Can we demarcate epidemiology? A field lost or a field re-invented

One of the most enjoyable and insightful articles I’ve ever read in epidemiology is by Olga Amsterdamska (1953-2009) “Demarcating Epidemiology” (2005) Bringing together a joint historical and epistemological perspective, Amsterdamska explores how epidemiology, a field that in many ways defies demarcation has evolved to understand itself. While I think everyone in epidemiology (and medicine, and everyone actually…) should read this article, I want to highlight some of my favorite parts and put them in context of some other excellent must-reads.

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Amsterdamska, O. (2005). Demarcating epidemiology. Science, technology, & human values, 30(1), 17-51.

Who are we?

‘Who are we?’ is a question that every introduction to epidemiology course grapples with. In “To Advance Epidemiology” Stallones (1980) formulates the ‘theory of epidemiology’ as an axiom and its two corollaries: that “Disease does not distribute randomly in human populations”, but variations occur across time and space, and in response to variations in causal factors. A more vague version of this definition appears in Wikipedia today.

But who are we really? Epidemiologists are well aware that we are not a basic or clinical science, but we rely on the basic sciences and clinical sciences to understand disease processes. We are not a social science, demography, or economics and yet so many our theories and methods dealing with populations and data collection are borrowed from these fields. We’re in a dependent relationship with the field of biostatistics— they could do without us, I’m not sure we could survive without them. We’re neither public health nor in public policy and yet the knowledge we generate finds its way there. Some have pinned this identity crisis on the radical transformation of the field from its inception to its present state.

Traditional versus modern?

Among these, Pearce’s article “Traditional Epidemiology, Modern Epidemiology, and Public Health” (1996) has split epidemiology in two eras: ‘traditional’ versus ‘modern’. The ‘traditional approach’, the epidemiology as practiced by Jon Snow and his contemporaries in mid-19th century, was motivated by public health and studies of populations in situ— focusing on outcomes as a result of “processes and structures”. These ‘traditional’ epidemiological studies tackled structural problems. The tools used were demographic tools, and the outcomes of interest and interventions were almost exclusively at the level of the population. On the other hand, ‘modern epidemiology’, as demarcated by Pearce considers itself a science and embraces reductionist, positivist approaches. Modern epidemiologic studies are often disjointed from a context; subjects are not populations in situ but increasingly individuals—and even organs, DNA, molecules. The ‘gold standard’ from which data is derived is the randomized clinical trial—an experiment—insofar as epidemiologists can conduct a scientific experiment— and the ideal intervention is directed to the individual.

Much like those who lament the invasion of science in humanities (Crimes Against Humanities: Now science wants to invade the liberal arts. Don’t let it happen.”) Pearce warns this has already happened to epidemiology, and perhaps explains the identity crisis we face today. In Pearce’s view, modern epidemiology has morphed into a field which privileges what it views as evidence generated from ‘modern science’, that is modern biomedicine and modern biostatistics, to evidence generated from all other modes of inquiry—including but not limited to science that is now considered passé or too ‘undeveloped’ or irrelevant (“too political”). Pearce makes a compelling case that epidemiology is now dismissing and disregarding the very questions and methods that on which the field was founded—and which only this field can answer. This we are to understand, has emerged only in recent years—a kind of usurpation of scientism, heralded the latest and shiniest methods and approaches, that increasingly marginalized the core of what made epidemiology a distinct field.

Amsterdamska, however, paints a different picture, not one of a field usurped and neutered but one of a field that has re-invented itself again and again to survive.

Engagement or isolation?

Amsterdamska describes epidemiology as a field that has struggled with internal anxieties regarding its involvement with politics and administrative apparatuses and its non-laboratory based, inductive methods since its inception. At the turn of the century, with the advent of the germ theory of disease, society increasingly turned to biomedicine and experimental lab-based sciences to solve problems of health and disease. The biosciences saw great rapid expansion with the founding of National Institutes of Health (NIH) in the US and the Medical Research Council (MRC) in the UK (pg. 39). As ‘the sciences’ increasingly asserted their position in society as ‘epistemic authorities’, some epidemiologists (one notable one being Major Greenwood) may have seen a proverbial writing on the wall for their field: if epidemiology were not to be recognized as a ‘science’ as a field it could be left behind in investigations of disease, and eventually find its demise as a proto-science or mere historic curiosity—a new alchemy.

