Effectiveness of Specific Health Check-ups in Japan for the primary prevention of obesity-related diseases: a protocol for a target trial emulation

INTRODUCTION: Concerns about public health threats have shifted towards obesity-related, non-communicable diseases in both developed and developing countries. Since 2008, Japan has adopted a nationwide universal screening programme called Specific Health check-ups (SHC) for the primary prevention of obesity-related, non-communicable diseases, namely, diabetes, hypertension and hyperlipidaemia. The effectiveness of SHC has not been systemically evaluated to date. METHODS AND ANALYSIS: We will use the employment-based health insurance database, which includes both records of receipt versus non-receipt of SHC and healthcare claims. The study design adopts the target trial emulation framework to minimise the bias inherent to the observational study (eg, time-related bias and its consequences). The key components of trial emulation—eligibility criteria, treatment strategy, assignment procedure, follow-up period, outcome, causal contrast of interest and analysis plan—are detailed, along with the ideal target trial protocol. Briefly, we will conduct the nested-trial emulation approach that allows multiple trial entries. Persons aged 40–74 years will be eligible if they do not have a documented diagnosis of hypertension and diabetes and a history of receiving SHC at baseline. Participants will be classified according to the receipt or non-receipt of SHC service and followed for a maximum of 10 years until the withdrawal from the insurance plan, the outcome occurrence or the administrative censoring (the end of the available data, expected to be March 2022), whichever comes first. The 10-year incidence of diabetes/hypertension will be compared between SHC recipients and non-recipients using pooled logistic regression with adjustments for baseline confounders. Five sensitivity analyses are employed, including per-protocol analysis, changing eligibility criteria and negative outcome control analysis. ETHICS AND DISSEMINATION: This protocol obtained the approval from Kyoto University Graduate School and Faculty of Medicine, Ethics Committee (R2448). The findings will be disseminated to academic conferences, and published in a peer-reviewed journal.