Understanding Costs and Health Utilities in Relation to Symptom Burden in a Large European Survey of Patients With Central Disorders of Hypersomnolence

OBJECTIVES: Central disorders of hypersomnolence (CDH) are rare disorders characterized by excessive daytime sleepiness, cataplexy and/or excessive need for sleep. Little evidence is available on health and economic consequences of CDH related to disease severity. We estimated resource utilization, costs and health utilities relative to symptom severity in CDH across six European countries.

METHODS: Patients with narcolepsy type 1 (NT1), type 2 (NT2) or idiopathic hypersomnia (IH) were invited to participate in a cross-sectional survey through specialist clinics, patient associations and disease registries in Sweden, France, Italy, Germany, United Kingdom and Switzerland. Data were collected on clinical symptoms using validated scales (ESS, NSS-CT, IHSS), resource utilization and health-related quality of life (EQ-5D). Disease severity stages were developed by constructing linear combination of (standardized) total costs and health utilities using principal component analysis. Stepwise linear models were built including measures of symptom severity as explanatory variables. Finally, patients were divided into quintiles based on the predicted values from this model, representing five states of increasing disease severity.

RESULTS: 1818 patients completed online (81%) or postal (19%) surveys. Mean age was 37.5 years (range 18-93), 71% were female. Resource utilization was dominated by work productivity loss. Costs and utilities in pooled study population were explained by NSS-CT, self-reported disease severity, daytime sleepiness, disturbed nighttime sleep, nap time and limitations in daily activities from fatigue and subjective cognitive impairment. Total costs ranged from €11,041 per year in the mildest group to €25,402 in the most severe group, while utilities ranged from 0.936 to 0.585.

CONCLUSIONS: This was the first study to understand the link between symptom burden, costs and utilities, in a large European survey of narcolepsy and IH patients treated in routine care. The study will support modelling of costs and utilities depending on the severity of symptoms and treatment in CDH.