Invited Commentary: What Social Epidemiology Brings to the Table-Reconciling Social Epidemiology and Causal Inference

Theorizing epidemiology, the stories bodies tell, and embodied truths: a status update on contending 21st c CE epidemiological theories of disease distribution

This critical review considers the status of 21st-century epidemiological theories of disease distribution, updating to 2024 prior analyses published up through 2014, and discusses the implications of these theories for research, practice, and pedagogy. Three key trends stand out: (a) the continued dominance of individualistic biomedical and lifestyle theories; (b) growth and elaboration of social epidemiological alternatives; and (c) the ongoing inattention to epidemiologic theories of disease distribution in the training of epidemiologists and public health professionals and in current efforts to improve the rigor of epidemiological research and causal inference. In a context of growing global political polarization, climate crisis, broader environmental and ecological crises, and stubbornly persistent health inequities within and between nations, producing actionable knowledge relevant to improving the people's health and advancing health justice will require much greater engagement with social epidemiologic theories of disease distribution in research, pedagogy, and practice. At issue is critically engaging with the embodied truths manifested in the stories bodies tell in population patterns of health, disease, and well-being.

Defining Spatial Epidemiology: A Systematic Review and Re-orientation

BACKGROUND

Spatial epidemiology has emerged as an important subfield of epidemiology over the past quarter century. We trace the origins of spatial epidemiology and note that its emergence coincided with technological developments in spatial statistics and geography. We hypothesize that spatial epidemiology makes important contributions to descriptive epidemiology and analytic risk-factor studies but is not yet aligned with epidemiology's current focus on causal inference and intervention.

METHODS

We conducted a systematic review of studies indexed in PubMed that used the term "spatial epidemiolog*" in the title, abstract, or keywords. Excluded articles were not written in English, examined disease in animals, or reported biologic pathogen distribution only. We coded the included papers into five categories (review, demonstration of method, descriptive, analytic, and intervention) and recorded the unit of analysis (i.e., individual vs. ecological). We additionally examined articles coded as analytic ecologic studies using scales for lexical content.

RESULTS

A total of 482 articles met the inclusion criteria, including 76 reviews, 117 demonstrations of methods, 122 descriptive studies, 167 analytic studies, and 0 intervention studies. Demonstration studies were most common from 2006 to 2014, and analytic studies were most common after 2015. Among the analytic ecologic studies, those published in later years used more terms relevant to spatial statistics (incidence rate ratio =1.3; 95% confidence interval [CI] = 1.1, 1.5) and causal inference (incidence rate ratio =1.1; 95% CI = 1.1, 1.2).

CONCLUSIONS

Spatial epidemiology is an important and growing subfield of epidemiology. We suggest a re-orientation to help align its practice with the goals of contemporary epidemiology.

Selection Bias in Health Research: Quantifying, Eliminating, or Exacerbating Health Disparities?

Purpose of review

To summarize recent literature on selection bias in disparities research addressing either descriptive or causal questions, with examples from dementia research.

Recent findings

Defining a clear estimand, including the target population, is essential to assess whether generalizability bias or collider-stratification bias are threats to inferences. Selection bias in disparities research can result from sampling strategies, differential inclusion pipelines, loss to follow-up, and competing events. If competing events occur, several potentially relevant estimands can be estimated under different assumptions, with different interpretations. The apparent magnitude of a disparity can differ substantially based on the chosen estimand. Both randomized and observational studies may misrepresent health disparities or heterogeneity in treatment effects if they are not based on a known sampling scheme.

Conclusion

Researchers have recently made substantial progress in conceptualization and methods related to selection bias. This progress will improve the relevance of both descriptive and causal health disparities research.

Racial and Ethnic Inequities in Health: Examining the Contributions of the American Journal of Epidemiology to Advancing the Science

The perverseness of racial and ethnic inequities in the United States continues to implore the investigation of their causes. While there have been improvements in the health of the US population, these improvements have not been equally distributed. To commemorate the 100th anniversary of the American Journal of Epidemiology, in this commentary, we aim to highlight the Journal's contributions to: 1) the definition and use of race and ethnicity in research, and 2) understanding racial and ethnic inequities, both empirically and methodologically, over the past decade. We commend the Journal for its contributions and for spearheading many of the challenges related to measuring and interpreting racial and ethnic data for the past 20 years. We identify 3 additional areas in which the Journal could make further impact to address racial and ethnic inequities: 1) devote a section in every issue of the Journal to scientific papers that make substantive epidemiologic or methodological contributions to racial and ethnic inequities in health; 2) update the Journal's guidelines for authors to include justifying the use of race and ethnicity; and 3) diversify the field of epidemiology by bringing a new cadre of scholars from minoritized racial and ethnic groups who represent the most affected communities into the research process.

