Does district-level social capital have a beneficial effect on self-rated health? a study in a suburban city in the greater tokyo area

Objective: The Greater Tokyo area has seen the development of many suburban commuter cities which has a rapidly aging population and high population fluidity now. Many studies have reported the relationship between Social Capital (SC) and self-rated health (SRH) in typical cities, but there has been no previous study of this relationship in such a unique area. This study examined the relationship between district-level SC and SRH among the general population of one suburban city. Methods: A cross-sectional mail-in survey was conducted in 2009. The participants were 4,123 randomly selected people, aged 20+, living in 72 districts in Kashiwa city, Chiba prefecture. We measured demographics, socioeconomic status, SRH, and four SC indicators: trust for the neighbors (cognitive/horizontal SC), institutional trust for the national social security system (cognitive/vertical SC), participation in hobby, sports, or recreation groups (structural/horizontal SC), and participation in neighborhood associations (structural/vertical SC). District-level SC was calculated by aggregating the individual scores of each SC indicator within each district. Results: The analysis included 1,716 questionnaires. A multilevel analysis showed that district-level institutional mistrust was associated with poor SRH. Interestingly, district-level mistrust for the neighbors was inversely associated with poor SRH. Conclusions: People in suburban areas may feel psychological stress in close relationships or mutual cooperation among neighbors. Therefore, intervention to increase trust among neighbors might negatively affect residents' health, while intervention to build institutional trust would be effective. Our finding provides interesting evidences to understand the direction of community health promotion strategies for the aging nations of the future.