how long should i spend in each sleep stage
Usually, REM sleep happens 90 minutes after you fall asleep. The first period of REM typically lasts 10 minutes. Each of your later REM stages gets longer, and the final one may last up to an hour. Your heart rate and breathing quickens. You can have intense dreams during REM sleep, since your brain is more active. Babies can spend up to 50% of their sleep in the REM stage, compared to only about 20% for adults.