It is well known that area-level socioeconomic conditions have a contextual association with an individual’s health outcomes [1–3]. Many studies have indicated that area-level deprivation, which reflects various aspects of an area’s socioeconomic positions, can affect the health outcomes of its residents, including mortality [4–7], morbidity [8–11], mental health [12, 13], poor birth outcomes [14–16], and health risk behavior [17, 18]. The impact of area-level deprivation on health matters for not only public health policies but also macroeconomic and social policies, which are committed to income redistribution, labor market regulations, and other issues related to social welfare.
To capture small-area socioeconomic deprivation, a variety of deprivation measures have been developed [19, 20]. These measures generally cover multiple dimensions of deprivation, such as income, employment, education, social class, and housing conditions. To construct a single index of deprivation, the most straightforward way is to sum standardized scores (z-scores) of each dimension with an equal weight (e.g., Townsend and Carstairs indices [21, 22]) or different weights (e.g., Jarman index [23]). To avoid normative judgment that is inevitably involved in any weighting, the principal component and factor analysis approaches, which assign a set of weights that statistically best explain the variation in the data, have also been often used [24–26]. Because all of these approaches are known to have both advantages and disadvantages and have no clear theoretical background [19], it may be useful to compare their results and assess their robustness.
Regarding the association between area-level deprivation and health, two issues have remained to be addressed. First, the impact on self-rated health (SRH), which represents overall health conditions [27, 28], or subjective well-being (SWB), which is often expressed by life satisfaction (LS) [29, 30], has been relatively understudied, compared to the impact of area-level deprivation on mortality, morbidity, or other specific health outcomes [4–17]. Meanwhile, many studies have examined the association between area-level income inequality or poverty and an individual’s SRH or SWB [31–33]. Hence, it is of interest to know whether the same is true for area-level deprivation, which captures other domains of area-level socioeconomic positions rather than just income.
Second, the factors that may mediate the impact of area-level deprivation on SRH and LS need to be more addressed. Specific factors such as the availability of alcohol, the physical environment, and maternal health have been found to mediate the impact of neighborhood deprivation on alcohol consumption, some health biomarkers, and preterm birth, respectively [34, 35, 16]. In the case of the impact on SRH and SWB, health behavior and/or interactions with neighbors/friends, both of which are well known to affect them [36–39], could be potential mediators. In particular, the mediating effect of health behavior, if any, would have an important policy implication because public policies for healthy lifestyle promotion could then be expected to mitigate the adverse impact of area-level deprivation.
Keeping these issues in mind, this study conducted a multilevel analysis to examine how an individual’s SRH and LS were associated with municipality-level deprivation in Japan, where regional disparities in health resumed a widening trend in the mid-1990s [40, 41]. An increasing number of studies have examined the importance of area-level socioeconomic conditions as a contextual determinant of health among Japanese people. Specifically, some studies examined how municipality-level socioeconomic positions are associated with mortality or life expectancy [4], while other studies investigated how neighborhood deprivation is related to all-cause mortality [6], as well as the risk of incidence, mortality, and survival from cancers [11]. However, more investigation into its impact on SRH or LS as well as its potential mediators is needed for a more comprehensive understanding of the relevance of area-level deprivation for an individual’s well-being.