materi analitik - kuliah s2 kesmas
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ANALYTICAL EPIDEMIOLOGY
GENTA JAGAD
EPIDEMIOLOGICAL RESEARCH
Epidemiological research is a study of the distribution and
determinants of health-related states or events in spesified of
populations, and the application of the study to control health
problems.
“STUDY”
Surveillance (pengawasan) Observation (pegamatan) Hypothesis testing (uji
hipotesis) Analytic research (penelitian
analisis) Experimental research
(penelitian dengan perlakuan)
“DISTRIBUTION”
refers to analysis by time,
place and class of person affected.
“DETERMINANTS”
Are all the: Physical (fisik/badan) Biological
(hayati/kehidupan) Social (sosial) Cross-cultural (lintas
budaya) Behavioural factors
(perilaku)that influence
health
HEALTH RELATED STATES and EVENTS
Include Diseases (penyakit) Causes of death (penyebab
kematian) Behaviours such as
(perilaku/kebiasaan) - Use of tobacco- Reactions to
preventative regimens and provision- Use of health services
“SPECIFIED POPULATIONS”
are those with identifeable characteristic such as
precisely defined numbers
“APLICATON OF STUDY TO CONTROL HEALTH PROBLEMS”
Makes explicit the aim of epidemiology:
To promote (meningkatkan) To protect
(melindungi/memelihara) To restore
(memulihkan/menyempurnakan/memperbaharui)
HEALTH
TUJUAN EPIDEMIOLOGI
Mendiskripsikan distribusi, kecenderungan, dan riwayat alamiah penyakit
Menjelaskan etiologi penyakit Meramalkan kejadian
penyakit Mengendalikan distribusi
penyakit.
EPIDEMIOLOGY
DESCRIPTIVE EPIDEMIOLOGY (provides the what, who, when and where)
ANALYTICAL EPIDEMIOLOGY
(attemps to provide the why and how)
DESCRIPTIVE STUDY
Does not try to quantity the relationship Give us a picture what is happening in a
population (e.g. prevalence, incidence, or experience of a group)
It can be case report, case series, qualitative study or surveys which measure the frequency of several factors, and hence
the size of the problem. Sometimes also include analytic work
(comparing factors)
Distribution Tendency Impact
ANALYSE or ANSWER the PRESENT PROBLEM at that time
What
Who
When
Where
ANALYTICAL EPIDEMIOLOGY
Why and How
PROGRAMPOLICY DECISION
DESCRIPTIVE EPIDEMIOLOGY
Schema for an Epidemiologic Study CycleDescriptive studies (data aggregation and analysis)
Formulation of
hypotheses
Analytic studies (to test hypotheses)
1. Analysis of results
2. Suggests further descriptive studies
3. New hypotheses
STUDY DESIGN in ANALYTICAL STUDIES
Treatment studies (experimental studies)
Observational studies
Other terms
EXPERIMENTAL versus OBSERVATIONAL STUDIES
In experiment, the investigator studies the impact of varying some
that he controls.
In observational study, the investigator can only observe the
occurrence of disease in people who are already separated into groups
determined by exposure.
TREATMENT STUDIESRandomized controlled studies Double-blind randomized trial Single-blind randomized trial Non-blind trial
Nonrandomized trial Interupted time series design
(measures on a sample or a series of sample from the same population are obtained several times before and after a manipulated event or a naturaly occuring event) – considered a type of quasi-experiment.
OBSERVATIONAL STUDIESCohort study Prospective cohort Retrospective cohort Time series study
Case-control study Nested case-control study
Cross-sectional study Community survey (a type of
cross-sectional study)
OTHER TERMS Retrospective
study Superiority trials Non-inferiority
trials Equivalence trials Crosover study Longitudinal study Meta-analysis Design of
experimental
Epidemiology triangle
environment
agent host
Interaction between
host and
environment
Inte
ract
ion
betw
een
agen
t and
en
viron
men
t
Interaction between host and agent
Goals of All Analytic Studies
Maximize internal validity (keabsahan)
Maximize external validity Maximize precision
(ketelitian)
ANALYTICAL EPIDEMIOLOGY
Bidang epidemiologi yang dirancang untuk mempelajari paparan:
Faktor risiko Kausa Faktor-faktor yang
dihipotesiskan mempunyai hubungan dengan penyakit.
