HCA 202: Epidemiological Concepts for Health Care Managers

Dr. Chris Cochran

Associate Professor

895-1400

Course Outline

Description of course syllabus The descriptive nature of epidemiology Using epidemiological analytical tools for

investigating disease, illness and injuries Applying epidemiological tools to the health

care industry Class presentation

What is Health

A state of complete physical, mental and social well-being, not merely the absence of disease or infirmity (WHO).

Preventing premature death and preventing disability, preserving a physical environment that supports human life, cultivating family and community support, enhancing each individual’s inherent abilities to respond to and to act, and assuring that all Americans achieve and maintain a maximum level of functioning. (Healthy People 2010)

Earliest definition of Epidemiology

“Whoever wishes to pursue properly the science of medicine … ought to consider:

The effects of the season of the year The hot winds and the cold The properties of the waters The setting of the town The behavior of the people

Hippocrates

Relationship between Education and Income

What is Epidemiology

Old: Science of the distribution of diseases of mankind (1889).

Course definition: The study of the distribution and determinants of diseases and injuries in human populations.

Think about these two definitions in their context, why does the second one apply more today than the earlier version?

The Relationship of Epidemiology to Health Care Managers

To understand the increase/decrease in size of service populations

To understand the characteristics and health status of the population for planning purposes

To understand the consequences of health care problems To mesh the service organizations to the needs of the

population To monitor performance by the organizations To modify the structure and processes and respond to

environmental change To better formulate and evaluate public policy

Reported Cases of Gonorrhea per 100,000 population

Life Expectancy at Birth

Life Expectancy at Birth and at age 65 years 1900, 1950, and 2000

THE EPIDEMIOLOGICAL TRIAD

HOST

VECTOR

AGENT ENVIRONMENT

Developed primarily for infectious diseases Shifts in disease patterns have diminished the

agent’s role and broadened the scope of host and environment

Relies on the assumption of a single cause/single effect model (multiple factors may be at play)

Does not include enough about illness or injury

Problem with the Model

Classification for Health Status Today

Disease – a state of dysfunction of the normal physiological processes manifested as signs, symptoms, and abnormal physical or social function (includes injury).

Functional Ability – a process used to represent how independently an individual can perform or fulfill expected social roles (physical and mental).

Quality of Life – multidimensional concepts of measures covering symptoms/problem complexes, mobility, physical activity, emotional well-being and social functioning.

Descriptive Epidemiology

Using Rates to Give a Snapshot of Health

The Four Factors Affecting Health

Environment (physical and social) Lifestyle/Behavior Biology (Gene pool) Health care services

Practical Use of Determinants of Health

Prevention and Health Promotion

Primary – inhibition of the development of the disease before it occurs

Secondary – early detection and treatment of a disease

Tertiary – the rehabilitation or restoration of effective functioning

Primary Cause of Death 1900

Primary Cause of Death 1997Source: Healthy People 2010

Comparing U.S. with Other Countries

Healthy People 2010 Site See Death rates by country See primary causes of death by age group

Descriptive Epidemiology – Understanding Person, Place and Time

Person Measures– Age– Sex– Ethnic group and race– Social class/social-economic status

Place Measures

Place – related by natural barriers or by political boundaries.– Natural boundaries – characterized by particular

environmental or climatic condition (temperature, humidity, rainfall, altitude, mineral content, etc.).

– Place diseases – parasitic diseases that may be due to certain factors such as tropics, temperate, or other conditions.

– Political subdivisions – vary from entire nations to counties, cities, towns, and boroughs

Time and Place

Time – basic aspect of epidemiology– Secular trends (long-term variations, which occur

over periods of time including years and decades). Good for studying "birth cohorts".

– Cyclic change – recurrent alteration in the frequency of disease (seasonal changes, for example – influenza)

Clusters in time and place – difficult to determine the significance of linkages because there is no defined denominator

Using Rates In Epidemiology

Numerator - the number of people/cases with the disease

Denominator - (the population at risk)

Basic Descriptive Rates

Rate - Number of events, cases, or deaths in a time period/Population in same area

Ratio – Expresses the relationship between 2 numbers in the form of x:y or (x/y)k.

Proportion – Specific type of ratio with the resultant value expressed as a percent.

DEATH RATES

Three essential components of death rates:– A population group exposed to the risk of death– A time period– The number of deaths occurring in the population

during that time period (NOTE: best to take the population for the mid-point of the period being studied.

Types of Rates

Crude Death Rate:– Total # deaths from all causes during a 12 month period

Total # persons in the population at the midpoint of the period

– Usually X 1,000 (or measured as number of deaths per 1,000 pop.)

Cause specific death rates:– # deaths from a specific disease # persons in the

population at the midpoint of the period– Usually X 100,000

Types of Rates

Age specific death rates:– # deaths in a specific age group # persons in

that age group; Usually X 100,000  Case fatality rate: Represents the risk of

dying over a specified period of time for people with a certain disease–  # persons dying during a specified time period

after disease onset or diagnosis # persons with the specified disease

Rates and Ratios Continued

Proportionate mortality ratio: – Represents the proportion of total deaths that are

due to a specific cause. – Does not represent the risk of dying.– # deaths from a specific disease Total #

deaths in the population X 100 to express as a percent

Other Rates To Consider

Gender Specific Race Specific Infant Mortality Rates

– Infant Mortality Rate – Birth to 1 year; Denominator is live births

No. of deaths < 1 year of age/No. of live births – Neonatal Mortality Rate – Post-neonatal Mortality Rate – Perinatal Mortality Rate

Years of Productive Life Lost before Age 65 among Children less than 20 Years

0

200

400

600

800

1000

1200

1400

YPPL in Thousands

Injuries

Congenital Anomalies

Prematurity

Sudden Infant DeathSyndromeCancer

Respiratory Disease

Incidence And PrevalenceKnowing Which Is Which

Incidence measures the number of new cases in an at-risk population

Prevalence measures the number of existing cases in an at-risk population

Point Prevalence - the number of existing cases of a disease at a specific period of time. This includes new cases (Incidence).

Period Prevalence - refers to the number of cases during a period or interval. This can include new and recurring cases.

Population at risk = 1,000

Number of existing cases = 50

Population at risk = 950

PR = 50/1000 = .005 (Point PR)

Number of new cases = 100

a. Incidence rate = 100/950 = .105 (IR)

Population at risk = 850

Number of new cases = 25

b. IR = 25/850 IR = .029

What would be the period prevalence rate?

 

Tracking a Single Event* for Incidence and Prevalence

*refers to only one occurrence of the event per person

Uses of Incidence and Prevalence

Prevalence is useful as planning tool Can be used to express burden of some attribute in

the population Can monitor control programs for chronic illness Point prevalence can track illness over time Incidence rates are fundamental tools for etiologic

studies of acute and chronic illness

Uses of Incidence and Prevalence

Comparing incidence between groups is useful for measuring affects of risk between populations

High prevalence does not signify risk, it may merely reflect a change in survival rate

Low prevalence may reflect a rapidly fatal disease (or easily curable)

Prevalence favors inclusion of chronic illness over acute illness