Epidemiology and Lecture 1

Define epidemiology
The study of how disease is distributed in populations and the factors that influence or determine this distribution

Describe the importance of defining the population under study
The source of information can be as important as the information itself

What is classical epidemiology
the population under study typically is quite inclusive and defined in rather general terms (e.g., all women of reproductive age in the USA)
– Endeavors to characterize the occurrence/distribution and determinants of disease among individuals within a community
– Classical epidemiology is sometimes thought of as the “ecology of human health and disease” or “medical ecology”

What is clinical epidemiology
the population typically is restricted to people already diagnosed with, and possibly receiving treatment for, a particular disease (e.g., all women of reproductive age in the USA with a first-time Pap smear diagnosis of high-grade cervical dysplasia made within the past year …)
– Examines factors related to disease states within ill/diseased populations that may impact on the progression of the disease process

Describe how population data are applied to the practice of clinical medicine
– The idea that an individual patient can be representative of a population of similar individuals is critical to the idea of practicing evidence-based medicine (EBM).
– Based upon available health-related data derived from studying a population of people who are similar to my patient, I can understand something about the health/disease status of my patient

Explain the various aspects of disease that can be addressed in epidemiologic studies
1. Defining features of the disease
– How can the disease be reproducibly diagnosed?
2. Risks for developing disease
– Predisposition for disease development; contributes to mechanisms of disease
– BEINGS model
3. Etiology of disease (risks and underlying cause)
– Biologic*
– Social and environmental
4. Process and Outcome of disease
– Pathophysiology*
– Prognosis

Through the illustration of the “Central Dogma of Disease, ” describe how epidemiology and epidemiologic principles are integral to patient care
Patients will present differently dependent upon where they are in the disease process. This means the doctor will have a specialized DDx and patient management plan.
– bottom line is intervention

Explain the “BEINGS” model of disease risk and provide a clinical example for each component in this model
Biologic and Behavioral factors
Environmental factors
Immunologic factors
Nutritional factors
Genetic factors
Services; Social and Spiritual factors

Describe the “Epidemiologic Triad” and define the role of each component in this triad
The underlying cause of many diseases, especially infectious diseases, can be thought of in terms of a triad of factors:
(1) the host (i.e, the person affected);
(2) the agent (e.g., the infectious organism); and
(3) the environment.

Describe how the vector factors into this model “Epidemiologic Triad”
In many instances it is important to consider a 4th factor of the triad, the vector: CRUCIAL IN PROPOGATION OF DISEASE.
– Insects, arthropods, animals
– must have a specific relationship with the host

Use malaria and measles as disease examples to illustrate the role of the various components of the triad regarding disease etiology

Consider and describe how disease intervention plans can address specific components of the triad, using measles and malaria as examples

Describe four (4) general goals of epidemiologic studies
1. Identify the extent of disease in population

2. Identify risk factors / etiology

3. Study disease progression and prognosis

4. Evaluate existing approaches to prevention and intervention

Describe four (4) general applications of epidemiologic studies
1. Plan health services/facilities

2. Develop prevention programs

3. Develop effective interventions

4. Assess resource allocation and adjust where appropriate

Define the term “epidemic”
the unusual occurrence of disease

Provide a general outline of the procedure for investigating an epidemic
Q: why did this person become sick with this disease at this time and place?

1. Disease: establish Dx / case definition
– Does the occurrence of this case represent a true epidemic?
2. Time: timing of cases
– Clues to exposure, routes of spread
– Primary vs. secondary cases (person-to-person)
3. Place
– Distribution of cases
4. Person
– Characteristics of person affected

Define the term “endemic”
disease occurs within a population at a relatively constant level

When does a risk become an etiological factor?
When the disease process has begun

What is a distribution
Who in the population is affected

What are determinants
What factors contribute to disease

What is a prognosis
How does the disease process progress and what are the typical out comes

What defines a population
Marital Status
Other (more specific)

What are the two types of epidemiology

In one word, what is classical epidemiology concerned with

In one word, what is clinical epidemiology concerned with

What is critical to the ideas of practicing evidence based medicine
The idea that an individual patient can be representative of a population of similar individuals

What are risks for developing disease (generally speaking)
– Predisposition for disease development; contributtes to mechanisms of disease
– BEINGS model

What is epidemiology primarily concerned with
1. Identifying risk factors and causes for disease
2. Identifying disease outcomes

– not so much on the “how” or the biological mechanisms

What is the attack rate
Attack rate = the number of new cases divided by the number of persons exposed (times 100 for a percent)

What is the attack rate used for
Used to determine an epidemic over time

What is a spot map
A simple and useful technique for looking at geographic patterns; it may show a cluster or patterns