A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
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The human brain is more active during sleep than during the day.
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The record for the longest scientifically documented period without sleep is 264.4 hours (eleven days).
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One reason that kittens sleep so much is because a growth hormone is released only during sleep.
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The harder you concentrate on falling asleep, the less likely you are to fall asleep.
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"Dysania" is the state of finding it hard getting up out of bed in the morning.
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There's a love mattress that is specifically designed for couples who sleep on each other's arms.
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In China, teachers allow children to sleep in class for around 20 minutes to help improve their learning.
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