(Re)conceptualizing vulnerability in health under the syndemics perspective: protocol for a scoping review

Introduction

In the last decades, the concept of vulnerability has been widely used in global health research to assess susceptibility to diseases and disasters in individuals and groups. Along with its increasing use, its polysemous character and scope have become more evident. Patterns and variations of this concept within the health field are articulated around historical contexts, conjunctural circumstances, lifetime trajectories, individual risk factors, and conditions of exposure to specific pathogenic agents (Wardrop et al., 2021). Although vulnerability is now recognized as a dynamic trait compounded by biomedical, social, and environmental dynamics, sanitary perspectives —particularly focused on individual vulnerability to disease-specific risk factors—have substantially informed research on this area (Hufschmidt, 2011; Osborne et al., 2021). While adding a vulnerability angle has proven to be useful to bring attention to the unequal distribution of the risks to and consequences of diseases and disasters (Faas, 2016), this perspective is often insufficient to explain interactions between environmental, zoonotic, and social dynamics in the generation of health and disease (Jeleff et al., 2022). Moreover, labeling specific groups and vast geographical areas under the category of ‘vulnerable’ seems to have been more blurring than illuminating in terms of the actual capacity of this concept to explain the realities of those covered by it, acknowledge their responses generated under unfavorable conditions, and counter the dynamics of marginalization and exclusion originating such vulnerability in the first place (Marino & Faas, 2020).

Theoretical arguments developed around the concepts of structural vulnerability (Holmes, 2011), structural violence (Farmer, 1996), and syndemics (Singer, 2009), have explored these underlying factors and interactions. The concept of ‘syndemics’, in particular, seems to have special traction. This perspective intends to explore how synergistic interactions between two or more diseases under specific social conditions can negatively affect the mutual course of each disease trajectory, and, consequently, enhance vulnerability and health inequities (Brazil, 2022; Sharma, 2017; Singer et al., 2017). Core to this concept is the identification of a bio-social interface, understood as the intersection in which social and environmental arrangements structurally linked to the overlap of diseases can cause or exacerbate their occurrence (Singer et al., 2020).

Since its first inception, the concept of vulnerability was constitutive of this approach, as social factors have been usually presented as generators or instigators of heightened vulnerability in particular social groups and contexts (Mendenhall et al., 2017; Singer, 2009; Singer et al., 2020; Sharma, 2017). The idea of ‘syndemic vulnerability’, specifically, links both concepts by alluding to the integration of “epidemiological and experiential levels of analysis of multiple, overlapping social and health problems that increase morbidity and mortality as a result of syndemic clustering of social and health conditions within a certain context” (Singer et al., 2017). This specific variation has been used to bring forward issues of power-sustaining inequities involved in the clustering of diseases and risk factors (Singer & Rylko-Bauer, 2021).

What seems to be the most important contribution of the syndemics perspective to public health practice, i.e., applying a systemic perspective to understand health and disease (Hossain et al., 2022; Mendenhall et al., 2022; Newfield, 2022), has come into question in the last years. Recent critiques to syndemics’ research have alerted of the danger of generating diffuse predictions based on the assumption of mutually reinforcing factors for which interactions cannot be clearly described (Tsai, 2018), as well as the persistent practice of applying biomedical lenses to describe specific contexts in terms of risks (Weaver & Kaiser, 2022), while ignoring other layers of complexity also emerging from said contexts (Slagboom et al., 2022). Similarly, researchers have claimed that there is still much to learn about the specific ways in which environmental, economic, cultural, and social factors interact to create high-risk contexts for overlapping health conditions (Mendenhall et al., 2017; Willen et al., 2017). In 2020, a scoping review found that most articles on syndemic interactions published between 2015 and 2019 described the influence of social determinants such as poverty, inequity, and racism on the clustering of diseases or disease outcomes (Singer et al., 2020). The same review, however, recognized that the articulation of those factors in relation to disease trajectories just starts to be understood (Nichter, 2016; Singer et al., 2020).

This scoping review acknowledges the potential to continue improving the scientific literature on syndemics, particularly about the systemic nature of vulnerability in health. One of the reasons to consider the current relevance of this approach is the extensive use of the syndemics perspective in the study of the overlapping biomedical and socio-economic conditions exacerbating the impacts of the coronavirus disease 2019 (COVID-19) pandemic around the world (McMahon, 2021). The interactions of the infection with pre-existing chronic diseases, their articulation with environmental factors (Yadav et al., 2020), and the early impacts of COVID-19 in marginalized or socially excluded groups (Gravlee, 2020; Lund, 2020; Selden & Berdahl, 2020) have brought a new impetus to syndemics’ research (Poteat et al., 2020; Singer & Rylko-Bauer, 2021), which we are interested in further exploring.

With this review, we intend to systematically explore the contributions of the syndemics perspective to conceptualizations of vulnerability articulated during the COVID-19 pandemic. We intend to do so by identifying social and environmental arrangements so far described in syndemic research published since December 2019 and their associations with the idea of vulnerability. In first place, interactions among diseases and health conditions, species, social factors; and environmental dynamics so far described in the literature will be examined. Subsequently, we will focus on bio-social interactions and will capture variations in the explanations provided about the role played by those socio-environmental dynamics in the observed interactions in relation to populations, settings, and interacting conditions. Finally, we will track the contributions and limitations of the syndemics perspective to the study of vulnerability in health in light of the evidence produced around COVID-19.

Methods

Data availability

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