Young and middle-aged adults
At the age of 20 years the sleep ef?ciency is still usually around 95%, but it then falls progressively. By 35 years the duration of stage 4 NREM sleep is only around 6% of the total sleep time which is only half of what it is at 20. Wakefulness at night is twice as prolonged and the duration of stage 1 NREM sleep is increased slightly at around 5% of total sleep time. The percentage of REM sleep remains constant at around 22–25% throughout early and middle adult life, but REM density gradually falls. Changes in (more…)
