Concept in epidemiology
Syndemics is the evaluation of how social and health conditions arise, in what ways they interact, and what upstream drivers may produce their interactions. The word is a blend of "synergy" and "epidemics". The idea of syndemics is that no disease exists in isolation and that often population health can be understood through a confluence of factors (such as climate change or social inequality) that produces multiple health conditions that afflict some populations and not others. Syndemics are not like pandemics (where the same social forces produce clustered conditions equally around the world); instead, syndemics reflect population-level trends within certain states, regions, cities, or towns.
A syndemic or synergistic epidemic is generally understood to be the aggregation of two or more concurrent or sequential epidemics or disease clusters in a population with biological interactions, which exacerbate the prognosis and burden of disease. The term was developed by Merrill Singer in the early 1990s to call attention to the synergistic nature of the health and social problems facing the poor and underserved. Syndemics develop under health disparity, caused by poverty, stress, climate, or structural violence and are studied by epidemiologists and medical anthropologists concerned with public health, community health and the effects of social conditions on health. The concept was translated from anthropology to a larger audience in 2017, with the publication of a Series on Syndemics in "The Lancet", led by Emily Mendenhall.
The syndemic approach departs from the biomedical approach to diseases to diagnostically isolate, study, and treat diseases as distinct entities separate from other diseases and independent of social contexts.
Definition.
A syndemic is a synergistic epidemic. The term was developed by Merrill Singer in the mid-1990s, culminating in a 2009 textbook. Disease concentration, disease interaction, and their underlying social forces are the core concepts.
Disease co-occurrence, with or without interactions, is known as comorbidity and coinfection. The difference between "comorbid" and "syndemic" is per Mustanski et al. "comorbidity research tends to focus on the nosological issues of boundaries and overlap of diagnoses, while syndemic research focuses on communities experiencing co-occurring epidemics that additively increase negative health consequences." It is possible for two afflictions to be comorbid, but not syndemic i.e., the disorders are not epidemic in the studied population, or their co-occurrence does not cause an interaction that then contributes to worsened health. Two or more diseases can be comorbid without interactions, or interaction occurs but it is beneficial, not deleterious. "Syndemic theory" seeks to draw attention to and provide a framework for the analysis of adverse disease interactions, including their causes and consequences for human life and well-being. Although the majority of this research has focused on HIV, an emerging body of work on syndemics has expanded to other co-occurring conditions.
Syndemic methods: from historical archives to mathematical models.
Methods for evaluating syndemics have been a focus on scholarship for deepening the application of what has largely served as theory to understand why and how social and health conditions cluster together, interact, and are driven by shared forces, from climate (such as escalation of heat, rain, drought, and events) to poverty (such as food insecurity, poor housing, lack of safety, and limited work opportunities). In 2022, Alexander Tsai (an epidemiologist), Emily Mendenhall (a medical anthropologist), and Timothy Newfield (a historian) teamed up on a Special Issue in "Social Science and Medicine" to explore the various methodological ways in which syndemics can be understood, interpreted, and evaluated through history. For instance, historical syndemics may be evaluated using archival data that is incomplete but provides a novel way of thinking about disease biography. This is exemplified by Dylann Atcher Proctor's historical work on gastrointestinal distress in Gabon using historical archives that had never yet been evaluated on their own or synergistically.
Ethnographic data provides a deeper understanding of how and why larger social forces produce disease clusters and interactions and are crucial for understanding "why" syndemics occur. Ethnographic insights have served as the bedrock of syndemic thinking since Merrill Singer's pioneering intellectual and practical work with the concept beginning in the 1990s. His first article based on ethnographic thinking about the SAVA Syndemic came from real time observations as the AIDS epidemic that unfolded in tandem with substance use amidst structural violence in urban America throughout the 1990s and early 2000s. Singer demonstrated how it was impossible to think about one condition without contextualizing the broader social, structural, and health contexts in which people lived. Discussion of ethnographic methods were detailed in Emily Mendenhall's books "Syndemic Suffering" and "Rethinking Diabetes" and is also exemplified in Mac Marshall's book "Drinking Smoke."
The largest body of methodological scholarship has emerged around the utility of epidemiological data. Epidemiological data provides opportunities to investigate the synergistic ways in which diseases emerge and interact with social and health conditions. This latter method has been the focus of contention, particularly in dialogue between Alexander Tsai and Ronald Stall. Early epidemiological studies, for example, evaluated the ways in which social and health conditions co-occurred. Tsai argued that instead, there is a deeper need to interrogate how conditions syngistically interact to cause more adverse health conditions that the conditions would produce on their own. This has led to a slough of emergent research interrogating mathematical models that can take seriously how health conditions may cluster together and interact to affect the health and well-being of populations residing in a specific nation, region, city, or town. A particularly useful model based on the "Soweto Syndemics" study was published in "Nature Human Behavior." In particular, spatial models for thinking through syndemic clusters, such as using GIS, are an emerging area of interest in syndemics research.
Types of disease interaction.
Diseases regularly interact and this interaction influences disease course, expression, severity, transmission, and diffusion. Interaction among diseases may be both indirect (changes caused by one disease that facilitate another through an intermediary) and direct (diseases act in direct tandem).
Iatrogenic.
