Change in mean sleep latency time (in minutes) as determined from the first 4 trials of a 40-minute MWT from baseline to Week 12. MWT sleep latency ranges from 0 to 40 minutes, with higher scores indicating greater ability to stay awake; a positive change from baseline represents improvement in the sleep latency time. Mean sleep latency defined as the average of the first 4 MWT trials, if 3 or 4 of them are non-missing.

Change in Epworth Sleepiness Scale (ESS) score from Baseline to Week 12. A negative change from baseline represents improvement in excessive sleepiness. The ESS is a self-administered questionnaire with 8 questions. Each activity is scored on a scale ranging from 0-3, with 0 = would never fall asleep, and 3 = high chance of falling asleep. The total score ranges from 0-24, with a higher number representing an increased propensity for sleepiness. An analysis of covariance (ANCOVA) was used for the analysis of ESS scores. The response variable was the change in ESS score from baseline.

Change in Epworth Sleepiness Scale (ESS) score during the 2-week randomized withdrawal period. The beginning of the randomized withdrawal period represents efficacy baseline. A negative change from baseline represents improvement in excessive sleepiness. The ESS is a self-administered questionnaire with 8 questions. Each activity is scored on a scale ranging from 0-3, with 0 = would never fall asleep, and 3 = high chance of falling asleep. The total score ranges from 0-24, with a higher number representing an increased propensity for sleepiness. An analysis of covariance (ANCOVA) was used for the analysis of ESS scores. This analysis included treatment group and randomization stratification factor (narcolepsy vs. OSA) as fixed effects. The ESS score at the beginning of the randomized withdrawal period was used as the covariate. The response variable was the change in ESS score from the beginning to the end of 2- week randomized withdrawal period.

Subjects were instructed to drive with steady lateral position between the delineated boundaries of the slower (right) traffic lane, while maintaining a constant speed of 95 kilometers (km) per hour (hr). Deviation was measured by the vehicle's speed and lateral distance to the left lane line and was continuously recorded. Individual improvement was defined as a decrease in SDLP below the negative value of threshold; individual impairment was defined as an increase in SDLP above the threshold or failure to complete the driving test due to sleepiness or subjects related safety concerns.