Transcript Dr. Chris Cochran Associate Professor 895-1400 HCA 202: Epidemiological Concepts for Health

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 wellbeing, 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
Problem with the Model




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
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 1997
Source: 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
1400
Injuries
1200
Congenital Anomalies
1000
800
Prematurity
600
Sudden Infant Death
Syndrome
Cancer
400
200
Respiratory Disease
0
YPPL in Thousands
Incidence And Prevalence
Knowing 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.
Tracking a Single Event* for Incidence and
Prevalence
Population at
risk = 1,000
Population at
risk = 950
Number of new
cases = 25
b. IR = 25/850
IR = .029
Number of
existing cases
= 50
Number of new
cases = 100
PR = 50/1000 =
.005 (Point PR)
a. Incidence rate =
100/950 = .105 (IR)
Population at
risk = 850
What would be the
period prevalence
rate?
*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