The term iatrogenesis refers to adverse effects on health caused by medical treatment. This is possible if medical treatment or medical research creates conditions that increase the likelihood that two or more diseases come together in a population. For example, if gene splicing unites two pathogenic agents and the resulting novel organism infects a population. One study suggests the possibility of iatriogenic syndemics. During a randomized, double-blind clinical trial testing the efficacy of the prototype HIV vaccine called V520 there appeared to be an increased risk for HIV infection among the vaccinated participants. Notably, participants immune to the common cold virus adenovirus type 5 had a higher risk of HIV infection. The vaccine was created using a replication-defective version of Ad5 as a carrier, or delivery vector, for three synthetically produced HIV genes. On November 6, 2007, Merck &amp; Co. announced that research had been stopped suspecting the higher rate of HIV infection among individuals in the vaccinated was because the vaccine lowered defenses against HIV.
Examples.
Various syndemics though not always labeled as such have been described in the literature, including:
19th century Native American.
Contact between Native Americans and Europeans during the Columbian Exchange led to lethal syndemics within the Native American population due to diseases introduced which the Native Americans had not encountered before and had not built-up immunity to.
An example of a syndemic from the 19th century can be found on the reservations on which Native Americans were confined with the closing of the U.S. frontier. It is estimated that in 1860 there were well over 10 million bison living on the American Plains. By the early 1880s, the last of the great herds of bison upon which Plains Indian peoples like the Sioux were dependent as a food source were gone. At the same time, after the U.S. military's defeat at the Battle of the Little Bighorn in 1876, there was a concerted effort to beat the Sioux into total submission. Thus, in 1872, Secretary of the Interior Columbus Delano stated: "as they become convinced that they can no longer rely upon the supply of game for their support, they will return to the more reliable source of subsistence [i.e., farming]." As a result, they were forced to give up their struggle for an independent existence on their own lands and take up reservation life at the mercy of government authority. Treaties that were signed with the Sioux in 1868 and 1876 stipulated that they would be provided with government annuities and provisions in payment for sections of their land and with the expectation among federal representatives that the Sioux would become farmers on individually held plots of land. The Sioux found themselves confined on a series of small reservations where they were treated as a conquered people. Moreover, the government reneged on its promises, food was insufficient and of low quality. Black Elk, a noted Sioux folk healer, told his biographer: "There was hunger among my people before I went across the big water [to Europe in 1886], because the Wasichus [whites] did not give us all the food they promised in the Black Hills treaty... But it was worse when I came back [1889]. My people looked pitiful... We could not eat lies and there was nothing we could do." Under extremely stressful conditions, with inadequate diets, and as victims of overt racism on the part of the registration agents appointed to oversee Indian reserves, the Sioux confronted infectious disease from contact with whites. knowledge about the epidemiology of the Sioux from this period is limited, James Mooney, an anthropologist and representative of the Bureau of Indian Affairs sent to investigate a possible Sioux rebellion, described the health situation on the reservation in 1896: "In 1888 their cattle had been diminished by disease. In 1889, their crops were a failure ... Thus followed epidemics of measles, grippe [influenza], and whooping cough Pertussis, in rapid succession and with terrible fatal results..." Similarly, the "Handbook of American Indians" notes, "The least hopeful conditions in this respect prevail among the Dakota [Sioux] and other tribes of the colder northern regions, where pulmonary tuberculosis and scrofula are very common... Other more common diseases, are various forms of, bronchitis ...pneumonia, pleurisy, and measles in the young. Whooping cough is also met with." Indian children were removed to white boarding schools and diagnosed with a wide range of diseases, including tuberculosis, trachoma, measles, smallpox, whooping cough, influenza, and pneumonia.
The Sioux were victims of a syndemic of interacting infectious diseases including the 1889–1890 flu pandemic, inadequate diet, and stressful and extremely disheartening life conditions, including outright brutalization with events like the massacre at Wounded Knee in 1890 and the murder of their leader Sitting Bull. While the official mortality rate on the reservation was between one and two percent, the death rate was probably closer to 10 percent.
Influenza.
There were three influenza pandemics during the 20th century that caused widespread illness, mortality, social disruption, and significant economic losses. These occurred in 1918, 1957, and 1968. In each case, mortality rates were determined primarily by five factors: the number of people who became infected, the virulence of the virus causing the pandemic, the speed of global spread, the underlying features and vulnerabilities of the most affected populations, and the effectiveness and timeliness of the prevention and treatment measures that were implemented.
The 1957 pandemic was caused by the Asian influenza virus (known as the H2N2 strain), a novel influenza variety to which humans had not yet developed immunities. The death toll of the 1957 pandemic is estimated to have been around two million globally, with approximately 70,000 deaths in the United States. A little over a decade later, the comparatively mild Hong Kong influenza pandemic erupted due to the spread of a virus strain (H3N2) that genetically was related to the more deadly form seen in 1957. The pandemic was responsible for about one million deaths around the world, almost 34,000 of which were in the United States. In both of these pandemics, death may not have been due only to the primary viral infection, but also to secondary bacterial infections among influenza patients; in short, they were caused by a viral/bacterial syndemic (but see Chatterjee 2007).
The worst of the 20th-century influenza pandemics was the 1918 pandemic, where between 20 and 40 percent of the world's population became ill and between 40 and 100 million people died. More people died of the so-called Spanish flu (caused by the H1N1 viral strain) pandemic in the single