Development of the health literacy on social determinants of health questionnaire in Japanese adults

BACKGROUND Health inequities are increasing worldwide, with mounting evidence showing that the greatest cause of which are social determinants of health. To reduce inequities, a lot of citizens need to be able to access, understand, appraise, and apply information on the social determinants; that is, they need to improve health literacy on social determinants of health. However, only a limited number of scales focus on these considerations; hence, we developed the Health Literacy on Social Determinants of Health Questionnaire (HL-SDHQ) and examined its psychometric properties. METHODS We extracted domains of the social determinants of health from "the solid facts" and related articles, operationalizing the following ten domains: "the social gradient," "early life," "social exclusion," "work," "unemployment," "social support," "social capital," "addiction," "food," and "transport," Next, we developed the scale items in the ten extracted domains based on the literature and included four aspects of health literacy (ability to access, understand, appraise, and apply social determinants of health-related information) in the items. We also evaluated the ease of response and content validity. The self-administered questionnaire consisted of 33 items. The reliability and construct validity were verified among 831 Japanese adults in an internet survey. RESULTS The scale items had high reliability with a Cronbach's alpha of 0.92, and also adequate results were obtained for the internal consistency of the information-processing dimensions (Cronbach's alpha values were 0.82, 0.91, 0.84, and 0.92 for accessing, understanding, appraising, and applying, respectively). The goodness of fit by confirmatory factor analysis based on the four dimensions was an acceptable value (comparative fit index = 0.901; root mean square error of approximation = 0.058). Furthermore, the bivariate relationship between HL-SDHQ and the frequency of participation in citizen's activities was similar to the theoretical results. CONCLUSIONS HL-SDHQ clarifies the relationship between the ten domains of the social determinants of health and health in each domain and is able to measure whether it is possible to access, understand, appraise, and apply related information. The reliability and validity of the scale were adequate.