PH2610 Introduction

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PH2610 Introduction

• August 26, 2002
• Lowell E. Sever, Ph.D.

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Outline of Topics

• Course personnel procedures
• Getting to know you
• What is Epi demi ology?
• What is health?
• Doing epidemiology thinking epidemiologically
• Using epidemiology and the core public health
  functions

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The Territory of Epidemiology (Stallones 1980)
Organs
Societies
Molecular and submolecular particles
Cells
Individuals
Families
Communities
Epidemiology
Clinical Research
Pathology, Physiology
Cell Biology
Molecular Biology
The Biomedical sciences arrayed on a scale of
biological organization
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THE RELATIONSHIP BETWEENEPIDEMIOLOGY
CLINICAL MEDICINE
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Outline of Topics

• A very brief glimpse at some epidemiological
  history
• Concepts of disease causation
• Counting bodies John Graunt and the London
  Bills of Mortality
• Cholera and water Who was John Snow and why is
  there a pub named after him?

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Historical Glimpses

• Concepts of disease causation
• 5th Century B.C. The role of the physical
  environment and disease (Hippocrates - Airs,
  Waters and Places)
• 17th Century Quantification of disease patterns
  in London
• 19th Century John Snow and cholera epidemics in
  London

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Historical development of theories of disease
causation

• Divine retribution
• Evil spirits
• Imbalance in body humors caused by air, water,
  land, stars
• Spontaneous generation

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Historical development of theories of disease
causation

• Miasma Disease transmitted by miasm or cloud
  clinging to earths surface
• Germ theory of disease and Henle-Koch postulates
  The most important postulate is that the
  microorganism must always be found with the
  disease. This embodies the idea of specificity
  of cause, i.e., a one-to-one relationship between
  an exposure and disease.

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Historical development of theories of disease
causation

• Ecological model of disease Disease results
  from the interaction of factors related to the
  host, the agent, and the environment.

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Historical development of theories of disease
causation

• Web of causation A paradigm for the causes of
  chronic diseases. Important shift from the
  Henle-Koch postulates and the ecological model is
  the idea of multiple causes.
• Recent controversies
• Causation cannot be established (Philosophical)
• Causal criteria should be abandoned (Not really
  criteria but guidelines for interpretation of
  empiric information)
• Has anyone seen the spider that produced the web?

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Public Health

• The Discipline of Compassion

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Two Main Goals of Public Health

• Optimize population health by applying scientific
  knowledge.
• Decrease population health disparities by
  ensuring equal access to health services.

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Epidemiology and Biometry are the public health
disciplines that scientifically wipe away the
tears of human misery. David Smith, M.D. Former
Texas State Commissioner of Health
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Introduction

• Defining epidemiology
• The nature of epidemiology
• Assumptions underlying epidemiology
• Changing paradigms changing definitions
• Studying states of health disease, illness and
  sickness and the WHO definition of health
• Who (person)
• When (time)
• Where (place)

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Approaches to Epidemiology

• Learning to do epidemiology
• Epidemiology as a science
• Learning to think epidemiologically
• Epidemiology as a core discipline in the practice
  of public health

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Epidemiology A Classic Definition

• Epidemiology is the study of the distribution
  and determinants of disease frequency in human
  populations.
• (MacMahon and Pugh, 1970)

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Epidemiology

• Epidemiology is the study of the distribution
  and determinants of disease frequency in human
  populations

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Stallones Axiom of Epidemiology

• Disease does not distribute randomly in human
  populations
• Corollary 1 Nonrandom aggregations of human
  disease are manifested along axes of measurement
  of time, of space, of individual personal
  characteristics, and of certain community
  characteristics.