Structural racism theory, measurement, and methods: A scoping review

Introduction

Epidemiologic and public health interest in structural racism has grown dramatically, producing both increasingly sophisticated questions, methods, and findings, coupled with concerns of atheoretical and ahistorical approaches that often leave the actual production of health or disease ambiguous. This trajectory raises concerns as investigators adopt the term "structural racism" without engaging with theories and scholars with a long history in this area. This scoping review aims to build upon recent work by identifying current themes about the incorporation of structural racism into (social) epidemiologic research and practice with respect to theory, measurement, and practices and methods for trainees and public health researchers who are not already deeply grounded in this work.

Methods

This review uses methodological framework and includes peer-review articles written in English published between January 2000-August 2022.

Results

A search of Google Scholar, manual collection, and referenced lists identified a total of 235 articles; 138 met the inclusion criteria after duplicates were removed. Results were extracted by, and organized into, three broad sections: theory, construct measurement, and study practice and methods, with several themes summarized in each section.

Discussion

This review concludes with a summary of recommendations derived from our scoping review and a call to action echoing previous literature to resist an uncritical and superficial adoption of "structural racism" without attention to already existing scholarship and recommendations put forth by experts in the field.

An Umbrella Review of the Links Between Adverse Childhood Experiences and Substance Misuse: What, Why, and Where Do We Go from Here?

BACKGROUND AND OBJECTIVES

A wealth of research has identified adverse childhood experiences (ACEs; abuse, neglect, violence or disorder in the home) as a strong risk factor for substance misuse. Synthesis of the existing evidence is critical to shape policy and inform directions for future research. Existing reviews have focused on specific substances or substance use outcomes (eg, disorder), and do not include discussion of the mechanisms that operate between ACEs and substance misuse. The current umbrella review aims to synthesize reviews on the relationship between ACEs and substance misuse, review the evidence on the mechanisms linking these, identify existing gaps in our knowledge, and discuss critical directions for future research, practice, and public policy.

METHODS

Two electronic databases (PsycINFO and Medline) were searched for reviews published between 1998 and 2022 on the link between ACEs and substance misuse. Twenty articles met eligibility criteria and were qualitatively synthesized.

RESULTS

Results overwhelmingly demonstrated an elevated risk of substance misuse or disorder, among adolescents and adults exposed to ACEs. Research on the mechanisms that explain this link highlights a multitude of potential intervention targets, with childhood stress propelling a cascade of effects across neurobiological, endocrine, immune, metabolic, and nervous systems, impacting psychosocial and cognitive functioning. Nonetheless, the literature is subject to limitations surrounding potential unmeasured cofounders and causality, as well as decontextualizing childhood adversity from broader structural issues that influence the link between ACEs and substance misuse. Research, policy, and practice that seek to holistically understand and address the relationship between ACEs and substance misuse within the broader social determinants of health is crucial.

Invited Commentary: Conducting and Emulating Trials to Study Effects of Social Interventions

All else being equal, if we had 1 causal effect we wished to estimate, we would conduct a randomized trial with a protocol that mapped onto that causal question, or we would attempt to emulate that target trial with observational data. However, studying the social determinants of health often means there are not just 1 but several causal contrasts of simultaneous interest and importance, and each of these related but distinct causal questions may have varying degrees of feasibility in conducting trials. With this in mind, we discuss challenges and opportunities that arise when conducting and emulating such trials. We describe designing trials with the simultaneous goals of estimating the intention-to-treat effect, the per-protocol effect, effects of alternative protocols or joint interventions, effects within subgroups, and effects under interference, and we describe ways to make the most of all feasible randomized trials and emulated trials using observational data. Our comments are grounded in the study results of Courtin et al. (Am J Epidemiol. 2022;191(8):1444-1452).

Structural Racism and Quantitative Causal Inference: A Life Course Mediation Framework for Decomposing Racial Health Disparities

Quantitative studies of racial health disparities often use static measures of self-reported race and conventional regression estimators, which critics argue is inconsistent with social-constructivist theories of race, racialization, and racism. We demonstrate an alternative counterfactual approach to explain how multiple racialized systems dynamically shape health over time, examining racial inequities in cardiometabolic risk in the National Longitudinal Study of Adolescent to Adult Health. This framework accounts for the dynamics of time-varying confounding and mediation that is required in operationalizing a "race" variable as part of a social process (racism) rather than a separable, individual characteristic. We decompose the observed disparity into three types of effects: a controlled direct effect ("unobserved racism"), proportions attributable to interaction ("racial discrimination"), and pure indirect effects ("emergent discrimination"). We discuss the limitations of counterfactual approaches while highlighting how they can be combined with critical theories to quantify how interlocking systems produce racial health inequities.

