Prolonged sleep deprivation can lead to severe health problems in humans and other animals. But why is sleep so vital to our health? A UCLA-led team of scientists has answered this question and shown for the first time that a dramatic change in the purpose of sleep occurs at the age of about 2-and-a-half.
The data were remarkably consistent: All species experienced a dramatic decline in REM sleep when they reached the human developmental equivalent of about 2-and-half years of age. The fraction of time spent in REM sleep before and after that point was roughly the same, whether the researchers studied rabbits, rats, pigs or humans.