Effects of salt reduction project implemented by local governments in Nakatsugawa City: study protocol and participant characteristics for observational study

Abstract Background The salt intake among the Japanese population exceeds recommended levels, contributing to adverse health outcomes. The age-adjusted mortality rate due to cerebrovascular disease in Nakatsugawa City, a mountain town in Gifu Prefecture, Japan, is higher than the national average. The prevalence of hypertension, a risk factor for cerebrovascular disease, is also higher than the national average. A leading factor contributing to these health challenges is the high salt intake among Nakatsugawa residents. Consequently, Nakatsugawa City initiated a 3-year salt reduction project modeled on the Aki area as part of its health promotion endeavors, targeting all residents, including adults and elementary school and junior high school students. We present a protocol for our observational study aimed to evaluate the efficacy and cost-effectiveness of this comprehensive salt reduction initiative. Methods This salt reduction project will target approximately 2,000 residents of the Aki district, and this study will invite a total of 93 households with elementary or junior high school students in the Aki district for participation. Intervention strategies for this project include classes on the theme of salt reduction and salt reduction in school lunches at elementary and junior high schools, lectures on salt reduction in the community, regular communications on the theme of salt reduction, distribution of low-salt seasonings and blood pressure monitors to households, and evaluation and feedback of individual salt intake. Discussion Overall, 69 households (74.2%) and 253 individuals (61.4%) participated in the project's evaluation study. Analysis of urinary salt content measurements revealed that the estimated daily salt intake across various age groups exceeded the standard daily intake specified in the 2020 Dietary Intake Standards for Japanese by the Ministry of Health, Labor, and Welfare. These findings underscore Nakatsugawa City's suitability as an implementation area for a salt reduction project. The project's first year cost was approximately $45,300, aligning with the project's $150,000 scheduled total budget for the initial year within the 3-year project duration. The first year of the intervention is progressing as planned, encompassing both effective implementation and adherence to budgetary allocations. The findings could provide valuable insights into the impact of this salt reduction initiative on health outcomes. Trial registration: This study complies with the "Ethical Guidelines for Medical Research Involving Human Subjects" December 22, 2014 (partially amended on February 28, 2017): Ministry of Education, Culture, Sports, Science and Technology and Ministry of Health, Labour and Welfare and was approved by the Bioethics Review Committee of the Nagoya University Graduate School of Medicine (2020/5/29, approval number 2020-0040).