Julie Flygare said this quote
“ Normally, it takes people about 60 to 90 minutes to reach REM sleep, so they wouldn’t enter this stage during a 20 minute nap. People with narcolepsy often enter REM sleep soon after falling asleep. If a person enters REM sleep in two or more of the five naps in eight minutes or less during the study, it’s highly suggestive of narcolepsy. ”