In recent years, there has been an increase in the number of database studies within the healthcare sector. This upsurge can be attributed to various factors such as the revision of related laws and regulations, widespread adoption of data sharing practices, proliferation of available data sources, digitization and standardization of historically collected data, advancements in digital technology, and the steady promotion of evidence-based medicine and policymaking. In Japan, database studies encompass a broad spectrum of areas, including research based on administrative-claims databases, disease registries, cohort studies, and electronic medical records. This review focuses on the current status and trends in database studies in Japan. An analysis of data of five years (2018–2022) retrieved from PubMed, provided further evidence for the growing prominence of database research in Japan. This surge is likely linked to the expansion of the available databases. Database studies can yield new insights into areas such as patient assessment and the decision-making processes in medical care, health services, and policy formulation. There is a growing expectation that database studies will continue to provide reliable evidence in the future.

In this article, we emphasize practical approaches to policy research using medical and long-term care insurance claims data in Japan. We aim to highlight the challenges faced when using claims data for policy-making and to clarify areas of concern when advancing such research. Specifically, we use a policy research initiative related to the promotion of coordination between home medical care and long-term care as a case study. Within this project, we discuss the challenges faced in developing effective evaluation metrics using claims data.

In our selected case study, we examined whether data on four key areas necessitating coordination between home medical care and long-term care in the daily lives of home care patients can be extracted from the linked medical and long-term care insurance claims database (Nara Prefecture KDB). These areas include daily medical and care support, admission and discharge support, emergency response, and end-of-life care. This examination includes defining these metrics on the claims. Recognizing that local governments primarily use the ‘Visualization System for Community-Based Integrated Care’ to gain quantitative insights into their initiatives, we also reviewed the precautions necessary when extracting data from this system. Furthermore, we conducted interviews to assess the initiatives of Municipality A, considered a leading authority on the promotion of coordination between home medical care and long-term care within the target prefecture.

The study results suggest the need to initially define metrics on the claims for most of the four key areas. Although the numbers of claims for home medical care retrievable from the Visualization System are based on extractions from the National Database of Health Insurance Claims and Specific Health Checkups of Japan, these definitions are not explicitly disclosed. Given that the values extracted from claims can vary based on the definitions of medical procedure codes, caution is necessary when municipalities individually extract and employ data from their available KDBs. Particularly when comparing between municipalities, there is a risk that the use of different definitions might result in the retrieval of unrelated data, resulting in invalid comparisons. It is necessary to ensure that the definitions of data extracted from the claims within the Visualization System are verifiable across municipalities. As the emphasis on using claims data in government administration increases, potentially gaining more recognition as evidence for shaping policies, the importance of aligning the promotion of claims use by the administration with policy research is likely to grow.

The Ministry of Health, Labour and Welfare has established a database that accumulates medical information obtained from the exclusive medical certificates provided by physicians for applying for medical expense subsidies for children with chronic diseases. These data are available for secondary use, including disease research.

The large database covers 788 diseases, including almost all chronic pediatric diseases and many rare diseases. Its unique design allows the estimation of the same cases by probabilistic record linkage within the database, enabling its use as longitudinal data.

From October 2023, it will be possible to assign new anonymized personal identification information (ID5) based on the historical hash value of the individual unit-insured person number.

Linkage with other national databases, such as the National Database of Designated Incurable Diseases and health insurance claims data, which have the same mechanism, is expected. Access to chronic pediatric disease data can surely enable further research on such diseases.

In addition to having critical organs for eating, swallowing, and breathing, the head and neck region play vital roles in daily life, supporting vision, hearing, balance, smell, taste, and communication. Multimodal treatments, including surgery, radiation therapy, and pharmacotherapy have been developed to treat head and neck cancers and maintain these functions. With approximately 48,000 cases reported annually, head and neck cancers are relatively rare in Japan. Moreover, head and neck cancers can originate in various regions, including the oral cavity, nasal cavity, paranasal sinuses, nasopharynx, oropharynx, hypopharynx, larynx, thyroid, and salivary glands. The low incidence and diverse origins make it challenging to conduct randomized, interventional clinical trials. Therefore, we aimed to collect as many cases as possible by renewing the existing National Clinical Database operated by the Japan Society for Head and Neck Cancer (JSHNC) to construct a registry for the utilization of big data.

With the objective of updating the annual epidemiological data and state of medical practice for head and neck cancer in Japan, the JSHNC has been collecting and registering national cases of malignant tumors in the head and neck region using the National Database for Head and Neck Cancer (INDICE) of UMIN. The number of registered cases has increased dramatically since registration has become mandatory for all training facilities for board-certified head and neck surgeons. To address the increasing workload of committee members, we outsourced the data center operations to the Wakayama Medical University Hospital Clinical Research Center. It has now become possible to accurately manage clinical data on more than half of the patients with head and neck cancer in Japan. In addition, we developed a new software to enable the automatic upload and registration of baseline data of hospital-based cancer registries to the INDICE to reduce the data entry burden on institutions.

