Objectives Social capital consists of two subordinate concepts; first one is structural formal, structural informal, or cognitive and second one is bonding or bridging. This study was designed to develop a social capital scale using samples from a national longitudinal survey and evaluate the validity and test-retest reliability of the scale.Methods Data were collected from a nationwide panel survey, the "Longitudinal Survey of Middle-aged and Elderly Persons." Individuals aged 50-59 years living in Japan were selected by stratified random sampling in the first wave conducted in 2005. The first (n=34,240) and second (n=32,285) sets of data were used for Phase 1, and the sixth (n=26,220) and seventh (n=25,321) sets of data were used for Phase 2. In regard to first subordinate concept, the occurrence of six selected social activities with "neighborhood association" and "NPOs, or Public Interest Corporations" were calculated as the structural formal index, and the occurrence of six selected social activities with "families or friends" and "colleagues" were calculated as the structural informal index. Moreover, satisfaction with social activities (community activities, support for the elderly, and others) was used as the cognitive index. In regard to second subordinate concept, the bonding index was calculated using "families or friends," "colleagues," and "neighborhood association;" the bridging index was calculated using "NPOs or Public Interest Corporations." The diagnoses of heart disease, stroke, and cancer (yes=1, no=0) and self-rated health (1 item, 6-point scale) were used as variables for determining validity.Results We categorized social capital indices into subordinate concepts based on the construct of social capital defined by professional agreement to assess content validity. The results showed that this survey questionnaire was constructed using items that assessed all the subordinate concepts. Hierarchical Linear Modeling examined the relationship between social capital and health as assessed by diagnoses of physical disease and self-rated health to examine convergent validity, which indicated that all social capital indices had significant positive effects on self-rated health at an individual or group level. However, the diagnosis of a stroke was negatively influenced by cognitive and formal social capital indices at a group level, whereas heart disease and cancer were not significantly affected. Multilevel correlation analyses of Phase 1 (the first and second) and Phase 2 (sixth and seventh) were conducted to assess test-retest reliability, which indicated correlation coefficients of 0.392 to 0.999.Conclusion The findings of this study indicated the content validity of the scale that was developed from the national longitudinal survey. Moreover, results of Hierarchical Linear Modeling confirmed the partial convergent validity of the scale. Furthermore, multilevel correlation analyses demonstrated the adequate test-retest reliability of the scale at the group level.
Keywords: development of scale; longitudinal survey of middle-aged and elderly persons; multilevel analysis; reliability; social capital; validity.