HCA 202: Epidemiological Concepts for Health Care Managers

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HCA 202 Epidemiological Concepts for Health Care
Managers

• Dr. Chris Cochran
• Associate Professor
• 895-1400

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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

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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 individuals
  inherent abilities to respond to and to act, and
  assuring that all Americans achieve and maintain
  a maximum level of functioning. (Healthy People
  2010)

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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

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Relationship between Education and Income
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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?

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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

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Reported Cases of Gonorrhea per 100,000 population
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Life Expectancy at Birth
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Life Expectancy at Birth and at age 65 years
1900, 1950, and 2000
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THE EPIDEMIOLOGICAL TRIAD
HOST
VECTOR
AGENT
ENVIRONMENT
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Problem with the Model

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

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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.

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Descriptive Epidemiology

• Using Rates to Give a Snapshot of Health

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The Four Factors Affecting Health

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

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Practical Use of Determinants of Health
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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

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Primary Cause of Death 1900
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Primary Cause of Death 1997Source Healthy
People 2010
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Comparing U.S. with Other Countries

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

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Descriptive Epidemiology Understanding Person,
Place and Time

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

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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

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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

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Using Rates In Epidemiology

• Numerator - the number of people/cases with the
  disease
• Denominator - (the population at risk)

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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 xy or (x/y)k.
• Proportion Specific type of ratio with the
  resultant value expressed as a percent.

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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.

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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

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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

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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

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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 lt 1 year of age/No. of live births
  
• Neonatal Mortality Rate
• Post-neonatal Mortality Rate
• Perinatal Mortality Rate

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

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Tracking a Single Event for Incidence and
Prevalence
 
Population at risk 1,000
Number of existing cases 50
PR 50/1000 .005 (Point PR)
a. Incidence rate 100/950 .105 (IR)
Population at risk 950
Number of new cases 100
Population at risk 850
Number of new cases 25
refers to only one occurrence of the event per
person
What would be the period prevalence rate?
b. IR 25/850  IR .029
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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

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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