Transcript EPB PHC 6000 EPIDEMIOLOGY FALL, 1997

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,
[email protected]
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.
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.
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.
Unit 1:
Introduction to Epidemiology
Unit 1 Learning Objectives:
1. Distinguish between the concepts of
disease and health.
2. Define and understand the uses of
epidemiology.
3. Distinguish between public health,
epidemiology, and clinical medicine.
4. Recognize major historical contributions in
epidemiology.
5. Understand the inter-disciplinary nature of
epidemiology.
Unit 1 Learning Objectives (cont.):
6. Understand the “epidemiologic transition” of
causes of mortality from developing to
developed countries.
7. Understand practical, ethical, and professional
issues in conducting epidemiologic research.
8. Recognize the role of Institutional Review
Boards in overseeing the conduct of
epidemiologic research.
9. Understand the natural history of disease
progression.
10.Distinguish between primary, secondary, and
tertiary levels of disease prevention.
Assigned Readings:
Textbook (Gordis):
Chapter 1 -- Introduction
Chapter 20 – Ethical and Professional
Issues in Epidemiology
Chapter 5, pages 95-96 (Natural
historyof disease
World Health Report 2003, Chapter 1:
Global health, today’s challenges,
pages 1-22.
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)
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.
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)
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).
DEFINITIONS OF HEALTH
• WHO: A state of complete physical,
mental, and social well-being and not
merely the absence of disease or
infirmity. (1948)
DEFINITIONS OF HEALTH (cont’d)
• 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)
Discussion Question 1
When we think of studying “disease”,
is “disease” a stable concept?
Discussion Question 1
Probably not, because:
1. Cultural values can influence definitions
and perceptions of disease (especially
psychiatric disorders).
2. Improvements in diagnostic
instrumentation can lead to earlier
detection of asymptomatic disease.
3. Clinical thresholds for disease
classification change over time.
EPIDEMIOLOGY
Greek:
EPI - Upon
DEMOS - People
LOGOS - Study of, Body of
Knowledge
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)
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.
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)
DEFINITIONS OF PUBLIC HEALTH (cont’d)
• To fulfill society’s 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)
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.
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
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
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.
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.
Discussion Question 2
Why do we study the epidemiology
of diseases in large populations,
such as the community, rather than
focusing on treatment settings?
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.
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.