The Lehigh Valley Health Network Narcolepsy Cohort: clinical and polysomnographic analysis of 304 cases

Study objective: We aimed to characterize clinical features, comorbidities, and polysomnographic characteristics of a large cohort of patients with narcolepsy. Methods: We undertook a retrospective chart and polysomnographic review of all patients with a diagnosis of narcolepsy type 1 (NT1) or narcolepsy type 2 (NT2) seen within the Lehigh Valley Health Network between 2000 and 2022. Results: We found 304 cases with a diagnosis of narcolepsy (52 NT1, 252 NT2), based on International Classification of Sleep Disorders, third edition criteria. Compared to NT2, patients with NT1 had younger diagnosis age (24.5 vs 27.4 years, P = .03), shorter diagnostic gap (3.0 vs 4.6 years, P = .002), more frequent sleep paralysis (55.8% vs 19.4%, P < .0001) and hypnagogic hallucinations (46.2% vs 25.4%, P = .003), and higher Epworth Sleepiness Scale scores (17.8 vs 16.7, P = .02). The most common comorbid sleep disorders were breathing disorders (17.4%) and insomnia (15.5%). Migraine was the most common neurological disorder. Depression was more common in NT2 than NT1 (12 [23.1%] vs 94 [37.3%], P = .05). On the Multiple Sleep Latency Test, patients with NT1 had more sleep onset rapid eye movement periods than patients with NT2 (>= 3 sleep onset rapid eye movement periods in 59.2% vs 26.9%, P < .0001). Only in NT2, hypnagogic hallucinations and higher Epworth Sleepiness Scale scores were associated with higher numbers of sleep onset rapid eye movement periods (P = .0277 and P = .0179, respectively). Conclusion: This is one of the largest monocentric studies to date of patients with narcolepsy and confirms the frequent comorbidities of narcolepsy. Specific clinical characteristics and comorbidities may help differentiate NT1 from NT2.