Abstract Introduction Sleep inertia (characterized by profound difficulty waking up with grogginess, disorientation, and cognitive impairment immediately after awakening) is a core idiopathic hypersomnia symptom and may also be experienced by individuals with narcolepsy. Sleep inertia in individuals with narcolepsy is not well studied. This post-hoc analysis of the DUET study (NCT05875974) evaluated sleep inertia in narcolepsy type 1 (NT1) and narcolepsy type 2 (NT2) subgroups of the DUET narcolepsy cohort. Methods DUET was a phase 4, prospective, open-label study with baseline (BL), titration/optimization, stable-dose, and end-of-treatment (EOT) periods. Exploratory outcomes included Psychomotor Vigilance Test (PVT; objective performance impairment) and Karolinska Sleepiness Scale (KSS; subjective sleepiness); both administered at BL and EOT, in the morning after overnight polysomnogram. The 10-minute PVT was completed at 10, 40, and 90 minutes after awakening. The KSS, a single-item, 9-point scale, was completed upon awakening and immediately before and after the PVT assessments. Separate nonlinear, mixed-effects regression models were applied to PVT lapses and KSS ratings to estimate objective and subjective sleep inertia magnitudes, respectively, for NT1 and NT2, along with sleep inertia dissipation time constants for the overall cohort. Treatment-emergent adverse events (TEAEs) were assessed. Results Of 55 enrolled participants with narcolepsy, 26 and 29 had NT1 and NT2, respectively. Most (NT1/NT2) were female (73.1%/72.4%) and White (73.1%/86.2%); 16/26 and 18/29 completed the study. Based on PVT lapses, objective sleep inertia ±SE (NT1/NT2) at BL was 33.1±6.2/14.9±3.2, and at EOT was 8.3±1.7/3.2±1.1 (BL-to-EOT changes 95% CI: −24.8 −35.5, −14.1 and −11.8 −17.4, −6.1). Based on KSS ratings, subjective sleep inertia ±SE (NT1/NT2) at BL was 1.1±0.6/1.1±0.5, and at EOT was 0.8±0.5/1.3±0.5 (BL-to-EOT changes 95% CI: −0.3 −1.9, 1.2 and 0.2 −1.3, 1.6). Sleep inertia dissipation time constants ±SE were 1.6±0.3h (PVT) and 0.4±0.1h (KSS) for the overall cohort. TEAEs were consistent with the known LXB safety profile. Conclusion Participants with narcolepsy, especially NT1, demonstrated objective sleep inertia at BL. Participants with NT1 or NT2 showed substantial improvements in objective sleep inertia with LXB treatment. Support (if any) Jazz Pharmaceuticals
Nichols et al. (2026) studied this question.