epidemiologi- pendahuluan

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EPIDEMIOLOGI Hari Kusnanto

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Page 1: Epidemiologi- Pendahuluan

EPIDEMIOLOGI Hari Kusnanto

Page 2: Epidemiologi- Pendahuluan

EPIDEMIOLOGI

• Penyakit terjadi karena udara buruk (miasma), ditularkan oleh kuman, akibat kurang gizi

• Apakah risiko kejadian penyakit?

• Epidemiologi dan pentingnya konteks populasi yang diteliti

Page 3: Epidemiologi- Pendahuluan

Kesehatan Individu dan Masyarakat

Treatment

Prevention

Medicine

Health

education

Health

services

research

Public

health

Individu Populasi

Page 4: Epidemiologi- Pendahuluan

Traditional Epidemiology

The study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to control health problems

(Last, 1988)

Page 5: Epidemiologi- Pendahuluan

Introduction

• Germs and miasmas

• Risk factor epidemiology

• Epidemiology in the 21st century

Page 6: Epidemiologi- Pendahuluan

Snow on Cholera

Water Deaths From Death

Supplier Population Cholera Rate

Southwark 167,654 844 5.0 & Vauxhall

Lambeth 19,133 18 0.9

Both 300,149 652 2.2

Page 7: Epidemiologi- Pendahuluan

Snow’s Cholera Map

Page 8: Epidemiologi- Pendahuluan

The Decline in Tuberculosis Death rate

0

50

100

150

200

250

300

1855 1875 1895 1915 1935 1955

Year

De

ath

ra

te

PERUBAHAN

LINGKUNGAN

SOSIAL, FISIK DAN

BIOLOGI

Page 9: Epidemiologi- Pendahuluan

Social and Economic Factors and Health

Just as social changes were the major cause of decline in infectious diseases last century, social changes are also likely to be the most effective means of reducing chronic diseases such as heart disease and cancer.

Page 10: Epidemiologi- Pendahuluan

Chapter 1

Introduction

• Germs and miasmas

• Risk factor epidemiology

• Epidemiology in the 21st century

Page 11: Epidemiologi- Pendahuluan

Epidemiology Is a Population Science

• “Traditional” epidemiology starts at the population level and the first step is to ascertain variations in the occurrence of disease within and between populations

• “Populations” include not only countries, but geographical regions, demographic groups, communities, extended families, etc

Page 12: Epidemiologi- Pendahuluan

Epidemiology Is a Population Science

• Many of the major discoveries in cancer epidemiology followed the publication of “Cancer Incidence in Five Continents” in the 1950s and 1960s which generated new hypotheses about possible (population and individual) causes of cancer

• Of the 30-40 known occupational carcinogens, all were discovered in epidemiological studies and it often took many years of laboratory work to subsequently establish the etiologic mechanism

Page 13: Epidemiologi- Pendahuluan

Examples of the “Top Down” Approach

• Cancer Incidence in Five Continents

• Global comparisons of CDH

• Global comparisons of asthma prevalence

– The European Community Respiratory Health Study (ECRHS)

– The International Study of Asthma and Allergies in Childhood

Page 14: Epidemiologi- Pendahuluan

Levels of Analysis: “Top-down” Versus “Bottom-up”

Populations

Groups

Individuals

Organs

Cells

Molecules

Social science/

epidemiology

Clinical

Pathology/

biology

Molecular biology

Page 15: Epidemiologi- Pendahuluan

The “Top-down” Approach

• Starts at the population level in order to ascertain the main factors that influence health status within the population

• Uses a structural model of causation, rather than a behavioural model or a biomedical model

• Causation is seen as resulting from processes and mechanisms that are internal between externally-related independent objects

Page 16: Epidemiologi- Pendahuluan

“Modern” Epidemiology

“The study of the occurrence of illness”

“A systematic body of epidemiologic principles by which to design and judge [epidemiologic] studies has begun to form only in the last two decades”

(Rothman, 1986)

Page 17: Epidemiologi- Pendahuluan

“Modern Epidemiology”

• Epidemiology is a generic method

• The word “populations” is not necessary for its definition

• The focus is on measuring individual exposure-disease associations

• Certain study designs are most valid

• We should focus on hypotheses that fit these study designs

Page 18: Epidemiologi- Pendahuluan

“Modern” Epidemiology

• Concentrates on studying individual “risk factors” for disease

• “Clinical trial” paradigm comparing “exposed” with “non-exposed” individuals

• Emphasis on “analytical” rather than “descriptive” studies

• Emphasis on individuals rather than populations

• Increasing emphasis on molecular biology

Page 19: Epidemiologi- Pendahuluan

Problems of the Risk Factor Approach: Tobacco

0

10

20

30

40

50

60

70

80

I II IIIN IIIM IV V

Class

%

Ex-smokers

Current smokers

Page 20: Epidemiologi- Pendahuluan

Problems of the Risk Factor Approach: Tobacco

The limited success of legislative measures in industrialised countries has led the tobacco industry to shift its promotional activities to developing countries so that more people are exposed to tobacco smoke than ever before.

Thus, on a global basis the “achievement” of the public health movement has often been to move public health problems from rich countries to poor countries, and from rich populations within the industrialised countries.

Page 21: Epidemiologi- Pendahuluan

Problems of the Risk Factor Approach: Tobacco

When a public health problem is studied in individual terms (eg. tobacco smoking) rather than in population terms (eg. tobacco production, advertising and distribution, and the social and economic influences on consumption) then it is very likely that the solution will also be defined in individual terms and the resulting public health action will merely move the problem rather than solve it.

