Clinical and Neuropsychological Data on Narcolepsy Shows No Difference in Comparison of Global Networks

Claudio L.A. Bassetti, MD, PhD

A recently published study (NCT05375890) in the Journal of Clinical Sleep Medicine showed nonsignificant differences in clinical and neuropsychological data in the Russian Narcolepsy Network (RN-NN) relative to that previously reported in the European Narcolepsy Network (EU-NN).¹ The findings showed more severe and higher percentages of patients who experience cataplexy in Russia, suggesting a low awareness of narcolepsy.

Comparing data with the EU-NN,² the RN-NN had fewer patients with excessive daytime sleepiness (EDS) as a first symptom (25.6% vs 43.8%; P = .0014), whereas the percentage of both EDS and cataplexy as a first symptom was almost twice as high as in the EU-NN data (67.4% vs 48.8; P = .0013). Notably, the prevalence of severe cataplexy cases was higher in the RN-NN than in the EU-NN data (93.8% [n = 80] vs 62.6% [n = 829] in EU-NN; P = .001).

Senior author Claudio L.A. Bassetti, MD, PhD, professor of neurology and vice-dean of the medical faculty at the University of Bern, and colleagues wrote, “We suggest that the lack of reliable information about their disease and the suspicion that they have a serious neurological pathology lead the patient to restrictions in daily life including social contacts, which are accompanied by distress, emotional overeating, and a decrease in physical activity.”¹

Participants were recruited from 11 sleep centers in Russia and were given a questionnaire of 58 questions to complete in terms of demographic, clinical, polysomnography (PSG), and multiple sleep latency test (MSLT) data. The mean age of patients was 35.6 (±16.9) years (men, 58%; women, 42%), and mean age of narcolepsy onset was 25.6 (±14.6 years (range, 5-74 years). The average Epworth Sleepiness Scale score for patients was 18.4 (±3.5 points; range, 11-24).

Among the participants (n = 80), more than 90% had frequent or very frequent cataplexy attacks and none had very rare cataplexy attacks. Hypnagogic or hypnopompic hallucinations were experienced (n = 73) in 82% of patients, while 59.1% (n= 52) experienced sleep paralysis, and 55.7% experienced both symptoms present (n = 49). The mean sleep latency during MSLT in 52 patients without treatment was 5.0 (±3.0) minutes; 88.5% had a sleep latency of less than 8 minutes. The mean percentage of sleep-onset rapid eye movement (REM) periods (SOREMPs) during the MSLT was 58.9% (±22.9%).

Compared with EU-NN, sleep paralysis (59.1%, n = 88) and hallucinations (82.0%, n = 89; P = .0017) were present in the RN-NN more often than in the European cohort (52.6% [n = 257] and 63.1% [n = 370], respectively). Data with PSG and MSLT in RN-NN are similar, although the mean sleep latency in MSLT (4.9 [±2.9] minutes [n = 52] vs 3.9 ± 3.0 minutes [n = 927]; P = .0193) was observed as higher in the Russian cohort.

“In this study we, for the first time, described the clinical picture of NC in Russian patients, which will draw the attention of local doctors to this problem. Despite the limited availability of PSG and MSLT and the inaccessibility of cerebrospinal fluid orexin level, the comparability of the clinical characteristics of the Russian cohort allows using our data together with the European data,” Bassetti et al noted.¹

Bassetti et al wrote, “The results of the study, which demonstrated the prevalence of severe forms of cataplexy in the Russian population compared with the European one, confirm the validity of prescribing anti-cataplectic drugs.”¹

Investigators noted the limitations of the study including that the overall number of cases for patients with narcolepsy was low. Additionally, the human leukocyte antigen typing and assessment of orexin in the cerebrospinal fluid were not available. Only 55 of 89 patients underwent MSLT and only data from patients with narcolepsy-cataplexy were used in the analysis. Notably, there were no conclusions drawn on pathophysiology because of data collection solely based on clinical and demographic characteristics.

“It is clear that there is no Russian national narcolepsy control system, especially at the level of early detection. The small number of patients whom we recruited during almost 5 years of the study again highlights the low awareness of doctors about NC and the importance of more thorough screening algorithms. Our study is the first attempt of the initiative to create a national center for narcolepsy supported by the RU-NN that will drive investigation of narcolepsy in Russia, engaging both professional and patient societies and using modern world knowledge and methods with the cooperation of the EU-NN,” Bassetti et al noted.¹

REFERENCES
1. Kuts A, Poluektov M, Zakharov A, et al. Clinical and neurophysiological characteristics of 89 patients with narcolepsy and cataplexy from the Russian Narcolepsy Network. J Clin Sleep Med. 2023;19(2):355-359. doi:10.5664/jcsm.10340
2. Luca G, Haba-Rubio J, Dauvilliers Y, et al. Clinical, polysomnographic and genome-wide association analyses of narcolepsy with cataplexy: a European Narcolepsy Network study. J Sleep Res. 2013;22(5):482-495. doi:10.1111/jsr.12044