Everyone is now familiar with pandemics and epidemics, but what is a ‘syndemic’? Three decades after the concept was first proposed, Natalie Davies examines whether the syndemic framework can provide a better appreciation for, and ability to address, the disease burden of hepatitis C and injecting drug use.

Understanding the syndemic framework

In the 1990s, Professor in Anthropology Merrill Singer wrote about the constellation of factors that magnified and materially changed the risk of people with substance use problems getting HIV:

“While investigating HIV prevention in drug users, researchers took notice of the constellation of elements that impinged on risk, structural factors such as lack of housing and poverty, and social aspects such as stigma and lack of support systems—all reinforcing the disease burden.”

He noted that factors associated with HIV and substance use – from stigma and poverty, to lack of housing and support systems – “did not merely exist in parallel”; they were intertwined and had a cumulative effect. This became known as the syndemics framework.

A syndemic is … the “combination of co-occurring epidemics and large-scale social forces”.

A ‘syndemic’ is, to put it simply, the “combination of co-occurring epidemics and large-scale social forces”. It indicates the presence of two or more social or structural conditions and diseases that “adversely interact with each other, negatively affecting the mutual course of each disease trajectory, enhancing vulnerability, and which are made more deleterious by experienced inequities”.

Applying the syndemic framework

A 2020 study set in British Columbia (Canada) applied the syndemics approach in an attempt to quantify the burden and distribution of hepatitis C across the population.

The study placed everyone who had been diagnosed with hepatitis C over a 25-year period into six “syndemic risk groups” – each group representing people with different socio-demographic characteristics, as well as other important differences around risk and route of transmission:

  1. Younger people who inject drugs
  2. Older people who inject drugs
  3. Other middle-aged people
  4. People of Asian backgrounds
  5. Rural ‘baby boomers’
  6. Urban, socially-deprived ‘baby boomers’

The largest proportion (40%) of the population who were ‘at risk’ were people who inject drugs. The social and structural vulnerabilities that rendered people who inject drugs particularly vulnerable to, and vulnerable from, hepatitis C included a history of mental health problems, and residing in neighbourhoods with a high level of material deprivation.

Original paper: Syndemic profiles of people living with hepatitis C virus using population-level latent class analysis to optimize health services. By Emilia Clementi and colleagues. Published in the International Journal of Infectious Diseases (2020).

The study delineated between younger people who injected drugs (born after 1965) and older people who injected drugs (born before 1964). Older people who injected drugs had the highest proportion of HIV and hepatitis B co-infections across the six groups. Most also had additional vulnerabilities around drinking problems and liver disease.

For these two age brackets of people who inject drugs, the study indicated that they might need different types of care alongside treatment for their hepatitis C. For example, while both age groups of people who inject drugs were likely to require mental health and substance use services and support from social workers or case managers, the evidence suggested that services for older people who inject drugs might need to include more specialist care because of the presence of hepatitis B and chronic liver disease.

Assessing the utility of the syndemic framework

The six syndemic risk groups in the Canadian study were based on the variable or variables that defined most people in each group or distinguished them from other groups, and were identified using a method called latent class analysis. A major advantage of this approach was that the study could “reveal ‘hidden’ subgroups” in a population of people diagnosed with hepatitis C.

However, slicing the population in this way meant that smaller subpopulations of people at risk of hepatitis C (e.g. people in prison) were not visible. And furthermore, it seems doubtful that the six groups presented would resonate from a policymaking, treatment, or advocacy perspective. The group of ‘rural baby boomers’, for example, was comprised of 32% rural dwellers, 79% baby boomers, 99% heterosexuals, and 0% with HIV. Would it be feasible or desirable to launch a public health campaign or establish a treatment service to meet the needs of this group? These points are worth considering if the syndemic framework is to be operationalised. Otherwise, it risks being limited to a way of describing overlapping social or structural conditions and diseases.

In the UK, resources are often directed towards ‘at-risk groups’ – an approach that, by design, targets risky environments or behaviours. The UK’s National Institute for Health and Care Excellence (NICE), for instance, describes 11 groups at higher risk of contracting hepatitis C. Identifying at-risk groups enables policymakers to target testing and treatment. However, it doesn’t necessarily oblige or result in a holistic response to the overlapping problems or ‘constellation of risk’ that at-risk groups may experience. The syndemic framework, in contrast, treats everything as connected or interconnected, and calls for structural changes. In theory, this means that the syndemic framework could help to address the root causes of hepatitis C in a way that responding to single-category at-risk groups might not. But ultimately, the way that syndemic risk groups are defined will have a large bearing on whether the syndemic framework can be useful in practice.

by Natalie Davies

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