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.