Nationwide Comprehensive Epidemiological Study of Rare Diseases in Japan Using a Health Insurance Claims Database

BackgroundMore than 7,000 diseases constitute what are called rare diseases, and they mostly have no specific treatment. Disease profiles, such as prevalence and natural history, among the population of a specific country are essential in determining for which disease to research and develop drugs. In Japan, disease profiles of fewer than 2,000 rare diseases, called Nanbyo, have been investigated. However, non-Nanbyo rare diseases remain largely uninvestigated. Accordingly, we reveal the prevalence and natural history of rare diseases among the Japanese population, using the National Database of Health Insurance Claims and Specific Health Checkups of Japan, which covered 99.9% of public health insurance claims from hospitals and 97.9% from clinics as of May 2015. Then, we compared them with the data reported in Orphanet. This cross-disease study is the first to analyze rare-disease epidemiology in Japan with high accuracy, disease coverage, and granularity.ResultsWe were provided with the number of patients of approximately 4,500 rare diseases by sex and age for 10 years with the permission of the Ministry of Health, Labour and Welfare. About 3,000 diseases have equivalent terms in Orphanet and other medical databases. The data show that even if the Nanbyo systems do not cover a rare disease, its patients survive in many cases. Moreover, regarding natural history, genetic diseases tend to be diagnosed later in Japan than they are in the West. The data collected for this research work are available in the supplement and the website of NanbyoData.ConclusionsOur research work revealed the basic epidemiology and the natural history of Japanese patients with rare diseases using a health insurance claims database. The results imply that the coverage of the present Nanbyo systems is inadequate for rare diseases. Therefore, fundamental reform might be needed to reduce unfairness between rare diseases. Moreover, most diseases in Japan follow a tendency similar to those reported in Orphanet. However, some diseases are detected later, partly because fewer clinical genetic tests are available in Japan than there are in the West. Finally, we hope that our data and analysis accelerate drug discovery for rare diseases in Japan.