At the turn of the 20th century, these ‘threats’ translated into effort to demarcate the field and establish its terrain within the broad scope of sciences and create “boundary-work”. The internal anxieties outlined above began to manifest as tension between epidemiology and other emerging fields including biometrics/biostatistics and the biomedical sciences, in particular bacteriology. In biometricians, epidemiologists found adversaries who criticized both the methods of epidemiology and epidemiology-derived public policy and health efforts as lacking “scientific objectivity” (pg. 27). Early epidemiologists such as Arthur Newsholme, viewed this as an attempt of either (1) “usurpation” where biometricians lacking knowledge in disease processes tried to solve problems they didn’t understand using unnecessarily complex mathematical methods (2) “overstepping” by a field that was an “excellent servant but a very bad master” for health investigations . Both these responses reflected an endeavor to demote a competing field as subservient to epidemiology and thereby establish the field’s epistemic dominance.

The internal anxieties also manifested as what Amsterdamska finds persistent attacks on “bacteriologists” and “renegade epidemiologists” (pg. 32). Interestingly Amsterdamska finds no evidence that any active critiques of epidemiology from the quarters of the laboratory sciences ever took place. Nevertheless, epidemiologists such as William Hamer and F.G. Crookshank launched critiques of the field of bacteriology. No surprisingly, early on they also revered adamant opponents of germ theory such as Charles Creighton (Trostle, 1986). Amsterdamska attributes the scathing attacks on bacteriology by British epidemiologists as a ‘scapegoating’ to distract from epidemiology’s own failures, in for example minimizing the public health devastation caused by the 1918 influenza. As well, a pre-emptive act to, once again “limit any potential competition” (pg. 33).

Among these ‘renegade’ epidemiologists who were also subject of critiques, was the epidemiologist and biometrician Major Greenwood, who early in his career was heavily criticized for his statistical work by the community as producing epidemiologic work based on a “mathematical house of cards”  (pg. 28). Later on, Greenwood worked with bacteriologists including W.C.C. Topley and developed experimental epidemiology . This renegade action also earned him criticism from Crookshank who viewed these new methods as comparable to “attendance at cinemas to the study of human life” (pg. 38). Here we find evident a tension between those in the field itself regarding how the boundaries and identity of epidemiology could be asserted. Individuals such as Hamer and Crookshank took an isolationist approach in order to maintain field ‘purity’ and epistemic authority, whereas individuals such as Greenwood and later Wade Hampton Frost saw epistemic authority as being maintain only so long as epidemiology was closely engaging and growing with other sciences on an equal plane (pg. 35).

Cause of death: war or the bullet?

In late 19th century the field of epidemiology was distinguished by the ‘objects’ of its study: disease. Amsterdamska finds that in this early stage, and even with the early advent of germ theory, epidemiologists were not yet concerned with demarcating their field, as the information flowing from bacteriology was found useful and complementary with epidemiologic and public health efforts (pg. 21). During the interwar period epidemiologists began to refine the ‘object’ of their domain, as a specific ‘perspective towards disease’ (specifically infectious diseases) though at least two views on the subject existed (pg. 34).  The subtle difference between these two views was that Greenwood believed a convergent view where all fields were examining the same plane through different perspectives (“bird’s eye view”  of a city, versus a ground tour), whereas Crookshank believed a divergent view where different planes were being examined through different perspectives (“causes of war” versus “individual cause of death in a war”) (pg. 31).

Passage from FG Crookshank. Cited in Krieger, N. (2011). Epidemiology and the people’s health: theory and context. Oxford University Press.

