Does Narcolepsy that Riki had really exist? At the earlier episodes of little buster. he said that he has an illness called Narcolepsy. Actually, from the beginning of the little buster series, he already in 


   Kyousuke's world where all of his friends died on car accident


So we ca assume that Riki only had his illness, when he got into 


   Kyousuke's World 


But what happen with the Narcolepsy that Riki had before he enters 


   Kyousuke's World ?


Did he still got this illness ?
Riki's parents died when he was around ten years old, leaving him in a state of depression. Around the same time, he was diagnosed with narcolepsy, a disorder causing Riki to uncontrollably lose consciousness at random intervals.
New constructed worlds would be formed again and again, with Riki repeating events, becoming stronger each time.

Taken from Little Buster's Wiki.
It seems to me, that in the beginning he definitely still had narcolepsy, but he might have overcome it at the end through the process of becoming stronger.