Advancing the Social Epidemiology Mission of the American Journal of Epidemiology

Social epidemiology is concerned with how social forces influence population health. Rather than focusing on a single disease (as in cancer or cardiovascular epidemiology) or a single type of exposure (e.g., nutritional epidemiology), social epidemiology encompasses all the social and economic determinants of health, both historical and contemporary. These include features of social and physical environments, the network of relationships in a society, and the institutions, politics, policies, norms and cultures that shape all of these forces. This commentary presents the perspective of several editors at the Journal with expertise in social epidemiology. We articulate our thinking to encourage submissions to the Journal that: 1) expand knowledge of emerging and underresearched social determinants of population health; 2) advance new empirical evidence on the determinants of health inequities and solutions to advance health equity; 3) generate evidence to inform the translation of research on social determinants of health into public health impact; 4) contribute to innovation in methods to improve the rigor and relevance of social epidemiology; and 5) encourage critical self-reflection on the direction, challenges, successes, and failures of the field.

Conceptualizing, Contextualizing, and Operationalizing Race in Quantitative Health Sciences Research

Differences in health outcomes across racial groups are among the most commonly reported findings in health disparities research. Often, these studies do not explicitly connect observed disparities to mechanisms of systemic racism that drive adverse health outcomes among racialized and other marginalized groups in the United States. Without this connection, investigators inadvertently support harmful narratives of biologic essentialism or cultural inferiority that pathologize racial identities and inhibit health equity. This paper outlines pitfalls in the conceptualization, contextualization, and operationalization of race in quantitative population health research and provides recommendations on how to appropriately engage in scientific inquiry aimed at understanding racial health inequities. Race should not be used as a measure of biologic difference, but rather as a proxy for exposure to systemic racism. Future studies should go beyond this proxy use and directly measure racism and its health impacts.VISUAL ABSTRACTAppeared as Annals "Online First" article.

Social Epidemiology: Past, Present, and Future

In a context where epidemiologic research has been heavily influenced by a biomedical and individualistic approach, the naming of “social epidemiology” allowed explicit emphasis on the social production of disease as a powerful explanatory paradigm and as critically important for interventions to improve population health. This review briefly highlights key substantive areas of focus in social epidemiology over the past 30 years, reflects on major advances and insights, and identifies challenges and possible future directions. Future opportunities for social epidemiology include grounding research in theoretically based and systemic conceptual models of the fundamental social drivers of health; implementing a scientifically rigorous yet realistic approach to drawing conclusions about social causes; using complementary methods to generate valid explanations and identify effective actions; leveraging the power of harmonization, replication, and big data; extending interdisciplinarity and diversity; advancing emerging critical approaches to understanding the health impacts of systemic racism and its policy implications; going global; and embracing a broad approach to generating socially useful research.

Expected final online publication date for the Annual Review of Public Health, Volume 43 is April 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Mediation effects that emulate a target randomised trial: Simulation-based evaluation of ill-defined interventions on multiple mediators

Many epidemiological questions concern potential interventions to alter the pathways presumed to mediate an association. For example, we consider a study that investigates the benefit of interventions in young adulthood for ameliorating the poorer mid-life psychosocial outcomes of adolescent self-harmers relative to their healthy peers. Two methodological challenges arise. First, mediation methods have hitherto mostly focused on the elusive task of discovering pathways, rather than on the evaluation of mediator interventions. Second, the complexity of such questions is invariably such that there are no well-defined mediator interventions (i.e. actual treatments, programs, etc.) for which data exist on the relevant populations, outcomes and time-spans of interest. Instead, researchers must rely on exposure (non-intervention) data, that is, on mediator measures such as depression symptoms for which the actual interventions that one might implement to alter them are not well defined. We propose a novel framework that addresses these challenges by defining mediation effects that map to a target trial of hypothetical interventions targeting multiple mediators for which we simulate the effects. Specifically, we specify a target trial addressing three policy-relevant questions, regarding the impacts of hypothetical interventions that would shift the mediators' distributions (separately under various interdependence assumptions, jointly or sequentially) to user-specified distributions that can be emulated with the observed data. We then define novel interventional effects that map to this trial, simulating shifts by setting mediators to random draws from those distributions. We show that estimation using a g-computation method is possible under an expanded set of causal assumptions relative to inference with well-defined interventions, which reflects the lower level of evidence that is expected with ill-defined interventions. Application to the self-harm example in the Victorian Adolescent Health Cohort Study illustrates the value of our proposal for informing the design and evaluation of actual interventions in the future.