Theoretical, ethical, contextual,
practical and critical foundations
for future epidemiology
Raj Bhopal,
Bruce and John Usher Professor of Public Health,
Public Health Sciences Section,
Division of Community Health Sciences,
University of Edinburgh, Edinburgh EH89AG
Raj.Bhopal@ed.ac.uk
Educational objectives
On completion of your studies you should
understand that
 Theory, method and application are
interrelated.
 Epidemiology serves the community in a
number of ways, but predominantly through its
role as one of the underpinning sciences of
public health and medicine.
 Ongoing vigorous debate on the future of
epidemiology probably heralds a paradigm
shift.
 Epidemiology is both broadening and
specialising.
 The context in which epidemiology is learned
and practised is important in determining its
nature.
The interrelationship of theory, methods
and application: a question of values
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Epidemiology has entered the 21st century with
both its exponents and critics questioning its
foundations, record and future.
Epidemiology has been accused of:
being atheoretical;
divorced from its source of problems, theories
and applications (public health);
the source of spurious, confusing and
misleading findings;
over-dependent on the ‘black box’ risk factor
approach;
and
irrelevant in resolving some major problems,
e.g. the growing consumption of illegal drugs, the
rising prevalence of smoking in developing
countries and health inequalities.
Underlying philosophy of
epidemiology
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The philosophy and theory underpinning
epidemiology, as in most other disciplines, is
seldom explicit.
Philosophically, epidemiology takes a
positivist stance.
Problems can be solved through data which
are usually, but not always, quantitative.
However, advances may follow inspiration and
insights that are not based on quantitative
data.
Future epidemiology is likely to involve closer
ties between qualitative and quantitative
approaches.
The fundamental epidemiological question is
why differences in disease prevalence and
Exercise: fundamental
influences on health
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List 5 or 6 broad and fundamental
influences on health and disease, i.e.
those influences that change the
population patterns of disease.
Fundamental influences
generating disease patterns
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Changes in the physical, chemical and
radiation environment.
Genetic evolution of microbes, animals
and humans.
interaction between humans, microbes
and animals.
Human social and economic
circumstances
Cultures and behaviours.
Human inventions and discoveries
Figure 10.1
Natural
environmental
change
Human
interventions,
discoveries and
manipulations of
the environment
Changes leading to
altered interaction
between microbes,
animals, and plants
Social change in human
populations - in material
circumstances, and
behavior
Influence on
individuals and
families
- varies by place
Genetic changes in
microbes, plants,
animals and humans
The
phenomena
underlying
population
variations
Over time population differences host, agent or
environment factors
Population variations in health and disease patterns
Demonstrate population differences in disease rates by time,
place and person/population
Analysis and interpretation of differences to gain insight into
the evolution of these patterns, and hence the causes
Use information to improve health
Epidemiology
tries to
understand
above
phenomena
Uses of epidemiology
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Morris, in his classic book, “Uses of
Epidemiology” published in 1957, portrayed
epidemiology as a discipline with multiple
applications.
In most contemporary textbooks, by
comparison, the vision of epidemiology is
narrower, and probably narrowing.
Question under current debate is whether
epidemiology is primarily an applied discipline
or primarily a science where methods,
technique and theory dominate.
I think it is an applied discipline where
methods, technique and theory are very
important
Interdependence of application,
theory and methods
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To illustrate how theory, method
application are interdependent I have
chosen two topics of personal interest:
setting priorities in health care and
assessing the impact on health of local
polluting industries.
Setting priorities in health and
health care
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Priority setting within health and health
care mixes science and politics.
Epidemiological data on disease frequency,
patterns, causes, risk factors and
effectiveness can feed the debate
Theories on causation, and predictions of the
changing size of the problem, are central to
prioritising.
Understanding of causation is complementary
to descriptive data on the burden of disease.
Needs of policy and practice have provided the
stimulus for modes of analysis (PYLL,
attributable risk, NNT etc) that are not essential
to causal epidemiology.
Teesside study of environment
and health
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Heavy industry is vital but there is a price
to pay - pollution.
Industries are facing complaints, adverse
publicity, litigation and public inquiries.
Our study of the impact of petrochemical
and steel industries on the health of
people in Teeside typifies applied public
health.
Teesside study of
environment and health
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First step was for us to devise the theoretical
framework within which the problem is to be
resolved.
Positivist approach based on hypotheses,
epidemiological study design, data collection
and an understanding on how the data would
be interpreted.
If a disease or health problem was causally
related to living close to industry, then there
would be a gradient with distance of residence,
those closest having the highest rates, those
furthest the lowest.
Teesside study of
environment and health
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Underlying theory of health and disease was that
long-term exposure to low levels of industrial air
pollution does harm, rather than good.
Causal thinking was based on the
epidemiological criteria (guidelines) for causality.
