Impact of opening new train stations on regional health expenditures per capita for middle-aged adults: A natural experiment of the Osaka-Higashi Line

The Japanese government has promoted the Compact Plus Network, which encourages people to live near train stations for health benefits. This study aimed to elucidate the impact of the opening of new train stations on the regional health expenditure per capita for medically treated middle-aged adults. The analysis provides insight into the characteristics of the stations that reduce the expenditure. This study employed a natural experiment design, utilizing the time difference in the opening period of the Osaka-Higashi Line. The Osaka-Higashi Line has a southern section that opened in 2008 and a northern section that opened in 2019. This study designated the four station areas surrounding the stations in the northern section, where a new station opened in 2019, as the exposure group. This analysis was conducted at two levels: the railway-line and individual station levels. The area surrounding the stations in the southern section was designated the covariate group. Our statistical analysis used the Causal-Impact algorithm on the medical dataset REZULT. This study analyzed 96-months before and after the opening of new stations. Our analysis sample has no significant changes in demographic characteristics before or after the stations’ opening. This study clarified that only the exposure groups (Shigino) reduced the cumulative health expenditure per capita by JPY 62,500.62 [95 %CI: −141218.67, 21306.54] over four years. However, the expenditure did not decrease in the exposure groups of the north section at the railway-line level, and JR-Awaji, Shirokitakōendōri, and JR-Noe stations at the individual station level. New-station openings did not yield a significant overall line-level reduction in RHE over four years, but we observed station-level heterogeneity, with Shigino showing an estimated cumulative reduction ( p = 0.06). Pre-opening higher RHE and stronger inter-network connectivity emerge as plausible moderators, suggesting targeted, station-screening approaches for health-informed rail planning. • Impact of the opening of new train stations on health expenditure per capita. • Natural experiment using the case of the Osaka-Higashi Line. • The expenditures are reduced JPY 62,500.62 over four years in Shigino Station. • The expenditures did not decrease in the new line as a whole with all stations. • Expenditure decreased at the station, which was higher before its opening.