Sleep Quality is Much More Important than Quantity

. . . they almost always fell asleep as temperatures began to fall at night, and they would wake up right as the temperatures were rising again.

This suggests that humans may have evolved to sleep during the coldest hours of the day, perhaps as a way to conserve energy, Dr. Siegel said. If falling temperatures at night are a signal to our bodies that it is an ideal time to go to sleep, then that could be one reason chronic insomnia is so prevalent in industrialized societies.

“Today we sleep in environments with fixed temperatures, but none of our ancestors did,” Dr. Siegel said. “We evolved to sleep in a natural environment where the temperature falls at night. Whether we can treat insomnia by putting people in an environment where the temperature is modulated in this way is something to be studied in the future.”

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