Managerial Epidemiology
Helpm31990
51589_PPTx_CH02.pptxChapter 2
Practical Applications of Epidemiology
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Learning Objectives
Discuss uses and applications of epidemiology
Define the influence of population dynamics on community health
State how epidemiology may be used for operations research
Discuss the clinical applications of epidemiology
Cite causal mechanisms from the epidemiologic perspective
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Seven Uses for Epidemiology
Health Status and Health Services
Study history of the health of populations
Diagnose the health of the community
Examine the working of health services
Disease Etiology
Estimate the individual risks and chances
Identify syndromes
Complete the clinical picture
Search for causes
Health Status and Health Services
Describing the occurrence of disease in the community
Planning for allocation of resources
Public health practitioners
Administrators
Evaluating programs, e.g., public health service programs
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Disease Etiology
Epidemiologists continue to search for clues as to the nature of disease.
Knowledge that is acquired may be helpful in efforts to prevent the occurrence.
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Historical Use of Epidemiology
Refers to the study of past and future trends in health and illness
For example: Secular trends--changes in disease frequency over time
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Examples of Trends
Chronic diseases have replaced acute infectious diseases as the major causes of morbidity and mortality.
In 2009, the leading causes of U.S. deaths were heart disease, cancer, and chronic lower respiratory disease.
Increases were reported for Alzheimer’s disease, kidney disease, and hypertension.
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Factors Affecting Reliability of Observed Changes
Lack of comparability over time due to altered diagnostic criteria
Aging of the general population
Changes in the fatal course of the condition
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Four Trends in Disorders
Disappearing
Residual
Persisting
New epidemic
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Disappearing Disorders
This category refers to conditions that were once common but are no longer present in epidemic form.
Examples include smallpox, poliomyelitis, and measles.
Brought under control by immunizations, improvement in sanitary conditions, and the use of antibiotics and other medications led to eradication of these diseases
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Residual Disorders
Conditions for which the key contributing factors are largely known
Methods of control not implemented effectively
Examples:
STDs
Perinatal and infant mortality among low SES persons
Problems associated with alcohol and tobacco use
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Persisting Disorders
Diseases for which there is no effective method of prevention or no known cure
Examples: certain types of cancer and mental disorders
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New Epidemic Disorders
Diseases that are increasing in frequency
Examples: Lung cancer, AIDS, Obesity, Type 2 diabetes
The emergence of new epidemics of diseases may be a result of increased life expectancy of the population, new environmental exposures, or changes in lifestyle, diet, and other practices.
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Predictions About the Future
A population pyramid represents the age and sex composition of the population of an area or country at a point in time.
By examining the distribution of a population by age and sex, one may view the impact of mortality from acute and chronic conditions.
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Trends in the Age and Sex Distributions
Developing countries
In 1950 and 1990, countries had a triangular population distribution, which is associated with high death rates from infections, high birth rates, and other conditions.
By 2030, improvements in health are likely to result in greater survival of younger persons, causing a projected change in the shape of the population distribution.
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Trends in the Age and Sex Distributions
Developed countries
Manifest a rectangular population distribution
Infections take a smaller toll and cause a greater proportion of children to survive into old age
Residents enjoy greater life expectancy
The population of developed countries will grow increasingly older due to continuing advances in medical care
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Population Dynamics
Denotes changes in the demographic structure of populations associated with such factors as births and deaths and immigration and emigration
Two types of populations
Fixed populations
Dynamic populations
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Population Terms
Fixed population
Adds no new members and, as a result, decreases in size due to deaths only
Examples: survivors of the 9-11 terrorist attack in New York, residents of New Orleans during Hurricane Katrina, and persons who had a medical procedure such as hip replacement
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Population Terms
Dynamic population
Adds new members through immigration and births or loses members through emigration and deaths
Example: the population of a country, city, or state in the United States
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Influences on Population Size
Three major factors affect the sizes of population births, deaths, and migration.
Population in equilibrium or a steady state
The three factors do not contribute to net increases or decreases in the number of persons.
Influences on Population Size
Population increasing in size
The number of persons immigrating plus the number of births exceeds the number of persons emigrating plus the number of deaths.
Population decreasing in size
The number of persons emigrating plus the number of deaths exceeds the number of persons immigrating plus the number of births.
Demographic Transition
Shift from high birth and death rates found in agrarian societies to lower birth and death rates found in developed countries.
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Epidemiologic Transition
Shift in the pattern of morbidity and mortality from infectious and communicable diseases to chronic, degenerative diseases.
Epidemiology and the Health of the Community
Provides a key to the types of problems requiring attention
Determines the need for specific health services
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Demographic and Social Variables
Age and sex distribution
Socioeconomic status
Family structure
Racial, ethnic, and religious composition
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Variables Related to Community Infrastructure
Availability of social and health services
Quality of housing stock
Social stability (residential mobility)
Community policing
Employment opportunities
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Health-Related Outcome Variables
Homicide and suicide rates
Infant mortality rate
Chronic and infectious diseases
Drug and alcohol abuse rates
Teen pregnancy rates
Sexually transmitted diseases
Birth rate
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Environmental variables
Air pollution from stationary and mobile sources
Access to parks/recreational facilities
Availability of clean water
Availability of markers that supply healthful groceries
Number of liquor stores and fast-food outlets
Nutritional quality of foods and beverages vended to school-children
Health Disparities
Healthy People 2010, Goal 2
“ . . . To eliminate health disparities among segments of the population, including differences that occur by gender, race, or ethnicity, . . .”
