The Lehigh Valley Health Network narcolepsy cohort: clinical and polysomnographic analysis of 304 cases.

Abstract

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 versus 27.4 years, p=0.03), shorter diagnostic gap (3.0 versus 4.6 years, p=0.002), more frequent sleep paralysis (55.8% versus 19.4%, p<0.0001) and hypnagogic hallucinations (46.2% versus 25.4%, p=0.003), and higher Epworth Sleepiness Scale (ESS) scores (17.8 versus 16.7, p=0.02). 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%) versus 94 (37.3%), p=0.05]. On the Multiple Sleep Latency Test, patients with NT1 had more sleep onset REM periods (SOREMPs) than patients with NT2 (≥3 SOREMPs in 59.2% versus 26.9%, p<0.0001). Only in NT2, hypnagogic hallucinations and higher ESS scores were associated with higher numbers of SOREMPs (p=0.0277 and p=0.0179 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.