Outwardly atheoretical, pragmatic, public health
orientated projects may be founded on important
epidemiological theories and concepts.
Readers who do not share these theories and
concepts, and who are either not familiar with or
confident about the methods, will not be
comfortable with the results.
However, these were not made explicit at all
before, during or after publication of the Teesside
study, but after much reflection.
Four components of a paradigm,
or a disciplinary matrix as
identified by Kuhn
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Symbolic generalisations e.g. The laws of
physics as given in mathematical formulae.
Beliefs in particular models e.g. heat as a
kinetic energy.
Values e.g. the key goal of science being
accurate predictions.
Exemplars i.e. classic examples of problems
and their solutions, upon which Kuhn places
especial emphasis.
Paradigms: the evolution of
epidemiology
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In this essay, ‘normal science’ means research
firmly based upon one or more past scientific
achievements, achievements that some
particular scientific community acknowledges
for a time as supplying the foundation for its
further practice. Thomas Kuhn. The Structure
of Scientific Revolutions
In 1996 Susser and Susser called for a
paradigm shift in epidemiology.
To call for a new paradigm is a severe
provocation for it declares the current
paradigm inadequate.
Vigorous debate and resistance to change are
identified by Kuhn as precursors to change.
Four paradigms in epidemiology
identified by the Sussers
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Exploratory description of disease (e.g. Graunt's
analysis of the London Bills of Mortality in 1662:
and Ramazzini and occupational exposures,
1700). In this period there was a change from
sickness being seen as a result of disease
entities not as humoral imbalance.
Miasma theory of disease - the idea that disease
arose from foul emanations from pollution (18th
Century).
Germ theory of disease (19th Century).
Multiple causes as captured in the black box
metaphor (20th Century).
Exercise: waning of diseases
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Reflect on the diseases that
contemporary doctors either do not,
or extremely rarely, see.
Now, reflect on diseases that may
not be seen by doctors in 100 years
time.
Waning of diseases
Physicians in 100 years time may not see
 mesothelioma (a cancer resulting from
asbestos),
 tuberculosis, polio, measles, guinea
worm.
 stroke and heart disease.
 AIDS
How has epidemiology adapted to cope with
such changes?
Scope of epidemiology and
specialisation
Epidemiology has broadened and specialised
 Subdivisions of epidemiology
 Infectious disease epidemiology
 Chronic disease epidemiology
 Health care epidemiology
 Public health epidemiology
 Social epidemiology
 Clinical epidemiology
 Genetic epidemiology
 The benefits are those of all forms of specialisation.
 Costs of specialisation are fragmentation of the
discipline.
 The scope for specialisation is reliant upon context
The context of epidemiological
practice in the USA and UK
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The vision of public health problems has
become more scientific with issues of theory,
measurement and method receiving close
attention, so academic and service public health
goals have diverged.
U.S. School of Public Health environment is large
enough to offer a career path within this system
for professional researchers.
Professional epidemiologists set up and sustain
organisations such as the Society for
Epidemiological Research and the American
College of Epidemiology.
Question for epidemiologists in such settings is
this - what is the role of epidemiology in such
partnerships for public health?
The context of epidemiological
practice in the USA and UK
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Epidemiologists in Britain, perceive
themselves first as statisticians, physicians,
public health specialists or social scientists.
Work in multidisciplinary departments.
Question for epidemiologists working in such
settings is - what is the role of epidemiology in
the world of science, and how is theoretical
and methodological work to be nurtured?
The practice of epidemiology
in public health
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Epidemiology is a key science that underpins
public health and increasingly clinical practice
too.
Epidemiological textbooks usually proclaim
the applications of epidemiology, as the
foundation science of public health, but most
focus on design and methods for causal
research.
A role as an applied science imposes on
epidemiology the need for a code of ethics and
good conduct.
Ethical basis and proper conduct of
epidemiology: the need for a code
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Three issues of interest to me.
Manipulation of scientists by the
tobacco industry.
Manipulation of authorship.
Research on ethnicity and race.
Tobacco and health
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Industry has manipulated research into
tobacco and health.
Fostering controversy.
Countering authoritative review articles
through an international network of paid
scientific ‘consultants’.
Concealed or distorted evidence from its own
research showing the addictive and harmful
nature of smoking.
Epidemiologists need to be armed with an
ethnical code to guide them in making the right
decisions.
Authorship
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Authorship of scientific papers is increasingly
important.
View that only work that has passed the scrutiny of
peers is reliable and trustworthy (a concept itself
worthy of scrutiny).
Key factor in promotion.
Academic appointment.
Service appointments, promotion and distinction
awards.
Winning research grants.
Finances coming into Universities.
Tempting individuals to accept authorship on papers
to which they have not contributed sufficiently.