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Stallones Axiom of Epidemiology

• Disease does not distribute randomly in human
  populations
• Corollary 2 Variations in the frequency of human
  disease occur in response to variations in the
  intensity of exposure to etiologic agents or
  other more remote causes, or to variations in the
  susceptibility of individuals to the operation of
  those causes

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Aims of Epidemiology

• Describe
• Explain
• Predict
• Prevent

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Overview of Epidemiology

• Disease distribution
• What?
• Who?
• When?
• Where?
• Disease frequency
• count cases
• need a systematic approach
• need records

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Overview of Epidemiology

• Epidemiologic research assumes
• Variation in health status and disease
  occurrence is found among both individuals and
  populations
• Disease occurrence is not random
• Systematic investigation of different populations
  can identify causal (risk) and preventive
  (protective) factors

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Overview of Epidemiology

• Distribution Frequency
• Hypotheses
• Determinants

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Overview of Epidemiology

• The bottom line
• Clues from many sources Form hypothesis
• Conduct epidemiologic study Test hypothesis

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Epidemiology

• Epidemiology at any given time is something more
  than the total of its established facts. It
  includes their orderly arrangement into chains of
  inference which extend more or less beyond the
  bounds of direct observation. Such of these
  chains as are well and truly laid guide
  investigation to the facts of the future those
  that are ill made fetter progress
• Wade Hampton Frost, from his
• introduction to Snow on Cholera

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A Current Definition of Epidemiology

• Epidemiology is the study of the distribution
  and determinants of health-related states and
  events in defined populations, and the
  application of this study to the control of
  health problems.
• (Last 1995)

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What is Health?

• Health is a state of complete
• physical, mental and social
• well-being and not merely
• the absence of disease
• or infirmity.
• (WHO 1948)

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The Absence of Health

• Disease
• Illness
• Sickness

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• Understanding societal patterns of health and
  disease requires acknowledging the inextricable
  and ongoing intermingling at all levels of
  the social and the biologic.
• (Nancy Krieger, 1994)

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Changes in the Distribution and Determinants of
Disease

• Public Health
• nutrition and housing
• sanitation and water
• surveillance
• lifestyle

• Preventive Medicine
• early screening and
• diagnosis
• immunizations
• Clinical Medicine
• enhanced diagnostic
• capabilities
• treatment advances

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Introduction

• Using epidemiology
• The Uses of Epidemiology (Morris)
• Why epidemiology is the basic science of public
  health
• The relationship of epidemiology to the core
  public health functions of assessment, policy
  development and assurance
• Answering prevention questions

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The Uses of Epidemiology

• The main use of epidemiology is to discover
  causes of disease so as to increase
  understanding, and hopefully also help improve
  the condition of the people.
• (J.H. Morris, 1975)

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Uses of Epidemiology

• Causation
• Genetic factors
• Environmental factors
• (including lifestyle)

Good health
Ill health
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Uses of Epidemiology

• Natural history

Death
Subclinical changes
Clinical disease
Good health
Recovery
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Uses of Epidemiology

• Description of health status of populations
• Proportion with
• ill health,
• change overtime,
• change with age,
• etc.
• Time

Good health Ill health
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Uses of Epidemiology

• Evaluation of intervention
• Treatment
• Medical care
• Health promotion
• Preventive measures
• Public health services

Good health
Ill Health
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Core Public Health Functions

• Assessment
• Policy development
• Assurance

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Answering Prevention Questions

• Are we doing the right things?
• Etiologic studies
• Studies of prevention interventions
• Are we doing things right?
• Program evaluation

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If the only tool you have is a hammer, all of
your problems will look like nails Mark Twain
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Levels of Prevention

• Primary Prevention
• Prevention of the occurrence of disease through
• General health promotion
• Specific preventive measures
• (Mausner and Bahn)

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Levels of Prevention

• Secondary Prevention Involves
• Curing disease at the earliest stage possible
• Slowing disease progression
• Preventing complication
• Limiting disability
• (Mausner and Bahn)

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Levels of Prevention

• Tertiary Prevention
• Consists of limitation of disability and
  rehabilitation where disease has already occurred
  and left residual damage
• (Mausner and Bahn)