Mixed methods investigation of the meanings of one inequality indicator (the Japanese Small Area Deprivation Index) for researching social inequalities in health in the Soma Region of Fukushima, Japan

Abstract

In the process of researching social inequalities in health, certain indicators (e.g. socioeconomic position; small area deprivation) are now widely used across many countries. However, there has been limited research on how these indicators may have different meanings in different contexts, to both researchers and to lay actors, and how potential differences in meaning may impact the representation of social inequalities in health in research findings. Drawing on a critical realist perspective, this thesis explores the extent to which the use of one indicator —the Japanese Small Area Deprivation Index (JSADI)— is meaningful to different stakeholders in the assessment of social inequalities in health in the Soma Region of Fukushima, Japan following the 3.11 triple disaster. This includes exploration of the meaning of the JSADI to researchers who use it in attempts to measure social inequalities in health in Japan; the extent to which its use produces meaningful statistical results on social inequalities in health in the Soma Region; and the ways in which the findings produced through its use are meaningful to lay actors in the Soma Region. A mixed methods approach is taken. Multi-level models are constructed to quantitatively determine whether social inequalities in one health outcome (diabetes) are evident in the Soma Region in relation to small area deprivation as defined by the JSADI, drawing on public health check data (a cohort of 6,093 individuals, 2008 to 2014). Qualitative interviews are undertaken with 16 researchers and 47 lay actors from the researched communities, and thematically analyzed. The thesis finds that use of the JSADI presents diverging lines of meaning to each stakeholder group. Researchers experienced use of the JSADI as meaningful and necessary in light of broader research traditions and politics around the contestation of inequality in Japan, yet expressed uncertainties about what specifically was being measured through its use. In the Soma Region, no statistically significant associations were found between JSADI-defined deprivation and the likelihood of having diabetes, with quantitative results failing to demonstrate a gradient across deprivation quartiles. Classifications of area-level inequality produced through use of the JSADI did not resonate with local understandings and experiences, with lay actors giving accounts of aspects of social inequalities that were meaningful to them but not reflected in the products of the JSADI. This thesis brings these threads together to argue that use of the JSADI has unclear meaning for assessing social inequalities in health in the Soma Region. In identifying how the meaning attached to one indicator can differ for different groups of stakeholders in the research process, this thesis makes the case for a more critical examination of the indicators used in health inequalities research and their application in different contexts and fields.