Hypersomnia causes significant socioeconomic burden, but there is insufficient information about the time course and the effect on the partner. The aim of this study was to estimate the factual direct and productivity costs of hypersomnia in a controlled study including all national patients and their partners. Using records from the Danish National Patient Registry (1997-2009), we identified all patients with a diagnosis of hypersomnia and compared these patients and their partners with randomly chosen controls matched for age, gender, geographic area and marital status. Direct and productivity costs, including frequencies of primary and sector contacts and procedures, medication, labour supply and social transfer payments were extracted from the national databases. A total of 2,855 national patients was compared to 11,382 controls. About 70 % of patients and controls were married or cohabiting. Patients with hypersomnia had significantly higher rates of health-related contact, medication use and socioeconomic cost. Furthermore, they had slightly lower employment rates, and those in employment had a lower income level than control subjects. The annual mean excess health-related cost including social transfers was <euro>3,498 for patients with hypersomnia and <euro>3,851 for their partners. The social and health-related consequences could be identified up to 11 years before the first diagnosis among both the patients and their partners and became more pronounced as the disease advanced. The health effects were present in all age groups and in both genders. On the basis of this retrospective controlled study in the Danish population, symptoms and findings of hypersomnia are associated with major socioeconomic consequences for patients, their partners and society.