Impact of Salt Reduction on Medical Expenditure for Hypertension in Japan: National and Subnational Simulation Models

Objective: Excessive salt intake affects blood pressure. Thus, monitoring of salt intake is vital in the aging population. In this study, we examined the impact of salt intake reduction on medical expenditure for hypertension in Japan. Methods: System dynamics models for Japan and its 47 prefectures were developed using sub-models of salt intake, population, hypertension, and treatment costs. Co-flows of foods with high and low salt content and people with high and low salt intakes were built to calculate the daily salt intake. Aging chains of 10-year age groups from 40 to 79 years were built by sex for the population and people with hypertension (PwH). The outpatient treatment costs for hypertension were also calculated. The model parameters were calibrated using national statistics from 2012 to 2023, and prefectural models were developed to address the gaps in the national data for 2012. The simulated changes were compared across scenarios. Results: In the base run from 2012 to 2040, a reduction of 46.3% of high-salt foods and 33.1% of people with high salt intake would make a 13.9% reduction in daily salt intake from 10.1 g/day to 8.7 g/day. When salt intake is reduced to 6.9 g/day in 2040, PwH and treatment costs decrease by 2.3% and 2.0% in men and by 8.8% and 8.3% in women, respectively. The prefectural models exhibited the simulated changes. Conclusions: Our models suggest that reducing salt intake will lead to a decrease in the number of PwH and outpatient treatment costs by 2040.