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