Page 22: Epidemiologi- Pendahuluan
Page 23: Epidemiologi- Pendahuluan

Problems of the Risk Factor Approach: Asbestos

0

1000

2000

3000

4000

5000

1973 1981 1990

Year

Tonnes (

1,0

00s)

Brazil

Zimbabw e

South Africa

USSR

Canada

Page 24: Epidemiologi- Pendahuluan

Problems of Modern Epidemiology: Biomarkers

“We are in the era of molecular research ... The use of molecular markers represents a quantum leap in the evolution of epidemiologic ideas”

(Schulte, 1993)

Page 25: Epidemiologi- Pendahuluan

Problems of Modern Epidemiology: Scientific Limitations of Biomarkers

• Historical exposures

• Individual temporal variation

• Study size

• What does a biomarker measure?

• Increased likelihood of confounding

Page 26: Epidemiologi- Pendahuluan

Problems of “Modern” Epidemiology

Epidemiology has largely ceased to function as part of a multidisciplinary approach to understanding the causation of disease in populations and has become a set of generic methods for measuring associations of exposure (“risk factors”) and disease in individuals.

If epidemiology is just about measurement then it can never claim to be a science.

Page 27: Epidemiologi- Pendahuluan

Problems of “Modern” Epidemiology

Recent changes in the epidemiologic paradigm have occurred, and have reflected changes in, the way in which epidemiologists think about health and disease.

The key issue has been the shift in the level of analysis from the population to the individual.

Page 28: Epidemiologi- Pendahuluan

Chapter 1

Introduction

• Germs and miasmas

• Risk factor epidemiology

• Epidemiology in the 21st century

Page 29: Epidemiologi- Pendahuluan

Epidemiology in the 21st century

• The importance of context

• Problem-based epidemiology

• Appropriate technology

• Epidemiology as a population science

Page 30: Epidemiologi- Pendahuluan

Context Is Important

The “populations” which epidemiologists study are not just collections of individuals which are conveniently grouped for the purposes of study, but are instead historical entities.

Every population has its own history, culture, organisation, and economic and social divisions which influences how and why people are exposed to particular factors, and how they respond.

Page 31: Epidemiologi- Pendahuluan

Context Is Important

Even when focusing on individual-level hypotheses, epidemiology is inevitably entangled with society and it is unscientific to study disease in the abstract.

To understand the causation of disease in a population it is essential to understand the historical and social context.

The assumption that universal dose-response relationships are the norm arises from the narrow interests and experience of Western epidemiologists.

Page 32: Epidemiologi- Pendahuluan

The Importance of Context

• There were large numbers of deaths amongst the indigenous people when New Zealand (Aotearoa) and other areas of the Pacific were colonised in the 19th century

• It is commonly assumed that these deaths were due to infectious diseases, and affected all populations

• In fact, many populations experienced very few deaths

• The main determinant of death from infectious disease was whether land was taken (and therefore the social systems disrupted)

Page 33: Epidemiologi- Pendahuluan

Problem-based Epidemiology

• The approach of “problem-based” medicine can be used in the teaching and practice of epidemiology

• The appropriate methods should be chosen to fit the problem rather than letting the methods define the problem

Page 34: Epidemiologi- Pendahuluan

Appropriate Technology: theories

• New theories or hypotheses may require new methods of measurement

• As attention moves “upstream” existing epidemiologic methods will become inappropriate

Page 35: Epidemiologi- Pendahuluan

Appropriate technology: methods

• It cannot be simply assumed that high-tech methods such as “molecular epidemiology” will be more valid than traditional questionnaires

• There is a need for an “evidence-based” approach to the teaching and conduct of epidemiology

Page 36: Epidemiologi- Pendahuluan

Appropriate Technology: methods

• Just as case-control studies were developed for “risk factor” epidemiology, new methods need to be developed for “ecoepidemiology”

• We should focus on the important public health issues and use appropriate technology to address them

Page 37: Epidemiologi- Pendahuluan

Appropriate technology: Strategies

• It cannot be simply assumed that a “bottom-up” approach will be more effective, particularly since the “top down” approach has been effective in the past

Page 38: Epidemiologi- Pendahuluan

Epidemiology in the 21st century

• The current danger for epidemiology is not the use of new techniques or micro-level analyses, but that these techniques may define which hypotheses are acceptable for study

Page 39: Epidemiologi- Pendahuluan

All of the Different Levels of Analysis Are Important

• Population level studies are complementary to studies at the individual and micro-levels

• Individual and micro-level studies have had some real successes

• It is legitimate that people should work at the level appropriate to their training and interest

• A multi-level approach may be particularly effective

Page 40: Epidemiologi- Pendahuluan

Epidemiology in the 21st century

Susser suggests that epidemiology has been through three major phases and is now entering a fourth:

• miasma theory epidemiology (“traditional”)

• germ theory epidemiology (“traditional”) • “black box” epidemiology (“modern”, “risk

factor”) • global epidemiology

Page 41: Epidemiologi- Pendahuluan

Epidemiological Paradigms “Traditional”

• Branch of “public health”

• Demography/social science paradigms

• Population level

• Top down (structural, dialectical)

• Intervention “upstream”

“Modern”

• Branch of “science”

• Clinical trial paradigm

• Individual/molecular level

• Bottom up (reductionist positivist)

• Intervention “downstream”

Page 42: Epidemiologi- Pendahuluan

Epidemiology in the 21st century

• We need to reintegrate epidemiology into public health and restore the population perspective

• This requires not just multi-level analysis but rather “multi-level thinking”

• This multi-level thinking can be encouraged and fostered by a problem-based and evidence-based approach