EPB PHC 6000 EPIDEMIOLOGY FALL, 1997

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EPI 2110, Fall 2004 Principles of Epidemiology
Instructor
Kevin E. Kip, Ph.D. Assistant Professor,
Epidemiology and Medicine, Graduate School of
Public Health, Epidemiology Crabtree Hall,
kipk_at_edc.pitt.edu
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COURSE OBJECTIVES
Upon completion of this course, the student
will 1. Understand the history and role of
epidemiology as the basic science for Public
Health. 2. Develop a population-based
perspective of disease and other health-related
events. 3. Recognize ethical and professional
issues in the conduct of epidemiologic
research. 4. Calculate and interpret
epidemiologic measures of disease occurrence.
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COURSE OBJECTIVES (cont.)
5. Calculate and interpret measures of effect
used to compare the risk of disease between
populations and subgroups. 6. Understand
features, strengths, and limitations of
descriptive, observational, experimental, and
genetic epidemiologic studies. 7. Distinguish
between association and causation, including
knowledge of criteria to evaluate causal
associations. 8. Understand roles of chance,
bias, and confounding in the evaluation of
epidemiologic research.
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COURSE OBJECTIVES (cont.)

• 9. Understand the concept of effect measure
  modification.
• 10. Understand the dynamics on infectious disease
  transmission and methodology used to investigate
  an epidemic outbreak.
• 11. Understand the role of screening and public
  health surveillance in applied epidemiology.
• 12. Recognize the impact of racial, ethnic, and
  cultural variability in epidemiologic research.

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Unit 1 Introduction to Epidemiology
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• Unit 1 Learning Objectives
• Distinguish between the concepts of disease and
  health.
• Define and understand the uses of epidemiology.
• Distinguish between public health, epidemiology,
  and clinical medicine.
• Recognize major historical contributions in
  epidemiology.
• Understand the inter-disciplinary nature of
  epidemiology.

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• Unit 1 Learning Objectives (cont.)
• Understand the epidemiologic transition of
  causes of mortality from developing to developed
  countries.
• Understand practical, ethical, and professional
  issues in conducting epidemiologic research.
• Recognize the role of Institutional Review Boards
  in overseeing the conduct of epidemiologic
  research.
• Understand the natural history of disease
  progression.
• Distinguish between primary, secondary, and
  tertiary levels of disease prevention.

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Assigned Readings Textbook (Gordis) Chapter 1
-- Introduction Chapter 20 Ethical and
Professional Issues in Epidemiology Chapter 5,
pages 95-96 (Natural history of disease World
Health Report 2003, Chapter 1 Global health,
todays challenges, pages 1-22.
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DEFINITIONS OF DISEASE

• MULTIPLE DEFINITIONS (E.G.)
• An abnormal condition of an organism or part,
  especially as a consequence of infection,
  inherent weakness or environment stress, that
  impairs physiological functioning. (1973)

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DEFINITIONS OF DISEASE

• Literally, DIS-EASE, the opposite of ease, when
  something is wrong with a bodily function.
• The words disease, illness and sickness
  are loosely interchangeable, but are better
  regarded as not wholly synonymous.

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DEFINITIONS OF DISEASE

• Thus, M.W. Susser has suggested that they be
  used as follows
• - Disease is a physiological/psychological
  dysfunction.
• - Illness is a subjective state of the person
  who feels aware of not being well.
• - Sickness is a state of social dysfunction,
  i.e., a role that the individual assumes when
  ill. (1995)

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PRACTICAL DEFINITION OF DISEASE AND EXPOSURE

• Disease broad array of health conditions that we
  seek to understand and ultimately modify,
  including physiologic states, mental health, and
  the entire spectrum of human diseases (synonym
  outcome variable).
• Exposure a catch-all term for agents,
  interventions, conditions, policies, and anything
  that might affect health (synonym
  predictor/explanatory variable).

