EPIDEMIOLOGY

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EPIDEMIOLOGY

• Catherine T. Horat RN MSN CS C-FNP
• NUR 410 Community Focused Nursing

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Epidemiology

• Definition
• The study of the distribution and determinants
  of health-related states or events in specific
  populations, and the application of this study to
  control of health problems
• 
  
  Last, 2001, p. 62

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Epidemiology

• Studies

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Epidemiology

• Epidemiologic Methods used in
• Health services research
• Investigate associations between
• To what extent Healthy People 2000 goals
  accomplished
• Monitor progress of Healthy People 2010

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Study of Distribution

• Distribution
• Patterns of events
• Influences on
• Characterized as

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Descriptive Epidemiology

• Based on distribution or patterns of health
  events in populations
• Attempts to describe a disease entry according to
  
• Person
• Place
• Time

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Study of Determinants

• Determinants of health events or factors that
  determine or influence the patterns of
• Questions asked

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Study of Determinants

• Include

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Analytic Epidemiology

• Investigation of causes and association
• Directed toward understanding the etiology or
  origins and causal factors of a disease
• Useful for
• Guiding or evaluating policies and programs that
  improve the health of a community

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Comparison of Analytic/Descriptive Epidemiology

• Analytic studies rely on descriptive comparisons
• Descriptive comparisons shed light on determinants

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Epidemiology

• Study of populations in order to

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Key Terms

• Surveillance
• Endemic
• Epidemic
• Pandemic

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Epidemiological Investigational Models

• Epidemiological Triangle
• Web of Causation
• Person-Place-Time

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Epidemiological Triangle
Agent
Host
Environment
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Epidemiological Triangle AGENT

• Causative factor contributing to health problems
  that must be present or lacking

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Epidemiological Triangle HOST

• A susceptible human or animal who harbors and
  supports a disease causing agent
• Intrinsic

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Epidemiological Triangle ENVIRONMENT

• All factors internal or external to a client that
  constitute the context in which the client lives
  and that influences and are influenced by the
  host and agent-host interactions

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Web of Causation

• Web of Causation
• Complex interrelationships of numerous factors
  interacting to increase or decrease risk of
  disease
• The determination based on EVIDENCE or REASONING
  process that an event or state Resulted FROM or
  was CAUSED BY some other events, exposure,
  characteristics, or a combination of them
  (Causality)

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Causality

• Criteria

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Person-Place-Time

• Examines the characteristics of
• People affected
• The place or location
• Time period involved
• Considered as variables
• Person who is affected
• Place where affected
• Time when affected

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Health Promotion and Disease Prevention

• Natural History of Disease the course of
  progression of a disease from onset to resolution
• Prepathogenesis period (Environment)
• Disease has not developed but interactions are
  occurring between host, agent and environment
  that produce disease stimulus and increase the
  hosts potential for disease
• Pathogenesis period (Human)
• Begins when disease-producing stimuli start to
  produce changes in the tissues of humans

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Natural History and Levels of Prevention

• Primary Prevention
• Prepathogenesis
• Adaptation
• Adaptive processes are initiated

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Natural History and Levels of Prevention

• Secondary Prevention
• Pathogenesis
• Discernable early lesions
• Clinical recognition
• Early DX and prompt treatment

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Natural History and Levels of Prevention

• Tertiary Prevention treatment to arrest disease
  or rehabilitation
• Clinical Disease

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Mortality Rates

• Relative death rate
• Sum of deaths in a given population at a given
  time
• Crude mortality rate
• Cause-specific mortality rate
• Case fatality rate
• Age-specific death rate
• Proportional Mortality Ratio

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Mortality Rates

• Crude mortality rate includes
• based per on 100,000 population
• deaths in a year______
• Average midyear population
• Ex
• 10,000deaths in St. Petersburg, Fl in 2002
  X 100,000
• 350,000of persons in St. Petersburg Fl
  in July 1, 2002

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Mortality Rates

• Cause-specific actual cause of deaths desired to
  be measured
• per 100,000
• EX
• 75 of men who died from pneumonia in St.
  Petersburg Fl in 2003 X100,000
• 60,000 of men in total
  population of St. Petersburg, FL, 2003

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Mortality Rates

• Case-fatality
• deaths due to a specific disease X100
  cases
• cases of specific disease
• EX
• 25 deaths from E-coli X 100 cases
• 300 cases of E-coli

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Mortality Rates

• Age-specific
• Enables comparing populations in different
  locations
• EX
• 120 deaths among 45 year olds in Denver CO in
  2005 X 100000
• 10,000 of 45 year old people in Denver CO
  July 1

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Mortality Rates

• Proportional
• Compares number of deaths from a particular cause
  with deaths from all other causes
• deaths from specific cause in a specified time
  period X 100
• Total deaths in same time period
• 200 of Cancer deaths in 2001
  X 100
• 5000 of total deaths from all causes in 2001

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Morbidity Rates

• Relative incidence of disease
• Incidence
• Prevalence

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Morbidity Rates

• Incidence
• Rates that measure ALL NEW CASES arising in a
  population during a defined period of time,
  usually 1 year
• of new cases in place during time of
  observation X K
• Population in place at midpoint of
  time
• 60 new mump cases from 1/07 to
  1/08 X 100,000
• 50,000 population
• K unit of population

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Morbidity Rates

• Prevalence measures total number of persons with
  a characteristic with the total number in the
  population
• 50 people with chicken pox X K
• 1000 people in population