Studies using real-world data are recently increasing worldwide. Various types of real-world data are available in Japan. Administrative claims databases include the National Database (NDB) and other types of databases including several commercially available databases. This article describes the DeSC database, newly constructed by DeSC Healthcare Co., Ltd. in 2020. One of the features of the DeSC database is that it includes data from the National Health Insurance, Health Insurance, and Advanced Elderly Medical Service System. In the present article, we referred to our previous study on population representativeness of the DeSC database and explained its overview. Estimated prevalence of some diseases were described for each type of insurance. Furthermore, we discussed the use of the DeSC database for clinical epidemiology and pharmacoepidemiology research.

The Tokushukai Group is one of the largest hospital groups in Japan. By connecting all the hospitals via a network, the group has been able to achieve centralized management of clinical information. The Tokushukai Group has been utilizing the data in various ways, such as participation in clinical trials, development of anticancer drug protocol systems, participation in BioBank Japan, and provision of data to MID‒NET®. These days, the Tokushukai Group has started to provide the data, named as the “Tokushukai Medical Database (TMD)”, to academia and industries for research purposes. The TMD mainly consists of inpatient and outpatient administrative claims data, Diagnosis Procedure Combination (DPC) data, electronic health records including blood test results and vital signs, and hospital-based cancer registry information. The strengths of the TMD include the availability of blood test results and vital signs in an standardized format, and the possibility to go back to each patient's electronic medical record from their claims data and DPC data, with the permission of headquarters and the ethics committee in the Tokushukai group. By taking advantage of these strengths, there have been increasing number of studies in the TMD, such as research on acute kidney injury defined as blood test results, hyperkalemia in dialysis patients, and validation study on rheumatoid arthritis. The issues newly raised during the utilization of data (e.g., echocardiography data not standardized) are expected to be resolved with the update of the network system for a wider range of research topics in the future.

Kobe City has developed a new “Healthcare Data Integration System” that links and anonymizes health care data such as medical and nursing care claims data and medical checkup data, and started its operationin November 2020. Kobe City aims to improve healthcare services through the promotion of data-driven evidence-based policymaking using the same system. This system contains consolidated data on an individual basis for about 600,000 citizens, such as medical claims data, nursing care claims data, health checkup data, nursing care certification records, and immunization data. These consolidated data can be used free of charge for research purposes, but only by academic institutions. The use of the data must be approved by the Institutional Review Board of Kobe City. The minimum necessary data set is created according to the content of the research and is anonymized so that individuals cannot be identified. Kobe City uses the data stored in the “Healthcare Data Integration System” for two purposes： first, to understand and keep track of the health status and health issues of citizens, and second, to accelerate the use of data for research purposes. When the research of high public value is conducted based on Kobe City's data, new findings from the results can be reflected in health services by the government. Byaccelerating the use of the “Healthcare Data Integration System”, Kobe City is expecting to further improve health services for all citizens.

The beginning of EHR (Electronic Health Record) can be traced back to the development of the Medical Markup Language (MML) from 1995 to 2000. In 2001, EHR with MML as a database structure was developed and expanded to Kumamoto, Miyazaki, Tokyo, and Kyoto (Dolphin Project). After that, the need for medical information management at the national level was recognized, and the need for secondary use of medical information was also recognized, and in 2015, the national level version of the EHR, the “Millennial Medical Record Project” began. The number of connected medical institutions reached 106 in the four years up to FY2018. In December 2019, the Life Data Initiative, a general incorporated association, became the first certified company under the Next Generation Medical Infrastructure Law, and is operating with the aim of achieving independent profitability, including the EHR department, which does not depend on subsidies.

Real World Data (RWD) has various types of data sources, but each source has a different format and terminology code, which makes analysis process cumbersome and repetitive. The OMOP Common Data Model (CDM) is an open standard for analysis of RWD on a global scale, and the OHDSI community is responsible for its maintenance and development. What sets the OMOP CDM apart from other data standards is the way in which it has created a structure for integrating and handling terminology globally, and the way in which analysis is conducted without exposing individual patient information outside. Such features facilitate international collaboration. The method of not releasing patient data outside is expected to be widely utilized in future because it is highly compatible with Japan's pseudonymously processed information (PPI) based on the personal information protection act, in which PPI data cannot be provided to any third party but the purpose of use can be easily changed. There are many advantages not only for international collaboration, but also for domestic collaboration or in-house use. Epidemiologists and data scientists will be able to handle data in the same model they are accustomed to both domestically and internationally. That will be of great benefit to students, personnel, and their organizations especially when they study abroad, return home, or transfer internationally. Globally, collaborators from more than 70 countries are working on this project. Data on more than 800 million people after eliminating estimated duplicates, or 10％ of the world's population, has been converted to the OMOP CDM. More than 250 related published articles have been registered with PubMed. On the other hand in Japan, there are many issues to be solved, such as support system and terminology mapping. To catch up with international levels, strong cooperation from a wide range of fields is needed.