Narcolepsy in Slovakia – Epidemiology, clinical and polysomnographic features, comorbid diagnoses: a case-control study

Abstract

ObjectiveAn increase in the incidence of narcolepsy after the pandemic influenza with the H1N1 vaccination in 2009 resulted in an interest in narcolepsy epidemiology. The aim of the study was to examine the incidence and prevalence rates of narcolepsy and to describe the associated characteristics in Slovakia. MethodsEpidemiology data were calculated for each year from 2000 to 2017 based on records found in specialized centres. In sum, 61 narcoleptic patients were diagnosed, of which 51 (84%) had narcolepsy type 1 (NT1). Clinical data and results of polysomnography (PSG), Human Leukocyte Antigen (HLA)-typing, hypocretin (HCRT)-1 levels and body mass index (BMI) were summarised and evaluated for NT1 and narcolepsy type2 (NT2). Later, 244 sex and age matched controls were chosen to evaluate the comorbid diagnoses. ResultsThe prevalence of narcolepsy in 2017 in Slovakia was 10.47 (CI 95% 8.26–14) cases/million inhabitants, and the mean incidence rate (2000–2017) was 0.57 (CI 95% 0.4–0.74) cases/million inhabitants.Narcoleptic patients were comorbid with arterial hypertension (17%), ischemic heart disease (8%), dyslipidaemia (18%), diabetes mellitus type 2 (10%), cardiac arrhythmia/atrial fibrillation (5%), autoimmune disorders (20%), allergy (11%), malignancy (3%), headache (15%) and mental disorders (20%). Patients with narcolepsy showed double the excess prevalence in mental disorders (OR 2.15, p < 0.05), and dyslipidaemia (OR 2.22, p < 0.05). The presence of autoimmune disorders and allergy showed a mild increase in the narcolepsy group (OR 1.46, resp. 1.63). Hashimoto thyroiditis (HT) was the most frequent autoimmune disorder. ConclusionsNarcolepsy is a rare disorder in Slovakia. From the phenotype, genetic characteristics and comorbidities the disorder does not vary from other European countries.