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DEFINITIONS OF HEALTH

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

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DEFINITIONS OF HEALTH (contd)

• The word health is derived from the old
  English HAL meaning hale, whole, sound in wind
  and limb.
• The state of an organism functioning normally
  without disease or abnormality. (1973)

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Discussion Question 1
When we think of studying disease, is disease
a stable concept?
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Discussion Question 1
Probably not, because 1. Cultural values can
influence definitions and perceptions of disease
(especially psychiatric disorders). 2. Improvement
s in diagnostic instrumentation can lead to
earlier detection of asymptomatic
disease. 3. Clinical thresholds for disease
classification change over time.
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EPIDEMIOLOGY

• Greek EPI - Upon
• DEMOS - People
• LOGOS - Study of, Body of Knowledge

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DEFINITIONS OF EPIDEMIOLOGY

• The study of the distribution and determinants
  of disease frequency in human populations.
  (1970)
• The study of the distribution and determinants
  of health-related states or events in specified
  populations, and the application of this study to
  control of health problems. (1988)

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DEFINITIONS OF EPIDEMIOLOGY

• The underlying premise of epidemiology is that
  disease not occur at random, but rather in
  patterns that reflect the operation of underlying
  factors.

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DEFINITIONS OF PUBLIC HEALTH

• The science and art of
• 1) preventing disease
• 2) prolonging life and
• 3) promoting health and efficiency
• through organized community effort.
• (1920)

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DEFINITIONS OF PUBLIC HEALTH (contd)

• To fulfill societys interest in assuring
  conditions in which people can be healthy.
• The field of health science concerned with
  safeguarding and improving the physical, mental
  and social well-being of the community as a
  whole. (1992)

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THE CONTENT OF PUBLIC HEALTH PRACTICE

• Focus on primary prevention.
• Community protection through monitoring and
  surveillance for infectious and toxic agents.
• Response to unanticipated natural and
  human-generated disasters.
• Health promotion through programs to notify and
  educate the community about risks and protective
  measures.
• Target hard-to-reach populations with clinical
  services.

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Why is epidemiology the basic science of public
health?

• PUBLIC HEALTH WORKS BY
• Defining a health problem
• Identifying risk factors associated with the
  problem
• Developing and testing community-level
  interventions to control or prevent the causes
  of the problem
• Implementing interventions to improve the
  health of the population and
• Monitoring those interventions to assess their
  effectiveness

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• EPIDEMIOLOGY HAS THE METHODOLOGY TO
• Determine the extent of disease in the
  community
• Study the natural history and prognosis of
  disease
• Identify associations and potential etiology
  (causes) of a disease and risk factors for
  disease
• Evaluate new preventive and therapeutic
  measures and new modes of health care delivery

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• EPIDEMIOLOGY HAS THE METHODOLOGY TO
• Provide a foundation for developing public
  policy and regulatory decisions relating to
  environmental problems.
• In short, the primary goal of epidemiology is
  to measure relationships between exposures and
  health outcomes these may provide a basis for
  public health initiatives and policies.

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THE RELATIONSHIP BETWEEN EPIDEMIOLOGY CLINICAL
PRACTICE

• Clinical Practice Uses Population Data
• Diagnoses are defined and determined from large
  groups of patients.
• Prognosis is based on experience of large
  groups of patients with the same disease, stage
  of disease, and treatments.
• Selection of therapy is based on the results of
  large treatment studies, such as clinical trials.

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Discussion Question 2
Why do we study the epidemiology of diseases in
large populations, such as the community, rather
than focusing on treatment settings?
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Discussion Question 2
Because 1. Early development of disease can be
assessed more readily in the community. 2.
Many individuals with disease do not seek
treatment. 3. Many individuals with disease do
not have access to or the resources to receive
treatment.
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Discussion Question 2

• Because
• 4. The co-occurrence of multiple diseases, and
  ascertainment of familial risks, is better
  accomplished through an epidemiological
  framework.
• 5. Threshold levels between sub-clinical and
  clinical disease are better determined from
  individuals not in treatment settings.