Idling for Decades: A European Study on Risk Factors Associated with the Delay Before a Narcolepsy Diagnosis

Zhongxing Zhang,1 Yves Dauvilliers,2– 4 Giuseppe Plazzi,5,6 Geert Mayer,7 Gert Jan Lammers,8,9 Joan Santamaria,10 Markku Partinen,11 Sebastiaan Overeem,12,13 Rafael del Rio Villegas,14 Karel Sonka,15 Rosa Peraita-Adrados,16 Raphaël Heinzer,17 Aleksandra Wierzbicka,18 Birgit Högl,19 Mauro Manconi,20 Eva Feketeova,21 Antonio Martins da Silva,22 Jitka Bušková,23 Claudio LA Bassetti,24,25 Lucie Barateau,2– 4 Fabio Pizza,5,26 Elena Antelmi,5,6 Jari K Gool,8,9 Rolf Fronczek,8,9 Carles Gaig,10 Ramin Khatami1,24 1Center for Sleep Medicine, Sleep Research and Epileptology, Klinik Barmelweid AG, Barmelweid, Aargau, Switzerland; 2Sleep-Wake Disorders Unit, Department of Neurology, Gui-de-Chauliac Hospital, CHU Montpellier, Montpellier, France; 3National Reference Centre for Orphan Diseases, Narcolepsy, Idiopathic Hypersomnia, and Kleine-Levin Syndrome, Montpellier, France; 4Institute for Neurosciences of Montpellier INM, Univ Montpellier, INSERM, Montpellier, France; 5Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy; 6IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy; 7Neurology Department, Hephata Klinik, Schwalmstadt, Germany; 8Sleep Wake Center SEIN Heemstede, Stichting Epilepsie Instellingen Nederland, Heemstede, the Netherlands; 9Department of Neurology and Clinical Neurophysiology, Leiden University Medical Center, Leiden, the Netherlands; 10Neurology Service, Institut de Neurociències Hospital Clínic, University of Barcelona, Barcelona, Spain; 11Helsinki Sleep Clinic, Vitalmed Research Center, Helsinki, Finland; 12Sleep Medicine Center Kempenhaeghe, Heeze, the Netherlands; 13Eindhoven University of Technology, Eindhoven, the Netherlands; 14Neurophysiology and Sleep Disorders Unit, Hospital Vithas Nuestra Señora de América, Madrid, Spain; 15Neurology Department and Centre of Clinical Neurosciences, First Faculty of Medicine, Charles University and General University Hospital, Prague, Czech Republic; 16Sleep and Epilepsy Unit – Clinical Neurophysiology Service, University General Hospital Gregorio Marañón, Research Institute Gregorio Marañón, University Complutense of Madrid, Madrid, Spain; 17Center for Investigation and Research in Sleep, Lausanne University Hospital, Lausanne, Vaud, Switzerland; 18Department of Clinical Neurophysiology, Institute of Psychiatry and Neurology, Warsaw, Poland; 19Neurology Department, Sleep Disorders Clinic, Innsbruck Medical University, Innsbruck, Austria; 20Neurology Department, EOC, Ospedale Regionale di Lugano, Lugano, Ticino, Switzerland; 21Neurology Department, Medical Faculty of P. J. Safarik University, University Hospital of L. Pasteur Kosice, Kosice, Slovak Republic; 22Serviço de Neurofisiologia, Hospital Santo António/Centro Hospitalar Universitário do Porto and UMIB-Instituto Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal; 23Department of Sleep Medicine, National Institute of Mental Health, Klecany, Czech Republic; 24Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; 25Department of Neurology, Sechenov First Moscow State University, Moscow, Russia; 26Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, ItalyCorrespondence: Yves Dauvilliers, National Reference Network for Narcolepsy, Sleep-Disorders Center, Department of Neurology, Hopital Gui de Chauliac, INSERM U1061, Montpellier, UM1, France, Email ydauvilliers@yahoo.fr Ramin Khatami, Center for Sleep Medicine, Sleep Research and Epileptology, Klinik Barmelweid AG, Barmelweid, CH-5017, Switzerland, Email ramin.khatami@barmelweid.chPurpose: Narcolepsy type-1 (NT1) is a rare chronic neurological sleep disorder with excessive daytime sleepiness (EDS) as usual first and cataplexy as pathognomonic symptom. Shortening the NT1 diagnostic delay is the key to reduce disease burden and related low quality of life. Here we investigated the changes of diagnostic delay over the diagnostic years (1990– 2018) and the factors associated with the delay in Europe.Patients and Methods: We analyzed 580 NT1 patients (male: 325, female: 255) from 12 European countries using the European Narcolepsy Network database. We combined machine learning and linear mixed-effect regression to identify factors associated with the delay.Results: The mean age at EDS onset and diagnosis of our patients was 20.9± 11.8 (mean ± standard deviation) and 30.5± 14.9 years old, respectively. Their mean and median diagnostic delay was 9.7± 11.5 and 5.3 (interquartile range: 1.7− 13.2 years) years, respectively. We did not find significant differences in the diagnostic delay over years in either the whole dataset or in individual countries, although the delay showed significant differences in various countries. The number of patients with short (≤ 2-year) and long (≥ 13-year) diagnostic delay equally increased over decades, suggesting that subgroups of NT1 patients with variable disease progression may co-exist. Younger age at cataplexy onset, longer interval between EDS and cataplexy onsets, lower cataplexy frequency, shorter duration of irresistible daytime sleep, lower daytime REM sleep propensity, and being female are associated with longer diagnostic delay.Conclusion: Our findings contrast the results of previous studies reporting shorter delay over time which is confounded by calendar year, because they characterized the changes in diagnostic delay over the symptom onset year. Our study indicates that new strategies such as increasing media attention/awareness and developing new biomarkers are needed to better detect EDS, cataplexy, and changes of nocturnal sleep in narcolepsy, in order to shorten the diagnostic interval.Keywords: cataplexy, diagnostic delay, misdiagnosis, symptom onset, machine learning