However, the epidemiologic transition to chronic diseases presented a new challenge in that the etiologies and causal links were now complex. The ‘mono-causal’ flat planes of infectious diseases had turned into massive ‘multi-causal’ webs where a ‘single perspective towards disease’ was no longer sufficient. In the challenge posed by chronic diseases the ‘object’ of epidemiology shifted from ‘disease’ to ‘methods’ investigating causal webs associated with health outcomes (pg. 42). One could argue that this transition made epidemiology as a field less defined than ever, as social epidemiologists, environmental epidemiologists etc. emerged whose proximal outcomes of interest often did not directly pertain to a disease process.

However, these methods, often adopted from other fields were used to create a coherent epidemiologic methodological framework, in which rigorous high-quality knowledge could be obtained. Epidemiology now had at its core a methodological framework, from its randomized control trials to the full integration of inferential statistics and hypothesis testing. The complexities of chronic diseases had led to the refinement of methods in the field to better understand multi-causality, including refined study designs and techniques to identify bias and confounding (Hanne, 2007).

The master or the emissary?

The ambition of early epidemiologists had been to establish epistemic authority and be recognized as a branch of science. The transformations that occurred during the transition to chronic diseases in many ways fulfilled this ambition, putting it irrefutably shoulder-to-shoulder with other progenies of the Baconian scientific method. However, it must be asked whether this transformation brings forth Theseus’ paradox: did epidemiology survive its transformation? Furthermore, is the “scientification” of epidemiology—held in such high esteem by the forefather of the field— a good thing?

In contrast to Pearce who lamented the increasing scientism in epidemiology, others fear the exact opposite phenomenon. In “The Rise and Fall of Epidemiology, 1950–2000 A.D.”, one of the foremost thinkers in the field, Kenneth Rothman, forecasted a decline in epidemiology, because it was becoming un-scientific (Rothman, 1981).The article lamented that while the field had made tremendous headways in mid-twentieth century, it would perhaps die in the new century leaving behind only “methods… to serve some future generation with sufficient curiosity to apply them”. The culprits of this inevitable downfall? non-experimental methods (observational studies, ecologic studies), and greater entanglement with governmental bureaucracy. In a way, Rothman’s concerns paralleled that of Major Greenwood and others— in that epidemiology cannot decline into a less ‘scientific’ state lest it be left behind in as a historic relic. This view has been countered by others such as Coleman in “Is epidemiology really dead, anyway?” (2007), have called epidemiology as vital and alive as ever—with observational studies proving a powerful scientific tool, and the field answering new and important questions about the human condition.

Whether it is more scientific or less scientific than it used to be— there is no doubt that epidemiology has transformed— head to head with medicine where from examining disease through descriptive pathology we’ve turned to the lens of prediction. Indeed, increasingly human health is no longer described in terms of symptoms and diagnoses, rather predictive statistics where every individual is at risk—as I once heard it described ‘we’re all sick, we just don’t know it yet.’ In examining these trends, early epidemiologists such as Crookshank, and perhaps even Greenwood who admittedly viewed statistics as “necessary but not sufficient” (pg. 36) , would perhaps find one of their great fears realized: that epidemiology has in fact been usurped by biostatistics and is no longer the master of its own domain, but an emissary linking fields together.

Where do epidemiologists belong?

In its nascent era epidemiologists were clinicians or specialists in other areas often working on behest of governmental institutions. Modern epidemiologists are PhDs trained in the field, and rather than being embedded in health departments they work in institutes of higher education, schools of medicine and/or schools of public health.  Amsterdamska details both the development of identity and work-boundary of epidemiology and the shift of epidemiology in England from the confines of governmental institutions to academic institutions. In summary, associated with changes in the disciplinary identity and boundaries of epidemiology as a field epidemiologist in the UK moved from being embedded within governmental institutions to academic institutions—a trend replicated elsewhere in the world.

