The COVID-19 pandemic has exposed deep geographic, racial, and economic inequalities in the U.S. and globally and has served as a reminder of the inseparable links between biological and social processes in people’s health. This lesson is not specific to COVID-19, but has been at the center of understanding the mechanisms of disparities in chronic diseases such as HIV, diabetes, and tuberculosis for decades. Syndemic theory , which describes clustered and synergistically related epidemics arising from harmful social conditions, provides a useful framework for understanding these complex relationships, and its application to clinical care, research, and health policies focused on acute diseases can provide valuable information.
Syndemic theory, with its roots in medical anthropology, has been revolutionary for progress in addressing other major public health challenges, but to date it has been applied almost exclusively to chronic conditions. This is possibly due to its origin in describing patterns of HIV disparity at the community level and its historical application to conditions that have been more clearly understood to be related to modifiable behaviors such as substance use or diet. However, many benefits could be gained from applying syndemic theory to acute conditions. This viewpoint looks at 2 specific examples: sepsis and COVID-19, although other major acute medical conditions such as trauma, stroke,
Why apply syndemic theory to complex systems?
Syndemic theory focuses on adverse interactions between diseases and social conditions, specifically drawing attention to the mechanisms of these interactions. The identification of syndemic interactions allows a new way of understanding the prevention and treatment of the conditions involved.
For example, it may become clear that mortality from condition A cannot be reduced without addressing condition B, or that condition B can be almost completely prevented by appropriate treatment of condition C. Syndemic frameworks have had a important role in informing the response to major public health challenges, such as the SAVA (substance abuse, violence, and AIDS) syndemic in urban communities in the United States. Using a syndemic framework, the researchers identified subsets of HIV-infected patients who had poor outcomes not predicted by their viral characteristics but based on characteristics of the other elements of the syndemic.
For example, syndemic analysis demonstrated that high SAVA scores were associated with higher HIV viral loads and decreased effectiveness of antiretroviral treatment. This information directly informed a randomized clinical trial that demonstrated reductions in HIV viral load among people who use illicit drugs and enrolled in a treatment program that reinforces abstinence.
Application of syndemic theory to acute conditions
Acute conditions often serve as sentinel indicators of complex and enduring relationships between forces that influence an individual’s health. By providing a framework of disease-disease and social condition-disease interactions, syndemic theory can improve the understanding of acute health conditions within a specific population and could lead to key scientific advances in a way that isolated research and specific conditions has not done so.
Sepsis
Sepsis , a massive global health problem with nearly 50 million cases worldwide each year despite incalculable clinical, research, advocacy, education and financial investments aimed at reducing its incidence, is an ideal acute health condition to which to apply a syndemic framework.
Although sepsis is a challenge almost everywhere in the world, certain groups of people are at much higher risk than others. The risk of sepsis in the US is primarily driven by aging and multimorbidity, the coexistence of 2 or more chronic conditions. In the US, these risk factors are closely related and clustered geographically.
Despite a rich body of science on sepsis risk factors, most previous studies have focused on an individual’s personal health history, sociodemographic characteristics, or community characteristics in isolation, without evaluating the complex and spatially structured relationships between them. This has been due in part to data limitations, such that individual data sources are insufficient to assess all relevant risk factors together, as well as the lack of a sufficient conceptual framework .
Sepsis, multimorbidity, aging, and low access to and quality of health care exist within a network of complex social and biological relationships, a pattern that strongly suggests a syndemic . A deeper understanding of these relationships may improve understanding of factors that influence individual sepsis risk.
For example, the ability to better assess the sepsis risk profile of patients with multimorbidity and social risk factors before they acquire an acute infection could lead to targeted sepsis prevention efforts, such as intensive pneumococcal vaccination campaigns or research. improved information on ways to modify the relationship between the environment and the inflammatory response to acute infection.
COVID-19
COVID-19 is a second example of the potential usefulness of a syndemic framework with an acute health condition. Globally, the relationships between COVID-19, chronic comorbidities and social conditions have led to the proposal to consider some of these elements as part of a syndemic.
As syndemics are, by nature, specific to local populations, it has become clear that racial and ethnic factors and racism are among the strongest social forces driving COVID-19 disparities in the US. The relationship between racism and COVID-19 is multifaceted, and factors such as access to vaccines, working conditions and exposure through employment in essential sectors, and biological conditions such as obesity (which in turn have critical links to social factors in the US) played key roles.
Although these are just simplified examples of the complex systems that influence COVID-19 incidence, mortality, and morbidity in the US, they highlight the ways in which a syndemic approach to acute diseases like COVID-19 can be useful. For example, despite the remarkable rapid development of multiple highly effective vaccines against SARS-CoV-2, optimal societal benefit from vaccines requires understanding and effectively addressing the causal mechanisms that influence vaccine delivery and uptake.
Syndemic Frameworks and the Way Forward for Acute Care Research and Health Policy
Using a syndemic approach to acute medical conditions enables critical improvements in understanding causality , disease prevention, and overall health. Acute health conditions exist within complex, community-specific syndemic relationships. To harness this information and translate it into practical improvements in the prevention and treatment of acute illnesses, the medical and public health communities should take the following steps:
Identify the fundamental social and biological conditions involved in complex acute disease systems within specific contexts of place and time. This will require linking multiple data sources at the individual and community levels. Administrators at major health plans and state and federal government agencies will be essential in facilitating this type of data linkage and fostering data access and collaboration. Clinicians have an important role in working with patients to identify the key social and biological processes that affect their patients’ health.
Assess key relationships between these conditions, including causal mechanisms and feedback loops , using community-informed research methods. Multilevel modeling is a well-established approach for evaluating syndemic relationships. Agent-based modeling, a simulation model in which outcomes are determined by the local actions and interactions of agents within an environment, and geospatial analysis may be particularly useful methods. Researchers and clinicians must collaborate across traditionally isolated disciplines and fields of medicine to evaluate important disease-disease interactions.
Investigate ways to change the complex system of risk factors and forces that influence acute illness and introduce new ways of thinking about prevention and intervention. These assessments may reveal that prioritizing key elements of the system could have significant downstream effects on other components without having to address them all at once, with some elements essentially acting as levers or blockers. Through new research and community collaborations, it may become clear that a seemingly ineffective intervention tested in one population or outcome can be effective when tested in a different set of circumstances.
Syndemic frameworks can help identify or improve the effectiveness and efficiency of a new medical or policy intervention and can be powerful tools for social justice in health. It is time for researchers, clinicians, and health policy professionals focused on acute medical conditions to embrace the complex systems in which they and patients exist and leverage a syndemic approach to improve the health of communities.