Outline of the Process of an Epidemiological Study
Establish that a Problem exists
Confirm the Homogeneity of the Events
Collect all the Events Charactherize the events as to
epidemiological factors- Predisposing Fs- Enabling/disabling Fs- Precipitation Fs- Reinforcing Fs
Look for patterns and trends Formulate of a Hypothesis Test of Hypothesis Publish the result
STUDY DESIGN
STUDY DESIGN
- is more important than the analysis
- a badly designed study can never be retrieved
- whereas a poorly analysed one can usually be reanalysed
- consideration of design is also important, because the design of study will govern how
the data are to be analysed.
STUDY DESIGN (rancangan penelitian)All Studies
Descriptive (PO) Analytic (PICO or PECO)
Survey (cross sectional) Qualitative Experimental Observational
(analytic)
Randomised (paralel group)
Randomiised (crossover)
Cohort study
Cross sectional(analytic)
Case-control study Figure: Tree of different types of studies
CROSS - SECTIONAL STUDY
CROSS-SECTIONSL STUDY
DESCRIPTIVE
ANALYTIC
OBSERVATIONAL
ANALYSE or ANSWER the PRESENT
PROBLEM at that time
In observational study the investigator can only observe
the occurrence of disease in people who are already separated into groups determined by exposure.
MEMPELAJARI GAMBARAN/DISKRIPSI:
Distribusi Kecenderungan Dampak penyakit
CROSS SECTIONAL STUDY
Study that examines the relationship between diseases (or other health-related characteristics) and other variables of interest as they exist in a
defined population at one particular time (ie exposure and outcomes are both measured at
the same time).
Best for quantifying the prevalence of a disease or risk factor, and for quantifying the accuracy of a
diagnostic test.
Cross-secional study
Is a descriptive study in which desease and exposure status are measured simultaneously
in a given population.
Can be thought of as providing a “snapshot” of the frequency and characteristics of a desease
in a population at a particular point in time.
The type of data can be used to assess the prevalence of the acute or chronic condition in
a population.
DATA COLECTIONDEFINED
POPULATION
Expose Have
Disease
Expose Do Not Have
Disease
Not Expose Have
Disease
Not Expose Do Not Have
Disease
GATHER DATA on EXPOSUR and DESEASE
Begin with
Data is usually collected through a survey. A population of interest in queried on a variety of possible exposures and on a variety of diseases.
For each exposure and each disease, there are four possible outcomes. These four groups can be compared to suggest possible relations between exposure and disease.
Odds ratios, or various statistical methods such as correlation analysis can be used to compare groups.
ADVANTAGES & DISADVANTAGES OF the DESIGN
ADVANTAGES Cheap and simple; Ethically safe.
DISADVANTAGES Establishes association at most, not casuality; Recal bias susceptibility; Confounders may be unequally distributed; Neyman bias; Group sizes may be unequal.
CASE - CONTROL STUDY
CASE-CONTROL STUDY Sometime referred to as retrospective study,
differs substantially from a cohort study in that the participants are selected on disease status, not on exposure.
Patients with a certain outcome or disease and an appropiate group of controls without the outcome or disease are selected (usually with careful consideration of appropiate choice of controls, matching, ect) and than information is obtained on whether the subjects have been exposed to the factor under investigation.
Design of a Case-Control Study
CASES
DISEASES
CONTROLS
NODISEASES
EXPOSED NOTEXPOSED
NOTEXPOSEDEXPOSED
Once the cases and control have been selected, the investigator collects information from interviews, employment records, and medical records to
determine possible types of exposures
When Are Case-Control Studies Particularly
Valuable? Rare disease Multiple exposures of
interest Budget is tight Particularly useful for
evaluating a bioterrorist attact
ADVANTAGES Quick and cheap; Only feasible method for very rare disorders
or those with long lag between exposure and outcome;
Fewer subjects needed than cross-sectional studies
DISADVANTAGES Reliance of recall or records to to determine
exposure status; Confounders; Selection of control groups is difficult; Potential bias: recall, selection.
ADVANTAGES & DISADVANTAGES OF the
DESIGN