Allocation of authorship is complex and raises
ethical issues central to scientific integrity.
The International Committee of Medical
Journal Editors' criteria for authorship
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An “author” is generally considered to be
someone who has made substantive intellectual
contributions to a published study, and
biomedical authorship continues to have
important academic, social, and financial
implications
Authorship credit should be based on 1)
substantial contributions to conception and
design, or acquisition of data, or analysis and
interpretation of data; 2) drafting the article or
revising it critically for important intellectual
content; and 3) final approval of the version to be
published.
Authors should meet conditions 1, 2, and 3.
Ethnicity and race
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Ethnicity and race are among the top five or
so most important variables in epidemiology.
Hippocrates contrasted the feebleness of the
Asiatic races to the hardiness of the Europeans.
Concept of race was of human groups shaped by
their ancestry in different environments
especially climate.
Idea of races as distinct species, which was long
and seriously debated, gave way to races as
biological subspecies.
Differences among races were usually assumed
to be biological, interpreted to show superiority
of white races and used to justify policies which
subordinated “coloured” groups.
A perception of inferiority in relation to health can
be fostered by research focusing on problems
more common in minority ethnic groups, and, by
Ethnicity and race
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When research implies genetic factors rather
than environmental ones ethnic minority
groups may be perceived as biologically weaker.
Science that indicated such weakness helped
justify slavery, social inequality, eugenics,
immigration control, and racist practice of
medicine.
Studies of ethnic and racial variations in disease
pose a challenge to the maintenance of high
ethical standards in epidemiology.
Racial prejudice is fuelled by research portraying
ethnic minorities as different, usually inferior to
the majority.
Race and ethnicity are epidemiological variables
that show the importance of historical, political
and social awareness among epidemiologists.
Ethical guidelines
In 1998, the International Epidemiology
Association’s European Group published a
code of practice for epidemiologists which
states that epidemiologists should:
 Seek the truth in good faith without doing
harm or jeopardising personal integrity.
 Judge their own work and ideas and those of
colleagues in an impartial manner.
 Disclose conflicts of interest to ethical review
committees.
 Publicly acknowledge all research
sponsorship.
 Publish all research with scientific merit.
 Refuse requests to withhold findings, change
or tone down the content of reports, or delay
publication unreasonably.
Critical appraisal in
epidemiology: separating fact
from error and fallacy
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Critical appraisal is important because much
of what we know as the truth is wrong sometimes dangerously so.
Reflect on some medical and public health
activities which were widely practised but are
now known to be wrong, some dangerously
so.
Your reflection should include both historical
activities, say, before the turn of the twentieth
century and more recent ones.
Now, reflect on some current policies and
practices that may meet the same fate.
Critical appraisal: follies and fallacies
in medicine
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Critical appraisal is the use of the ‘scalpel of
scepticism’ to extract truth from error in research.
Petr Skrabanek and James McCormick’s book
Follies and Fallacies in Medicine is a gold mine of
examples.
The fallacy of association being causal
The Weight of Evidence Fallacy
The fallacy of repeated citation
Fallacy of Authority
Fallacy of Simple Explanation
The Fallacy of Risk
The Fallacy of Inappropriate Extrapolation
The Fallacy of Significance Tests
The Fallacy of Obfuscation
Fallacy of Covert Bias
The nature of critical appraisal
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Critical appraisal is not just about criticism.
As in a book, film or theatre review you assess
how good the work is in relation to
expectations and what has gone before.
Austin Bradford Hill posed four simple
questions to guide the reading of scientific
papers:
- Why did the authors start?
- What did they do?
- What did they find?
- What does it mean?
Critical appraisal:
epidemiological questions
The questions below can help to produce a
critical appraisal specific to epidemiological
research.
 Is an epidemiological approach appropriate to
the problem under study? What alternative
methods would also help resolve the problem?
 What is the study design and is it suitable for
the problem addressed?
 Are the dates on which the sampling frame
was compiled given?
 Is the date or time period over which data were
collected given?
Critical appraisal:
epidemiological questions
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Have terms/labels used to describe
populations or sub-populations been defined
and justified?
Is the study sample representative of a larger
population, and hence, are the results likely to
be more widely generalisable?
Are the sampling and measurement methods
equivalent in the groups to be compared?
Are compared populations or subgroups
similar on key variables?
If not, are the differences sufficiently small to
permit adjustment using a weighting technique
such as age standardisation, or other
statistical techniques such as logistic
regression?
Continuing education: role of
historical landmarks
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Role of the classics, or in Kuhn’s terminology,
exemplars for contemporary work.
Lind investigated scurvy and reported his
findings in 1753
The story of the prevention of scurvy by eating
citrus fruits shows (a) that putting research into
practice is a long-term endeavour. (b)
mechanistic understanding, though valuable, is
not crucial to put epidemiology into public health
practice
The story of Edward Jenner’s vaccination against
smallpox shows the need to (a) listen to the
public with an open mind (b) test a hypothesis
with experiment (c) those making a discovery
need to be champions of its dissemination and
implementation.
