Introduction to Epidemiology: Epidemiology as a Population Science. Basic Epidemiology Measures - PowerPoint PPT Presentation

Loading...

PPT – Introduction to Epidemiology: Epidemiology as a Population Science. Basic Epidemiology Measures PowerPoint presentation | free to download - id: 459513-ZTcxN



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Introduction to Epidemiology: Epidemiology as a Population Science. Basic Epidemiology Measures

Description:

In the Internet Era Introduction to Epidemiology Epidemiology as a Population Science Basic Epidemiology Measures Thomas Songer, PhD Counts Limited Interpretation ... – PowerPoint PPT presentation

Number of Views:1204
Avg rating:3.0/5.0
Slides: 41
Provided by: Thoma402
Learn more at: http://www.pitt.edu
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Introduction to Epidemiology: Epidemiology as a Population Science. Basic Epidemiology Measures


1
Introduction to Research Methods In the Internet
Era
Introduction to Epidemiology
Epidemiology as a Population Science Basic
Epidemiology Measures
Thomas Songer, PhD
2
Key Lecture Concepts
  • Understanding epidemiology as a science focused
    on populations
  • Samples of the population are taken to assess
    health issues
  • Health outcomes data can be expressed through
    multiple measures
  • These measures can be expressed as differing
    metrics

2
3
What is Epidemiology?
3
4
Epidemiology
  • Epidemiology is the study of the determinants,
    distribution, and frequency of disease in human
    populations
  • Who gets disease and why
  • Epidemiologists study sick and well people to
    determine the crucial difference between those
    who get disease and those who are spared

4
5
Purpose of Epidemiology
  • To provide a basis for developing disease control
    and prevention measures for groups at risk. This
    translates into developing public health measures
    to prevent or control disease.

5
6
Population Focus
  • The focus of epidemiology is on the occurrence of
    health and disease in the population. 
  • What happens to many
  • The population approach contrasts with clinical
    medicines primary concern with health and
    disease in the individual. 
  • What happens to one

6
7
Health as a manifestation of individuals in
social groups
  • Humans are social animals.
  • Many diseases are caused only by the interaction
    of individuals within and between populations.
  • Disease and health outcome patterns are generated
    in and by populations and need to be described,
    explained and predicted in a population setting.

Bhopal 2002
7
8
What is a Population?
  • The common definition of a population is All the
    inhabitants of a given country or area considered
    together 
  • A population can also be groups of individuals
    that share a common thread
  • Clinical populations
  • Subgroups of the population by age, race, etc

8
9
Epidemiology as a population science
  • Diseases are expressed biologically in
    individuals, however, no epidemiological study
    can be done on one person
  • Epidemiology studies humans in the aggregate
    (i.e. groups)
  • Conclusions are directly applicable to the groups
    studied
  • Conclusions are only indirectly applicable to
    individuals

Bhopal 2002
9
10
Epidemiology is
  • The study of disease and its treatment, control,
    and prevention in a population of individuals.
  • Whole populations may be examined, but
  • More frequently, samples of the population may be
    examined. Samples that are studied must be
    representative of the population for the results
    to be generalized to the total population.

Torrence 1997
10
11
Descriptive Inferential Statistics
Descriptive Statistics deal with the
enumeration, organization and graphical
representation of data from a sample Inferential
Statistics deal with reaching conclusions from
incomplete information, that is, generalizing
from the specific sample Inferential
statistics use available information in a sample
to draw inferences about the population from
which the sample was selected
Rahbar
12
Background
  • Different types of activities and practices are
    undertaken in epidemiology to develop disease
    control and prevention measures for groups at
    risk.

12
13
Broad Characterizations of Epidemiology Practices
  • Descriptive Epidemiology
  • Examining, identifying, and reporting on the
    frequency and distribution of disease in a
    population. Learning the basic features of its
    distribution.
  • Analytic Epidemiology
  • Identifying factors underlying disease or health
    events. Testing a hypothesis by studying how
    exposures relate to outcomes

13
14
Broad Characterizations of Epidemiology Practices
  • Developing interventions to reduce disease or
    improve health in the community
  • Using information from analytical studies,
    develop strategies centered around an important
    exposure factor. Test these strategies with
    clinical trials.
  • Program Evaluation
  • Examining the effectiveness of programs for
    disease control in the community

14
15
There is a logical sequence to the practice of
epidemiology in disease prevention
Descriptive Analytical Interventions Programs
Disease prevention
15
16
Basic Question in Research
  • Are exposure and disease/outcome linked?

