Background

The Social Determinants of Health (SDH) literature has long reported a consistent economic status-health gradient1: the richer are healthier than the poor, and this relation is maintained after adjusting for traditional risk factors (eg, blood pressure, cholesterol). However, a range of inconsistent and seemingly counter-intuitive findings in Migrants’ Health (MH) research defy that expectation. If the richer are supposed to be healthier and the poorer sicker, why do migrants often display similar or better health outcomes than locals despite frequent socioeconomic disadvantage and barriers to healthcare use? (Healthy migrant paradox); why don't they reap the expected health benefits associated to an improved economic status? (Diminishing returns paradox) and why are migrants living in low income enclaves characterised by high ethnic density sometimes healthier than those in more affluent neighbourhoods? (Ethnic density paradox). The frequent reporting of these disconcerting findings (box)2–22 suggests that the relation between socioeconomic status and health does not always behave as expected for migrants and their descendants. Between the lines of these paradoxes lies a concern that the focus on reducing socioeconomic inequalities that prevails in SDH research is insufficient to respond to the health needs of an increasingly diverse society.

Limitations of current approaches

The healthy migrant, diminishing returns and ethnic density paradoxes have received substantial research attention but the evidence for these puzzling findings is inconsistent and drawn from studies that face a number of limitations. Although MH research is paying increasing attention to diseases that are also common in the majority population, many MH studies focus exclusively on migrant-specific diseases, and the explanatory factors examined are often reduced to cultural differences, poor knowledge and wrong behaviours.17 23 So far, this field of research has paid insufficient attention to the most frequent health problems that affect migrants—often similar to those faced by autochthonous—and how these relate to occupational, legislative, social and environmental factors (the broader SDH).17 24 A large body of research has compared the health of migrants versus autochthonous within a single country, but there are few cross-country comparisons of similar ethno/national groups.25 26 SDH research, in turn, often eludes vexed issues related to racial hierarchies and the stigmatisation of minorities on ethnic/religious grounds.24 27 28

Both strains of research rely heavily on indicators of questionable validity. MH studies pragmatically employ overarching ethno/national statistical categories that do not capture the multiple layers of diversity that exist within traditional classifications17 29 and that become increasingly obsolete as mixed-ethnicity populations grow. Subjective measures of self-rated health are commonly used as a robust indicator of health status, although the meaning of excellent, fair or poor health is largely influenced by cultural contexts.30 31 SDH studies, in turn, often rely on conventional indicators of socioeconomic status (eg, occupational class, income, education) that do not measure accurately the economic status of migrants—whose personal income often fluctuates and relates poorly to educational levels32—and that miss less tangible dimensions of subjective social status (eg, participation, prestige) that also predict health outcomes.33

The scant interactions between SDH and MH research—and their insufficient engagement with the social sciences—have hampered progress in advancing our understanding of paradoxical research results. A matter of outmost concern is that most MH studies remain largely untheorised.22 Recent conceptual advancement has accounted for different migratory stages,34 adopted a life-course approach19 and accounted for the SDH.35 Still, no mid-range theories have so far linked the general abstract concepts of macro theories with the grounded experiential knowledge of lay people in everyday settings.

A transdisciplinary research agenda

The striking discrepancies between SDH and MH research calls for a transdisciplinary approach that brings together these long-standing parallel strains of research, draws from and contributes to theoretical insights from the social sciences and bridges academic disciplinary expertise with the everyday life experiential knowledge of lay people.

To unravel migrants’ health paradoxes, it will be imperative to problematise univocal paradigms in predominantly quantitative research traditions and unpack the social significance of commonly used statistical categories and indicators. Researchers must revisit the assumption implicit in most MH studies that a shared ethnicity/place of origin confers fundamental homogeneity to populations that differ widely and fundamental heterogeneity versus de local general population. Future studies should acknowledge that people develop fluid and many-layered identities to function in increasingly diverse urban milieus where established migrants and their descendants, mixed-ethnicity persons, newly arriving populations, autochthonous ethnic minorities (eg, Roma) and whites interact with each other, and that such interactions frame mental schemes and health perceptions. Similarly, future SDH research should transcend the current focus on socioeconomic status and consider measures of social status that capture more precisely the position of migrants and their descendants in the social hierarchy, including broad structural factors (eg, migration and occupational policies) and super-structural determinants linked to historical processes and the ethnically patterned unequal distribution of power and resources.