As described by Amsterdamska “these changes in the definitions of disciplinary identity of epidemiology went hand in hand with changes in the institutional location of epidemiology, its professional organization, and its practical engagement in public health policy and administration” (pg.19). The construction of boundaries and demarcation of epidemiology, Amsterdamska argues, addressed two challenges faced by the field. First, the ‘real’ and ‘imagined’ challenges posed by fields such as statistics and bacteriology, which created anxiety regarding the encroachment into the domain of epidemiology by these other fields. Second, the methods used by the field, non-experimental and non-laboratory created anxiety regarding its place and relevance in the future of science.

Through demarcation, first of objects and later methods, epidemiologists sought to address the first concern: establish an identity and prevent the encroachment of other fields into their domain. Through, first criticism of shortcomings of other scientific fields’ methods and later incorporation of other field’s methods, epidemiologists sought to address the second concern: asserting the nature epidemiology as a science. It can be argued that the restructuring of identity and the new needs associated with it precipitated into a reactive move to a place that could serve these new needs. For example, academic settings would provide epidemiologists with the opportunity for greater “cooperation and harmonious development” with other academic fields—which Major Greenwood and other interwar epidemiologists conceived of as an immediate need in the discipline (pg. 34). However, it can also be argued that any true shift in disciplinary identity could not occur until there was a proactive move to a place outside the framework, not “stifled” by constraints of the administration and state (p. 41).

It seems that prominent epidemiologists such as Major Greenwood who played an instrumental role in “locating epidemiological research in… academic setting[s]” (p. 40) took a proactive rather than a reactive approach. Their driver for doing so is argued by Amsterdamska to have been two-fold: First, to provide epidemiology with “greater intellectual and institutional autonomy”; second, to permit for opportunities to move beyond the addressing only the practical daily concerns of public health in governance and allow for “the development of epidemiological theory” (p. 40). The association between epidemiology and politics and non-laboratory-based practices is described a “perennial worry” of epidemiologists (pg. 18), and the move outside the governmental apparatus seems to have assuaged these anxieties and provided the opportunity to construct and demarcate their identity.

Foucauldian discourse on power-knowledge and the creation of professional orders provide us with another perspective to view this shift in identity and place. Long before the transitions of the interwar period, epidemiology was already professionalizing as a field, with its own professional society in Britain established in 1850 (pg. 23). Through the Foucauldian lens, professionalization represents a shift in power from the state to the professional order. This is described as a governmentality/professionalism duality, whereby the profession becomes in itself an institution of power, resisting the encroachment of the state and government into its territory, and establishing its own power-knowledge dynamic (Adams, 2012).

Throughout its history epidemiology has been closely associated with public health practice and by extension the state. Foucault’s conceptualization of power-knowledge can be understood as a dynamic in which power and knowledge emerge from one another and reinforce one another. Early epidemiologic knowledge in a large part emerged because it was needed by the state (a monopoly of power); its questions and direction were shaped by the immediate needs of the state. In its early phase, the field is described by Amsterdamska as having been a “tool for monitoring” and “used to underpin the claims that state… should have the jurisdiction to control water quality” among other things (pg. 23). The majority of epidemiologists were not merely associated with the state, rather they worked within the framework of the state – for example in the context of the London General Board of Health responsible for investigating the Cholera epidemics in mid-19th century.

From this perspective, then, the changes in the disciplinary identity of epidemiology and its academic professionalization occurred not to assert epistemic authority not merely in the domain of science, but also to re-center power to the field. As its own institution, epidemiology is subject to its own professional rules (‘methods’ discussed earlier) its own order, norms, and questions of interest. The physical movement into institutions of learning may have been the most practical way to allow for epidemiology to develop as its own independent institution, shifting the power-knowledge dynamic away from the state and into the discipline itself.

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Marzieh Ghiasi (@marziehg), MSc is an MD/PhD epidemiology trainee at Michigan State University. Her current research is focused on the genetic epidemiology of gynecologic disease, focusing on endometriosis. Her background in research is in airborne infectious disease transmission and environmental health. She is passionate about promoting stronger medical education, particularly focusing on epidemiological, biostatistics and clinical research skills.

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