1. Applied Epidemiology Seminar 2
Kaplan University

2. Chapter 2: Practical Applications of Epidemiology
Introduction
Applications for the Assessment of the Health Status of Populations and Delivery of Health Services
Applications Relevant to Disease Etiology
Conclusion

3. Introduction
This chapter provides a broad overview of the range of applications of the epidemiologic approach

4. EXHIBIT 2-1: Seven Uses of Epidemiology
Read it after the seminar to get a sense about uses of epidemiology.

5. Applications for the Assessment of the Health Status of Populations and Delivery of Health Services

6. 1. Historical Use of Epidemiology: Study of Past and Future Trends in Health and Illness
Example: Study of changes in disease frequency over time (secular trends).
Some illnesses have shown dramatic changes in industrialized nations from the beginning of modern medicine.
Chronic conditions have replaced acute infectious diseases as the major causes of morbidity and mortality.

7. Changes in Mortality
Figure 2-1 (page 53) Leading causes of mortality, 1990 and 2003.
Figure 2-2 (page 55) Age-adjusted death rates for selected causes in the USA from to 2003.

8. Conditions Affecting Reliability of Observed Changes (Page 54)
Lack of comparability over time due to altered diagnostic criteria
Aging of the general population
Changes in the fatal course of the condition

9. Four Tends in morbidity and morality
Disappearing disorders
Residual disorders
Persisting disorder
New epidemic disorders
Read the textbook, and give an example for each category.

10. 2. Predictions about the Future
The study of population dynamics in relation to sources of morbidity and mortality reveals much about possible future trends in the health of a population
Population dynamics: changes in the size and age composition of population and the processes influencing those changes.

11. Figure 2-3: Sex and Age Structure
Population pyramid: different structures for developed and developing countries.
More rectangular versus Triangular
With continuing advances in medical care, there will be an increasingly aging population in developed countries.
Needs in heath care services due to population structure changes (aging).
Page

12. Population Dynamics and Epidemiology
Population characteristics are related to the pattern of health problems.
Three factors affecting size of population: births, deaths, and migration.
Fixed population versus a dynamic population.
Demographic transition: a shift from high birth and death rates to much lower birth and death rates.

13. Epidemiology Transition
Epidemiology transition: a shift in terms of morbidity and mortality from infectious and communicable diseases to chronic, degenerative diseases.
The epidemiology transition accompanies the demographic transition.
The demographic transition, is not without its own set of consequences.

14. Health of Community Epidemiology as a descriptive tool
Potential role of epidemiology in policy evaluation

15. Epidemiology as a descriptive tool
Please read Exhibit 2-2 (page 60) Descriptive Variables for the Health of the Community.
Why are we interested in these variables?
Healthy People 2010-Goal 2: Eliminate Health Disparity. What is health disparity (page 62)?
Race differences in infant mortality, an indicator of community health (page 63).

16. Epidemiology in policy making and evaluation
Policy cycle: examination of population health, assessment of potential interventions, alternative policy choices, policy implementation, and policy evaluation.
Figure 2-5 (page 65) Factors influencing policy decision-making.

17. EXHIBIT 2-3 Case Study
Using Epidemiologic Methods to Conduct a Policy Evaluation of the Smokfree Bars Law.

18. Working of Health Services: Operations research and Problem Evaluation
Operations research: the study of the placement of health services in a community and the optimum utilization of such services.
Examples of questions asked (box on page 68).

19. Examples for operations research
Dr. Friis’ study
National Ambulatory Medical Care Survey

20. NAMCS
The National Ambulatory Medical Care Survey (NAMCS) is a national survey designed to meet the need for objective, reliable information about the provision and use of ambulatory medical care services in the United States. Findings are based on a sample of visits to non-federal employed office-based physicians who are primarily engaged in direct patient care.

21. Applications Relevant to Disease Etiology
Causality in Epidemiologic Research
Risk Factors Defined
Modern Concepts of Causality
Study of Risks to Individuals
Enlargement of the Clinical Picture of Disease
Prevention of Disease

22. Causality in Epidemiologic Research
As an observational science, epidemiology is frequently subject to criticism.
Part of the reason for the skepticism about epidemiologic research is the inability of the discipline to “prove” anything.

23. Henle-Koch Postulates
3 of 4 criteria (page 72): Agent present in every case of the disease, one agent-one disease, exposure of healthy subjects to suspected agents.
Instrumental in efforts to prove (or disprove) the causative involvement of a microorganism in a pathogenesis of an infectious disease.
3 issues in Henle-Koch postulates (pure determination) (page).

24. CVD Example
It is now widely accepted that there is no single causal agent but rather multiple factors that produce chronic disease such as CVD.
Triad of host, agent, and environment
The triad is no longer satisfactory, suggested by Cassel (page 73)

25. Risk Factors Defined
Because of uncertainty of “causal” factors in epidemiologic research, it is customary to refer to an exposure that is associated with a disease as a risk factor.
Three requisite criteria for risk factors.
The frequency of the disease varies by category or value of the factors
The risk factors must precede the onset of disease
The observed association must not be due to any source of error.

26. Modern Concepts of Causality
Causal inferences gained increasing popularity as a topic of formal discussions as a result of findings (in the early 1950s) regarding the association between smoking and lung cancer.

27. Criteria of judgment of causality
Sir Austin Bradford Hill (1965)
Strength of association
Time sequence
Consistency of relationship upon repetition
Specificity of association
Coherence of explanation.
See EXHIBIT 2-4 (page 75)

28. Nine Aspects of an Empirical Association to consider
when one is trying to decide whether an association is consistent with cause and effect.
5 criteria + the following 4
Biological gradient (dose-response curve, Figure 2-7)
Plausibility
Experiment
Analogy

29. Study of Risks to Individuals
Epidemiologic research on disease etiology typically involves collection of data on a number of individual members of different study groups or different study populations.
Two important study designs (case-control and cohort study, to be covered late).

30. The issue of whether the results of an epidemiologic study influence clinical decision-making is in part determined by the criteria of causality
Extrapolation to the individual from finds based on observations of groups should be made with caution.

31. The effect size of the risk and the rarity of a disease determine if the risk is deemed as important.
Public health implications: a risk factor may be relatively unimportant for individuals indeed may be important for the public (Chapter 9).

32. Prediction of prognosis and survival
It is possible to predict the individual’s prognosis and likelihood of survival if afflicted by a serious disease.
Such information can be used to inform the patient about his or her chance for survival and ultimate recovery.
Example: Figure 2-8 (page 83) 5-year cancer survival rate. Which cancer has the highest survival rate? Which has the lowest?

33. Enlargement of the Clinical Picture of Disease
When a new disease first gains the attention of health authorities, usually the most dramatic cases are the ones observed initially.
Late epidemiologic studies may reveal that the disease is less severe in the population.
More studies are needed to develop a complete clinical picture of the disease

34. Prevention of Disease
Natural history of disease: the course of disease from its beginning to its final clinical end points.
Pre-pathogenesis phase
Pathogenesis phase

35. Three Strategies for Disease Prevention
Primary Prevention
Secondary Prevention
Tertiary Prevention

36. Primary Prevention Occurs during the period of pre- pathogenesis.
Includes health promotion and specific protection against disease
Examples? On page 85