think, melatonin in the elderly, and it showed a graph of the 24-hour melatonin secretion cycle for a young healthy sample and then for like age 60+ people; in the young people, the cycle looks exactly as one would expect, with a fall in mid-day, increase in evening, and high levels while asleep during the night and slowly declining to the day levels - in the elderly, it was a flat line. Horrifying.

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