Healthy People 2020
“. . .To achieve health equity, eliminate disparities, and improve the health of all groups. . .”
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Health Disparities
Infant mortality in the U.S.
Income inequality (Gini index)
Ranges for 0 to 1
The closer the index is to one, the greater is the level of inequality.
States with the highest Gini Scores: Tennessee, Kentucky, and West Virginia
Epidemiology and Policy Evaluation
Using epidemiologic methodologies to evaluate public health policies
Examples: tobacco control, needle distribution programs, ban on plastic bags, printing of nutritional content on restaurant menus, removal of high fat and high sugar content foods from vending machines in schools, and prohibition of drivers’ use of cell phones
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Working of Health Services
Operations research (OR)
Program evaluation
Operations Research (OR)
The study of the placement and optimum utilization of health services in a community
Contribution of epidemiology to OR is the development of research designs, analytic techniques, and measurement procedures
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Examples of OR
Coordination of programs for the developmentally disabled
Studies of health care utilization
Residential care facilities
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Program Evaluation
Uses epidemiologic tools to determine how well a health program meets certain stated goals
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Epidemiology and Program Evaluation
Methods for selecting target populations
Design of instruments for data collection
Delimitation of types of health-related data
Methods for assessment of healthcare needs
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Epidemiology and Disease Etiology
Applications include:
Search for causes
Individual risks
Specific clinical concerns
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Causality in Epidemiologic Research
Epidemiologic research is the subject of criticism.
Many conflicting studies
Henle-Koch postulates are not relevant to many contemporary diseases.
Multivariate causality
Risk Factors Defined
Due to the uncertainty of “causal” factors the term risk factor is used.
Definition: exposure that is associated with a disease
Example of a risk factor: smoking.
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Risk Factors Defined (cont’d)
Three Criteria for Risk Factors
The frequency of the disease varies by category or value of the factor, e.g., light smokers vs. heavy smokers.
The risk factor precedes onset of the disease.
The observation must not be due to error.
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Modern Concepts of Causality: 1964 Surgeon General’s Report
Five criteria for causality
Strength of association
Time sequence
Consistency upon repetition
Specificity
Coherence of explanation
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Modern Concepts of Causality: Sir Austin Bradford Hill
Hill expanded the list of criteria to include:
Biologic gradient
Plausibility
Experiment
Analogy
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Study of Risks to Individuals
Etiologic study designs used
Case-control
Cohort
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Case-Control Design
A type of design that compares persons who have a disease (cases) with those who are free from the disease (controls).
This design explores whether differences between cases and controls result from exposures to risk factors.
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Cohort Design
A group of people free from a disease is assembled according to a variety of exposures.
The group (cohort) is followed over a period of time for development of disease.
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How Results Impact Clinical Decisions
The following considerations determine a study’s influence:
Criteria of causality
Relevance to each patient
Size of the risk
Public health implications
Individual vs. population
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Enlargement of the Clinical Picture of Disease
Cases of a new disease often the most dramatic cases
Need to survey a complete population
Example of a “new” disease—Legionnaires’ disease
Prevention of Disease
Research is applied to identify where in a disease’s natural history effective intervention might be implemented.
The natural history of disease refers to the course of disease from its beginning to its final clinical end points.
Natural History of Disease
Prepathogenesis--before agent reacts with host
Pathogenesis--after agent reacts with host
Later stages include development of active signs and symptoms.
Clinical end points are: recovery, disability, or death.
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Primary Prevention as a General Concept
Occurs during prepathogenesis phase
Includes health promotion and specific protection against diseases
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Primordial Prevention
Concerned with minimizing health hazards in general
Examples include improvement of:
Economic conditions
Social conditions
Behavioral conditions
Cultural patterns of living
Primary Prevention as a Specific Concept
Involves specific protection against disease-causing hazards
Examples:
Utilization of specific dietary supplements
Immunizations
Educational campaigns against unintentional injuries
Primary Prevention: Active and Passive
Active
Necessitates behavior change on the part of the subject
Examples: Vaccinations and wearing protective devices
Passive
Does not require any behavior change
Examples: Fluoridation of public water and vitamin fortifications of milk and bread products
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Secondary Prevention
Occurs during pathogenesis phase
Designed to reduce the progress of disease
Examples are screening programs for cancer and diabetes.
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Tertiary Prevention
Takes place during late pathogenesis
Designed to limit disability from disease
Also directed at restoring optimal functioning (rehabilitation)
Examples include: physical therapy for stroke patients, halfway houses for alcohol abuse recovery, and fitness programs for heart attack patients.
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