Introduction to Social Epidemiology

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Introduction to Social Epidemiology

• Illustration via a case studyType 2 Diabetes

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The prevalence of diabetes varies widely among
people, apparently both according to race and
living circumstances

• People of European origin
• In Britain 2
• Germany 2
• Australia 8
• USA 8
• Native Americans
• Chilean Mapuche 1
• US Hispanic 17
• US Pima 50

• People in New Guinea
• Rural 0
• Urban 37
• Aboriginal Australians
• Traditional 0
• Westernized 23
• Black Africans
• Rural Tanzania 1
• Urban S. Africa 8
• United States 13

WHY?
Source Jared Diamond. Nature 2003423599
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Type 2 non-insulin dependent diabetes

• Etiologically heterogeneous common feature is
  high blood glucose due to altered insulin
  secretion and insulin resistance
• Patients still produce insulin but are unable to
  respond effectively to it
• Patients are typically obese
• Often a disease of socioeconomic disadvantage.

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Genes and Diabetes

• Several genes implicated presumably these must
  have conferred a survival advantage at some time
• For example, the hypothesized thrifty gene
  enables a person carrying it to use food
  efficiently in times of plenty in preparation for
  famine conditions. (JV Neel. Am J Human Genet
  196214353-362)
• Perhaps this may be relevant to diabetes?

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Genes interacting with lifestyle?

• Diabetes involves genetic factors and lifestyle,
  especially diet
• Symptoms disappear under conditions of starvation
  (e.g., siege of Paris, 1870)
• Migrant populations see increases (immigrants to
  Israel Japanese moving to USA) perhaps their
  diet changes when they migrate?
• Rates fluctuate with economic conditions
• Lifestyle disorder seen in genetically
  susceptible populations environmental factors
  associated with lifestyle unmask the disease.

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The counter-arguments

• 30 years of searching have not identified a
  culprit gene
• Obesity and NIDDM are responses to late 20th
  century lifestyles, so its really a
  social-environmental issue
• There is also a rival hypothesis of intra-uterine
  exposure to hyperglycemia that has been supported
  in cohort studies
• Or, alternatively, hypothesis of early childhood
  under-nutrition (see McDermott, Soc Sci Med
  1998471189-95)

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Some remaining questions

• Explanations are not merely scientific they lead
  to blame and action. Do we blame individuals for
  their unhealthy diet, or do we blame their
  cultural heritage, or capitalism for its
  marketing practices, or governments, or
  scientists, or ?
• Will advances in bench science remove the need to
  worry about the social context of illness?
• What are the social implications of the current
  emphasis on searching for genetic explanations?
• More broadly, are the causes of individual cases
  the same as the causes of incidence rates?
  (I.e., is it the same factor that explains why
  one individual is diabetic, that also explains
  racial differences?)
• So, should we view a population as just an
  aggregation of individuals, or is it somehow
  different?

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Ways of thinking about disease
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Sussers Eras in Epidemiology
Source M. Susser. Am J Public Health
199686674-7.
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Life-course human development view

• Health is a consequence of multiple deficits
• Health is an interaction between living context
  and bio-behavioral regulatory systems
• Personal health trajectories reflect the effect
  of many risks these cumulate over time
• The timing and sequence of the events is
  important there are periods of enhanced
  susceptibility
• E.g., the weathering hypothesis cumulative
  exposure to stressors leads to vulnerability

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Things the social epidemiologist typically
worries about

• Biological determinism, represented in the human
  genome project perception that we are largely
  controlled by our genes
• Social Darwinism sociobiology
• Implicit reductionistic deterministic stance
  narrow focus on pathogenesis
• Treatment or early detection rather than
  primordial prevention
• Denial of the agency of people and communities

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Reactions to uncertainty

• There is much we do not understand. DL Weed
  (1988) described three reactions to scientific
  uncertainty
• Belief (retreat to commitment). Implies
  cessation of enquiry. Characteristic of the
  religious right
• Statistics and reference to probability. This
  does not help us decide where to look for further
  evidence, or what to ignore, nor when we have
  arrived
• Criticism. Will not make us certain, but helps
  to bring weaknesses to the surface
• Fourth way may be to integrate disciplines how
  do we do this?

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Conceptual Model for Social Epidemiology
Starting Point Inequalities in Health
Explanations Causal Theory
Designing Multiple Interventions
?
?
Sociological Explanations
Biological Processes Overall Model
Biological
Societal Processes
?
Life Events
PNI
Social Support
Coping, Vulnerability Resistance
Individual
?
Work
Stress Theories
?
Behavioral Theories
Personality