From Insurance Records to Epidemiology: Provenance and Processing of Japanese Claims Data

Administrative claims data have become central resources for epidemiology and health services research in Japan. These datasets provide large sample sizes, longitudinal coverage, and standardized coding, and are increasingly treated as “ready-made” sources for descriptive, causal, and predictive research. However, they are by-products of an insurance and reimbursement system, not purpose-built research registries. What is captured, and what is missing, is determined by institutional arrangements, fee schedules, and clinical workflows. Without understanding how these data are generated and processed, investigators risk misinterpreting variables, underestimating bias, and over-trusting sophisticated analyses.

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