Abstract
JMDC, Inc. (JMDC) has created a database, using data collected from health insurance societies in Japan, consisting of ledgers of insureds, claims (for hospitalization, outpatient treatment, drug preparation, and dental treatment), and health checkup results. The earliest data are from the claims in January 2005, except dental claims from December 2009 and health checkup results from April 2008. Currently (the end of June 2020), the number of insureds included is approximately 9.8 million. This database is unique for Japan and has the following characteristics: (a) the basic population can be ascertained; (b) standardization is carried out using a dictionary; and (c) anonymized individual IDs can be followed on the basis of a time-series over various periods, with the earliest starting date being January 2005. However, it has certain limitations, in that the disease status and test results cannot be ascertained, and there is insufficient access to data for elderly people.