Continuing education: role of
historical landmarks-John Snow
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Classic investigation by John Snow of cholera
also illustrates important principles.
Miasma theory was favoured.
Snow studied what he described as ‘the most
terrible outbreak of cholera which ever
occurred in this kingdom’- the epidemic of
cholera in Broad Street, Soho (1854).
Suspected some contamination of the water in
the Broad Street pump.
The dead lived or worked near the pump.
Nearby workhouse and brewery had their own
water supply and little cholera.
People living far away but drinking Broad
Street pump water were afflicted.
Continuing education: role of
historical landmarks-John Snow
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Water, not miasma in the air, he concluded, is
the source of the morbid matter that causes
cholera.
He published in 1849 and 1855, and gave
evidence to many learned committees.
Was unable to convince those in power and
died in 1858 before his ideas were accepted.
Snow’s book cost him two hundred pounds to
publish and he sold 56 copies in three years,
making three pounds, 12 shillings.
Reflection on the future of
epidemiology
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In industrialised countries the challenges for
epidemiology will, increasingly, lie in the
prevention and control of the diseases of older
people.
Solutions to these problems of old age may lie
in improving maternal, foetal and infant health.
Relative poverty in early life, and wealth in
later life, may be the basis of maladaptation,
triggering diseases such as coronary heart
disease and diabetes.
In many developing countries problems of
poverty (inadequate sanitation, inadequate
nutrition and communicable disease) are
combining with those of the post-industrial era
(cancer, heart disease, stroke and road traffic
accidents).
Reflection on the future of
epidemiology
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Economic and health inequalities will hold
centre stage in public health
The injustice of gross waste in some
countries, and horrendous poverty in others
will be increasingly unacceptable.
Epidemiology and Public Health will face
ethical and a technical challenges.
One key question facing epidemiology is
whether it should be an advocate for
eradication of public health problems or a
dispassionate contributor of science.
Epidemiology will need to provide insights into
complex mechanisms e.g. those by which
wealth and health interact.
Reflection on the future of
epidemiology
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Human genome mapping project will re-ignite the
question of the relative importance of genetic and
environmental factors even although the
environment-gene interaction is all-important
Some principles will help to guide
epidemiologists in the coming whirlwind of
research
The genetic pool changes slowly and genetic
variations between populations are small
The environment changes rapidly, and differs
greatly from place to place.
Occurrence of most common diseases shows
massive geographical and time period variation
Changes point to the dominance of
environmental causes.
Reflection on the future of
epidemiology
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Genetic factors provide the stage in the
great drama of disease causation, but the
environment is the leading player.
advances in genetics will undoubtedly
impact on the diagnosis and management
of disease
in the future epidemiologists will need to
be trained in genetics.
Reflection on the future of
epidemiology
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Molecular science will deepen understanding.
Yet, the public health dividend will come from
altering the pattern of risk factors in the whole
population.
Not simply biochemistry that determines an
individual and population’s serum cholesterol
level but how food is grown, processed,
purchased, cooked and eaten.
Behaviours, including dietary ones, are not
just personal taste, but affected by,
Trade agreements, agricultural policy,
marketing, economic subsidy as determinants
of costs, availability and consumption.
Reflection on the future of epidemiology
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Epidemiologists will need to work harder to
understand how diseases are generated through
the interactions that people make when living in
groups.
How societies work and can be changed to
promote health.
Development of such understanding will come
faster and better in multidisciplinary environments.
Epidemiology will become a vital area of
knowledge for all clinical and public health
researchers and practitioners.
Epidemiology will help them envision the causes of
ill-health and to develop coherent policies, laws,
and health care systems to generate health from
the pattern of disease.
Summary
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Theory underpinning epidemiology is seldom
made explicit.
Epidemiology takes a positivist stance.
The basic theory is that systematic variations
are a product of differences in the prevalence
of, or susceptibility to, the causal factors.
Epidemiological methods quantify variations in
disease patterns and their causes, to establish
associations, and to test resultant hypotheses
on causes.
A vigorous ongoing debate on the future of
epidemiology indicates that major changes are
coming.
Summary
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Rise of genetic epidemiology.
Social epidemiology.
Epidemiology as a prime force in public health.
Need for a code of ethics.
Critical evaluation of research as a crucial
skill.
Attention both to technical excellence of
epidemiology, and to its value in the historical,
political, social, and geographical context.
Epidemiologists to have an understanding of
the wide determinants of health and disease.
Achieved by broad studies of the history and
achievement of the key disciplines
contributing to epidemiology.
Keen interest in contemporary debates and
future trends.