We developed a web-based Case Report Form for each project using the UMIN INDICE. The first project was a retrospective observational study conducted on patients with HPV-related oropharyngeal cancer, and 746 cases were identified from 34 institutions. Based on the accumulated data, we generated the most suitable treatment plan and optimal total dosage of CDDP in concurrent chemoradiotherapy according to the cancer stage for patients with p16-positive (HPV-related) oropharyngeal squamous cell carcinoma.

Human T-cell leukemia virus type 1 (HTLV-1)-associated myelopathy (HAM) is a severe refractory disease characterized by progressive paraparesis due to chronic inflammation of the spinal cord for which only a few effective treatments exist. Given its low prevalence in developed countries outside of Japan, only limited data on biomarkers and treatment strategies are available internationally. Consequently, there is no globally recognized treatment for HAM, resulting in suboptimal clinical care. In the case of rare diseases, such as HAM, conducting large-scale studies to continuously collect clinical data has proven challenging. Recognizing the potential value of a patient registry in gathering information from a diverse patient population, we established the nationwide registration system“HAM-net” in 2012, which has proven to be an invaluable tool for advancing epidemiological research.

The Japan Environment and Children's Study (JECS) is a large-scale birth cohort study conducted since 2011. This study aimed to determine how environmental factors, particularly exposure to chemicals during fetal and childhood periods, affect children's health and development. In recent years, increasing health problems among children have resulted in growing concern about the impact of the environment, especially regarding the increasing amounts of chemical substances in children's surroundings. As children are particularly vulnerable to environmental impacts during their fetal and childhood periods, the implementation of environmental policies to protect their health is considered an urgent issue. Several cohort studies focusing on children have been conducted worldwide. Approximately 100,000 pregnant women, 50,000 fathers of children, and 100,000 newborns were registered in the JECS between 2011 and 2014. Currently, the JECS plans to continue collecting data until the children become 40 years of age. In addition to data from questionnaires, medical records, medical examinations, assessments of neuropsychiatric development, and environmental measurements, various biological samples including blood, urine, hair, breast milk, and baby teeth were collected. This paper outlines the plan for JECS, with a particular focus on data collection and management and presents some of the research and its findings.

With the introduction of Japan's specific health examination (hereafter referred to as ‘health checkup’), the standardization of blood biochemistry tests at each facility was promoted.

The Association for Preventive Medicine of Japan (hereinafter referred to as the ‘Association’) conducts health examinations throughout Japan as an occupational health registration organization and has received Privacy Mark certification. This time, we analyzed AST, ALT, γ-GT, total cholesterol (T-CHO), triglyceride (TG), HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C), Blood sugar (GLU), hemoglobin A1c (HbA1c, NGSP (international standard) value), and creatinine (CRE) and uric acid (UA), which are often performed at the same time as a legal medical examination, and BMI (Body Mass Index) as an index of the overall condition of the body from 2008 to2017.

First, we calculated individual variation for the five years from 2008 to 2012 as one segment. The calculation results were verified by comparing them with individual variation ranges calculated for five groups, starting from 2009 to 2013.

As a result, there was no difference between each group and the reference year (2008 study start group) (p>0.05), so the initial calculated value was determined as a representative individual variation. This value was obtained from healthy subjects, and its application is limited to individuals showing test values ​​within the reference range. It is speculated that it can be applied to early improvement guidance for health conditions, such as when the numerical value rises beyond the individual variation.

In the future, it is expected that it can be used as an indicator for changes in health checkup values for each individual.

Health economic evaluations are comparative analyses of alternative courses of action in terms of their costs and consequences. The Consolidated Health Economic Evaluation Reporting Standards (CHEERS) statement, published in 2013, was created to ensure health economic evaluations are identifiable, interpretable, and useful for decision making. It was intended as guidance to help authors report accurately which health interventions were being compared and in what context, how the evaluation was undertaken, what the findings were, and other details that may aid readers and reviewers in interpretation and use of the study. The new CHEERS 2022 statement replaces the previous CHEERS reporting guidance. It reflects the need for guidance that can be more easily applied to all types of health economic evaluation, new methods and developments in the field, and the increased role of stakeholder involvement including patients and the public. It is also broadly applicable to any form of intervention intended to improve the health of individuals or the population, whether simple or complex, and without regard to context (such as healthcare, public health, education, and social care). This Explanation and Elaboration Report presents the new CHEERS 2022 28-item checklist with recommendations and explanation and examples for each item. The CHEERS 2022 statement is primarily intended for researchers reporting economic evaluations for peer-reviewed journals and the peer reviewers and editors assessing them for publication. Nevertheless, we anticipate familiarity with reporting requirements will be useful for analysts when planning studies. It may also be useful for health technology assessment bodies seeking guidance on reporting, given that there is an increasing emphasis on transparency in decision making.