assignment week 1 Managerial Epidemiology
Chapter 2
Practical Applications of
Epidemiology
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
Seven Uses for Epidemiology • Health Status and Health Services
1. Study history of the health of populations
2. Diagnose the health of the community
3. Examine the working of health services
• Disease Etiology
1. Estimate the individual risks and chances
2. Identify syndromes
3. Complete the clinical picture
4. 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
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.
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
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.
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
Four Trends in Disorders
• Disappearing
• Residual
• Persisting
• New epidemic
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
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
Persisting Disorders
• Diseases for which there is no effective
method of prevention or no known cure
• Examples: certain types of cancer and
mental disorders
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.
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.
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.
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
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
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
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
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.
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
Demographic and Social
Variables
• Age and sex distribution
• Socioeconomic status
• Family structure
• Racial, ethnic, and religious
composition
Variables Related to
Community Infrastructure
• Availability of social and health
services
• Quality of housing stock
• Social stability (residential mobility)
– Community policing
– Employment opportunities
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
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. . .”
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
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
Examples of OR
• Coordination of programs for the
developmentally disabled
• Studies of health care utilization
• Residential care facilities
Program Evaluation
• Uses epidemiologic tools to
determine how well a health program
meets certain stated goals
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
Epidemiology and Disease
Etiology
• Applications include:
–Search for causes
–Individual risks
–Specific clinical concerns
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.
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.
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
Modern Concepts of Causality:
Sir Austin Bradford Hill
• Hill expanded the list of criteria to
include:
– Biologic gradient
– Plausibility
– Experiment
– Analogy
Study of Risks to Individuals
• Etiologic study designs used
• Case-control
• Cohort
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.
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.
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
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.
Primary Prevention as a
General Concept
• Occurs during prepathogenesis
phase
• Includes health promotion and
specific protection against diseases
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
Secondary Prevention
• Occurs during pathogenesis phase
• Designed to reduce the progress of
disease
• Examples are screening programs for
cancer and diabetes.
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.