Importance: Type 2 diabetes and hypertension are obesity-related, noncommunicable diseases becoming increasingly common worldwide. In 2008, Japan launched a nationwide universal health checkup program, Specific Health Checkup (SHC), for the primary prevention of obesity-related diseases, but its effectiveness has been understudied.
Objective: To investigate the association of the SHC program with incident diabetes and hypertension, using a target trial emulation framework.
Design, setting, and participants: This retrospective cohort study used data from a longitudinal health care database involving both checkup history and medical encounter records in Japan. Individuals aged 40 to 74 years, without diabetes or hypertension, and without a prior checkup history, were eligible. Individuals were repeatedly assessed for eligibility from April 1, 2008, to March 31, 2020, to assemble sequential cohorts of 78 620 SHC participants and 214 554 nonparticipants. Statistical analysis was conducted from June 8 to December 30, 2023.
Main outcomes and measures: The composite risk of incident type 2 diabetes or hypertension over a period of up to 10 years, defined as the combination of a newly documented diagnosis and use of relevant medications. A propensity score-weighted survival analysis was conducted to adjust for baseline variables. A series of sensitivity analyses and a negative outcome control analysis were conducted using depression as a benchmark.
Results: Sequential cohorts consisted of 78 620 SHC participants (median age, 46 years [IQR, 41-53 years]; 62.7% women) and 214 554 nonparticipants (median age, 49 years [IQR, 44-55 years]; 82.0% women) from 153 084 unique persons, each of whom entered the study cohort a mean (SD) of 1.9 (1.5) times. Within a median follow-up of 4.2 years (IQR, 2.7-6.3 years), the primary end point occurred among 11.2% of all individuals (10.6% of the SHC participants and 11.4% of the nonparticipants), with a lower hazard ratio (HR) among the SHC recipients (HR, 0.90; 95% CI, 0.89-0.92); the difference in cumulative incidence at 10 years was -1.6% (95% CI, -1.8% to -1.3%). The sensitivity analyses showed similar results. The negative control analysis suggested the potential for residual confounding (HR, 1.05; 95% CI, 1.02-1.07); the bias-calibrated HR was 0.86 (95% CI, 0.84-0.89) for the primary outcome.
Conclusions and relevance: In this cohort study, within a median of 4.2 years of follow-up, SHC recipients had a 9.8% lower risk of incident diabetes and hypertension (13.8% in the bias-calibrated analysis). The cost-effectiveness of the SHC and its transportability to other regions are unclear, requiring future investigations.