Migrant populations are often portrayed in the media and some medical circles as carriers of infections. The argument that diseases travel in migrants’ blood may fuel discriminative attitudes related to fears of increased transmission of communicable infections, burden on health expenditures and other costs to welfare. The recent rise of the Law and Justice party in Poland—who claimed during the 2015 electoral campaign that Syrian asylum seekers were bringing in cholera—is an illustrative example of how political parties can successfully capitalise on epidemiological arguments to advance the antimigrant political agenda. At a time of growing tensions between new populations desperately trying to reach Europe and increasing antimigrant sentiments nourished by the presumed epidemiological, cultural, economic and security threats that migrants pose, a more positive portray of the ethnic and religious diversity of our societies is urgently needed. So far, MH research has mostly focused on migrants’ health disadvantages with scant attention to populations faring unexpectedly well. A better understanding of how health-protective assets are acquired and maintained over time could yield valuable lessons about how to protect the health of migrants, their descendants and populations as a whole. The limited role of classical risk factors in explaining the socioeconomic health gradient has already shifted some scholarly attention towards the assets that individuals and communities possess: optimism, self-esteem and self-efficacy—it is argued—are psychological assets that confer resilience and protect health.36 A major caveat intrinsic to this approach is the construction of a psychological ideal (possession of resilience) that labels deviation from this model as maladaptive. It becomes increasingly important to describe the practices and contexts in which some migrants retain their initial health advantage. This would shed light into the contingent conditions that foster/hinder health for different people in different contexts, broadening the current public health focus on individuals’ behaviour and psychological skills.

Disentangling closely related determinants in statistical models (eg, ethnicity and socioeconomic status) is challenging. Is socioeconomic status a confounder in the relationship between ethnicity and health or is it on the causal pathway between ethnicity and health?24 Are the effects of, for example, gender, socioeconomic status and ethnicity additive or is there evidence of intersectionality where an individual's health is ‘not simply the sum of their parts’?37 What is the relationship between migration-related variables such as length of migration and reason for migration and health indicators? Longitudinal population health studies, with theoretically informed statistical modelling frameworks, are needed to examine the so far inconsistently documented ‘migrant health paradoxes’ and provide objective measurements of health across diverse population groups over time.

Theory-generating qualitative inquiries and case study research anchored in real-life situations are promising avenues to unpack the social processes that underlie unexpected socioeconomic health gradients in migrants and their descendants. The inductive and iterative approach used in qualitative research—with open-ended questions that give participants the opportunity to respond in their own words as opposed to forcing them to choose from fixed responses—may well reveal that what is framed as paradoxical by researchers has a logical explanation from an insider (emic) perspective. Drawing from and contributing to the Sociology of Health and Illness, Medical Anthropology and Ethnicity Studies, rigorous qualitative studies shall provide a more holistic and nuanced understanding of how mobility, ethnicity, religious affiliation, income, legislative status, employment status, working conditions, neighbourhood characteristics, gender relations and social status intersect with other SDH, demographic variables and policy contexts to influence the health of migrants and their descendants. By assessing the significance of commonly employed categories of ethnicity, unpacking broad variables into finer constructs and contextualising individuals’ lived experiences, qualitative social scientists could contribute to the theoretical framework for modelling, generate fresh hypothesis to be tested and inform valid and reliable measurement, thus providing a solid base from which quantitative researchers can interpret their findings and operationalise key concepts in future studies.

As participatory and co-creation approaches gain momentum, the establishment of academic–community partnerships holds the promise of maximising communities’ ownership over research outcomes and the potential for its translation into practice. While a number of success histories avail the enormous positive potential of community-based participatory research, important caveats caution against romanticising the approach. Early participatory research with migrants has shown that to genuinely engage lay people at the analytical level and sustain their participation over time is in practice a complex and costly process.38 The assumption that participation per se will empower participants overlooks potential feelings of disappointment and/or exploitation amidst power unbalances, vested interest and community representativeness issues. To maximise the potential of community engagement and co-creation as key drivers of innovation and as essential ingredients to improve policies, researchers will need to experiment with new ways of bringing people and disciplines together. The assumption that migrants and their descendants will contribute to lengthy processes of knowledge production is a risky standpoint that demands critical insights into the opportunities, limitations and challenges posed by participatory approaches. A substantial amount of effort, time and resources will need to be directed into addressing major practical, conceptual and ethical challenges. The potential for a paradigm shift from a pathogenic deficit model that sees migrants as a burden to their reconceptualisation as actively engaged citizens clearly deserves this effort.