Is there an association between them?
E
D
Exposure
Disease / Health Outcome
16
17
Health outcomes in research studies may be
expressed through multiple types of measures
17
18
Basic Measurements of Disease or Health Outcome
Frequency in Epidemiology
  • Measurement of Mortality (death)
  • Measurement of Morbidity (incidence,
    prevalence)

18
19
Incidence
  • The development of new cases of a disease that
    occur during a specified period of time in
    previously disease-free or condition-free (at
    risk) individuals.

19
20
There are two fundamental approaches to
considering the incidence of disease or a health
condition
- Cumulative Incidence - Incidence
Rate (Incidence Density)
Approaches
20
21
  • Prevalence is another major measure of disease
    in the population
  • It quantifies the burden of disease

Number of existing cases of disease in
population in time period
Prevalence Rate

Persons in population in same time period
21
22
Epidemiology is frequently used in clinical
populations.
  • To identify the response of health problems to
    health care solutions
  • Assess the impact of health care on health
    problems (i.e. does treatment work?)
  • Assist in the development of health services and
    programs

22
23
Health Outcomes
  • May be intermediate in the clinical course of a
    disease or treatment
  • Short-term events
  • May be the end-result of the clinical course of a
    disease or treatment
  • Longer-term events

23
24
Health Outcomes
Related to Prognosis or the Evaluation of Health
Care Interventions
  • Death
  • Recovery
  • Ongoing Disease
  • Stable disease with treatment
  • Progressive disease
  • disability
  • HRQOL health related quality of life
  • Re-infection, Recurrence

24
25
  • Mortality is one of the major measures of
    disease in the population
  • information available from death certificates
    (required by law)
  • Crude
  • Death rate

Number of deaths in time period

Number at risk of dying in period
25
26
  • Infant Mortality Rate assesses the risk of
    dying during the first year of life

Number of deaths under age 1 year in time period

Number of live births in time period
26
27
  • Case-fatality the frequency in which cases of
    disease die
  • Case-fatality rate the proportion of persons who
    die from a disease

Number of deaths among persons with disease

Number of persons with the disease
27
28
  • Years of Potential Life Lost (YPLL) Measure of
    the loss of future productive years resulting
    from a specific cause of death. Indicates the
    potential burden related to when death occurs.
  • YPLL are highest when
  • The cause of mortality is common or relatively
    common, AND
  • Deaths occur at an early age.

28
29
Other Health Outcomes
  • Disability rates
  • Nutrition-related indicators
  • Health Care Utilization rates
  • Indicators of social and mental health

29
Salama
30
Outcome measures in research studies may be
expressed in differing units, though most often
as rates
30
31
Tools of Measurement
Counts Proportions Ratios Rates
31
32
Case Counts
  • Measuring disease or health or health care
    frequency starts with counting cases
  • Simplest and most frequently gathered measure in
    epidemiology

32
33
Counts
Refers to the number of cases of a disease or
other health phenomenon being
studied i.e. Number of cases of influenza in
Astana in January 2012 Can be useful for
allocation of health resources Limited
usefulness for epidemiologic purposes without
knowing size of the source population
33
34
Counts Limited Interpretation
New Cases Location of Disease
Year Population City A 20 2008
100 City B 100 2008
1000 Annual Rate of Occurrence City A 20 / 100
1 / 5 City B 100 / 1000 1 / 10
34
35
Proportions
  • Persons included in the numerator are always
    included in the denominator
  • A
  • Proportion --------
  • A B
  • Indicates the magnitude of a part, related to the
    total. In epidemiology, tells us the fraction of
    the population that is affected.

35
36
Proportions - Example
A B Total (A B)
persons with hypertension persons without hypertension Total study population
1,400 9,650 11,050
P A / (A B) (1,400 / 11,050) 0.127
36
37
Ratios
  • Like a proportion, is a fraction, BUT without a
    specified relationship between the numerator and
    denominator
  • Example Occurrence of Major Depression
  • Female cases 240 240
  • ------------------------ ---- 21 female
    to male
  • Male cases 120 120

37
38
Rates
  • A ratio in which TIME forms part of the
    denominator
  • Epidemiologic rates contain the following
    elements
  • health issue frequency (in the numerator)
  • unit size of population
  • time period during which an event occurs

38
39
  • Rate a measure of the occurrence of a health
    event in a population group at a specified time
    period

Number of events in time period
numerator

denominator
Number at risk for the event in period
39
40
  • Rates are the basic tool of epidemiologic
    practice
  • Why are rates important?
  • because they provide more complete information to
    describe or assess the impact of a health issue
    in a community or population

40
About PowerShow.com