Regional effect of population-based programs promoting salt reduction and potassium intake in Hokkaido: a post hoc analysis of the PoSPIP.

Abstract

The Population-based Sodium/Potassium Improvement Program is a nonrandomized population-based intervention implemented by the Japanese Society of Hypertension across multiple municipalities and workplaces in Japan. This post hoc regional analysis focused on two municipalities in Hokkaido-namely, Higashikagura, which received standard support, and Mashike, which received intensive support consisting of on-site urinary sodium-to-potassium (Na/K) ratio measurement, immediate feedback, repeated health guidance, and food-environment improvement. A total of 431 participants who underwent annual health checkups in 2021 and 2022 and had urinary Na/K ratio data at both time points (standard support group, n = 218; intensive support group, n = 213) were included. One-year changes in the urinary Na/K ratio, estimated salt and potassium intakes, blood pressure (BP), and other clinical measures were compared between the groups using multivariable linear regression. The proportion of participants achieving urinary Na/K ratio targets increased in the intensive support group. A significant group-by-time interaction was observed for the <2 threshold (OR 2.62, 95% CI: 1.25-5.50), but not for the <4 threshold. After adjustment for covariates, estimated salt intake decreased more in the intensive support group than in the standard support group (adjusted group difference: -0.53 g/day, 95% confidence interval: -0.95 to -0.12). Changes in the urinary Na/K ratio, estimated potassium intake, and systolic and diastolic BP did not significantly differ between the groups. Intensive support incorporating urinary Na/K ratio measurement, immediate feedback, and repeated multidisciplinary guidance may promote salt reduction in local community settings.