Modern Theories of Disease

1. Modern Theories of Disease
Mohammad Aslam Shaiekh
MPH – 3rd Batch
School of Health and Allied Sciences (SHAS)
Pokhara University (P.U)
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2. Contents
• Article in a short glance
• Theory of disease (from personal perspective)
• Authors point of views (from article
perspective)
• Conclusion
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3. Article in a short glance
• Title: Theories for social epidemiology in the
21st century: an ecosocial perspective
• Authors: Nancy Krieger
• Journal: International journal of Epidemiology
• Volume: 2001; 30
• Page number: 668-677
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4. Germ theory of disease
• In 1860, Louis Pasteur demonstrated the
presence of bacteria in air.
• The theory emphasized that the sole cause of
disease is microbes.
• The theory referred to as one to one
relationship between disease agent and
disease.
• Disease agent Man Disease
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5. Epidemiological Triad
Environment
Agent Host
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6. Multifactorial causation
• The germ theory of disease overshadowed
the multiple cause theory in late 19th
century.
• As a result of advancement in public health
communicable disease began to decline and
are replaced by new type of disease so
called modern disease of civilization.
• Example: lung cancer, CHD, Mental illness,
chronic bronchitis etc.
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7. Web of disease causation
• The model of disease causation was suggested by
Mac Mahan and Pugh.
• This model is ideally suited in the study of
chronic disease is not known but is the out come
of interaction of multiple factors.
• Consider all the predisposing factors of any type
and their complex interaction with each other.
• This theory does not imply that the disease
cannot be controlled unless all the multiple
causes or chain of causation or at least a number
of them are appropriately controlled .7/6/2018 Aslam Aman_MPH 7

8. Web of causation for myocardial infarction
Change in lifestyle
Abundance
of food
Obesity
Lack of
Physical
exercise
Smoking
Stress
Hypertension
Emotional
disturbances Ageing and
other factors
Hyperlipidaemia
Increased catacholamines
thrombotic tendency
Coronary
atherosclerosis
Changes in walls of arteries
Coronary occlusion
Myocardial ischaemia
Myocardial infarction
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9. Socio-environmental model
• Not so much concerned with the causes
of disease, rather it focuses to identify the
main factors that make and keep people
healthy.
• Composed of four major categories of
factors: human biology, lifestyle,
environment and health system. All these
factors influence health status positively
or negatively.
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10. Current theoretical trend in social
Epidemiology (From Articles)
1. Psychosocial theory
2. Social production of disease and/or political
economy of health
3. Ecosocial theory and related multilevel
dynamic framework
I. Ecosocial theory
II. Eco-epidemiology
III. Social ecological system perspective
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11. Psychosocial theory
• As is typically the case with scientific theories.
first articulated in the 1920s and refined in the
1950s as epidemiologists increasingly study
cancer and cardiovascular disease.
• its genesis can be traced to problems prior
paradigms could not explain, in this case,
why it is that not all people exposed to
germs become infected and not all infected
people develop disease.
• social environment’ comprised of psychosocial
factors generated by human interaction.
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12. • The model becomes increasingly diffuse and,
by 1960, ‘web of causation’ is born.
• The importance of the ‘host-agent-environment’
model for psychosocial epidemiology is proved by
the title of one of the field’s still-defining papers:
John Cassel’s final opus, ‘The contribution of the
social environment to host resistance’.
• This article expands upon frameworks elaborated in
the 1940s and 1950s linking vulnerability to
disease to both physical and psychological
stress.
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13. • Cassel’s central hypothesis is that the ‘social
environment’ alters host susceptibility by
affecting neuro-endocrine function
• His list of relevant psychosocial factors
includes: dominance hierarchies, social
disorganization and rapid social change,
marginal status in society, including social
isolation.
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14. • Cassel ultimately concludes that the most
‘feasible’ interventions to reduce disease will
be ‘to improve and strengthen the social
supports rather than reduce the exposure to
stressors’.
• One is ‘allostasis’(repeated exposure to
chronic stressful environment), introduced as
an alternative to ‘homeostasis’ in 1988 by
Peter Sterling and Joseph Eyer to describe
systems that achieve balance through change
that protect the body by internal and external
stress
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15. Social production of disease and/or
political economy of health
• Looking back at social analyses of health of the
1830s and 1840s, as well as 1930s and 1940s,
this school of thought—emerging in the politically
unstable 1960s and 1970s—focuses on what it terms
the ‘social production of disease’ and/or ‘political
economy of health’.
• By 1979, the trend’s broad theoretical contours are
encapsulated in two books: The Political Economy
of Health, by Lesley Doyal, a British health policy
analyst, and Epidemiologia Economia Medicina y
Politica, by Jamie Breilh, an Ecuadorian
epidemiologist.7/6/2018 Aslam Aman_MPH 15

16. • Within this trend, initial conceptual and empirical
analyses chiefly focus on class inequalities in health
within and between countries.
• social inequalities involving race/ethnicity, gender
and sexuality, as they play out within and across
socioeconomic position, within and across diverse
societies.
• Health impacts of rising income inequality, of
structural adjustment programs imposed by the
International Monetary Fund and the World Bank, of
neoliberal economic policies favoring dismantling of
the welfare state, or of free- trade agreements
imposed by the World Trade Organization.
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17. Implications
1. Vision of social justice.
2. Absent concerns about social equity, economic
growth and public health interventions may end
up increasing, not decreasing social inequalities in
health if the economic growth increases economic
inequality.
3. Greater familiarity with the emerging field of health
and human rights.
4. Social epidemiologists must be key actors in
ensuring occurrence of the vital public health
activity of monitoring social inequalities in health.
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18. Ecosocial theory
• This theory was introduced in 1994 which
systematically links social and biological
processes.
• It is a broad and complex theory with the purpose
of describing and explaining causal relationships
in disease distribution.
• The theory is also suited to analyze the
relationships between social factors and disease
development in public health research.
• Focuses on spiderless two-dimensional ‘web of
causation’.
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19. Eco-epidemiology
• It was introduced in 1996 by Mervyn Susser.
• Referring to nested ‘interactive systems’, each
with its localized structures and
relationships.
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20. Social ecological system perspective
• The ‘social-ecological systems perspective’
invoked by Anthony McMichael in 1999,
depicting a cube, representing the ‘present/past’,
whose three axes extend from individual-to-
population, proximate-to-distal, static/modular to
life course and which is projected forward, to
‘future’.
• Focuses on current and changing population
pattern of health, disease and well-being in
relation to each level of biological, ecological and
social organization.
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21. Dynamic Perspective
• Embodiment means the way of incorporating
biologically with the external environment that
we live in.
• Pathways of embodiment refer to the paths
through which embodiment is made possible.
• Cumulative interplay between exposure,
susceptibility and resistance.
• Accountability and agency.
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22. Conclusion
• Ultimately, it means whether any of the
three theoretical frameworks discussed in
this article—psychosocial, social production
of disease/political economy of health, and
emerging ecosocial and other multi-level
frameworks—are best suited for guiding
social epidemiological research in the 21st
century.
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23. • To generate the data required to test and refine
our theoretical frameworks, prioritization
should be on: enhanced monitoring of social
inequalities of health, so that data are
available—cross-stratified—by class, gender,
and race/ethnicity and any other social groups
subject to economic and social discrimination,
to gauge progress and setbacks in reducing
social inequalities in health, funding
interdisciplinary aetiological research to identify
conjoint social and biological determinants of
disease.
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24. Thank you !
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