Transcript EPIDEMIOLOGY & ITS USES

EPIDEMIOLOGY ITS PERSPECTIVES
& APPLICATIONS
Dr. A.K.AVASARALA MBBS, M.D.
PROFESSOR & HEAD
DEPT OF COMMUNITY
MEDICINE & EPIDEMIOLOGY
PRATHIMA INSTITUTE OF
MEDICAL SCIENCES,
KARIMNAGAR,A.P..
INDIA : +91505417
[email protected]
EPIDEMIOLOGYPRESENT PERSPECTIVES
•
A PHILOSOPHICAL STUDY OF HEALTH
PROBLEM (SLIDES 3-11)
• AN ART OF THE POSSIBLE (SLIDES 11 - 17)
• A SCIENCE WITH WIDER APPLICATIONS
(SLIDES 18-37)
(OXFORD TEXT BOOK OF PUBLIC HEALTH)
PHILOSOPHICAL STUDY
SLIDES 3 TO 11
EPIDEMIOLOGY
PHILOSOPHICAL
STUDY
OF
HEALTH
PROBLEM
(OXFORD TEXT BOOK OF
PUBLIC HEALTH)
Philosophy is that ill health
is non-randomly distributed
in the nature in clusters
making things easier
to study its various
presentations. It is not
just the methodology of
describing its distribution
and determinants. It is more
than a methodology.
VON KIPPLING ‘S SIX HONEST
SERVING MEN
• WHY ?
• WHAT ?
• WHOM ?
• WHEN ?
• WHERE ?
• HOW ?
• PHILOSOPHICAL
APPROACH
THERE IS NO SITUATION IN
LIVES OF THE PEOPLE
WHERE ONE CANNOT
OBTAIN INFORMATION
EMPLOYING THESE SIX
HONEST MEN WISELY.
THIS IS GENERALIZED
UNIVERSAL
PHILOSOPHICAL LIFE
APPROACH UTILIZED IN
EPIDEMIOLOGY.
EPIDEMIOLOGICAL APPROACH
IS ALSO TYPICALLY PHILOSOPHICAL
THE ONLY WAY TO ASK SOME QUESTIONS
ONE WAY OF ASKING OTHERS
NO WAY AT ALL TO ASK MANY
(MORRIS)
WILLIAM FROST
MOST OF THE TIMES , WE MAY
FIND DIFFICULTY IN KNOWING
THE CAUSE OF ILLNESS INSPITE
• IT IS
OF HAVING LOT OF KNOWN AND
SOMETHING OBSERVED FACTS. THE SECRET
MAY LIE SOMEWHERE IN THE
BEYOND
NATURE (ENVIRONMENT).
THE USUAL
TACT AND SKILL ARE REQUIRED
FACTS OF
TO THINK PHILOSOPHICALLY TO
OBSERVATION
DETECT THIS SECRET. IT IS LIKE
MEDICAL DETECTION AND
NEEDS CREATIVE THINKING AND
GENIUS LIKE SHERLOCK
HOLMES.
EPIDEMIOLOGY IS APPLIED COMMON
SENSE (BRETT & CASSENS )
COMMON SENSE MUST ALWAYS PREVAIL
IN EPIDEMIOLOGICAL DEALINGS.
IT IS AN INTELLIGENT WAY OF STUDYING
HEALTH PROBLEM AND NEEDS COMMONSENSE.
SINCE DISEASES USUALLY OCCUR IN
CLUSTERS AND IN CERTAIN PLACES, WE
APPLY COMMON SENSE IN SEARCHING
FOR THEIR CAUSES
IF CAUSE IS NOT SECURED, WE SEARCH
FOR RISK FACTORS.
PERSONAL EXPERIENCE
AN EXAMPLE FOR TIMELY COMMONSENSE
SOMETIMES PLACE DISTRIBUTION ALSO GIVES
CLUES ABOUT A DISEASE
A PERSONAL EXPERIENCE OF MINE WHILE
INVESTIGATING MALARIA EPIDEMIC OF 40 FEVER
CASES AND 11 DEATHS IN A VILLAGE NEAR
VISAKHAPATNAM STEEL PLANT SERVES AS AN
EXAMPLE.
SIX CHILDREN WITH ENLARGED SPLEENS AND
FEVER FOUND THERE ARE EXPECTED TO BE
SUFFERING FROM MALRIA. BUT AFTER SEEING
THE ADDRESS OF ONE CHILD WHO CAME FROM
WEST BENGAL, INDIA WHICH IS ENDEMIC FOR
VISCERAL LEISHMANIASIS, A DOUBT CAME TO MY
MIND THAT WHY IT COULD NOT BE KALA AZAR.
PAST PERSPECTIVES
• 1873 – PERKINS – TREATMENT OF EPIDEMICS.
• 1927 – W.H. FROST – MASS PHENOMENON OF
INFECTIOUS DISEASE.
• 1934 – MASS PHENOMENON OF ANY DISEASE.
EPIDEMIOLOGY DESCRIBES
FURNITURE OF EARTH
GOOD DEAL OF EPIDEMIOLOGY HAS A
LITTLE TO DO WITH THE TESTING OR
REFUTATION OF HYPOTHESIS BUT IS
CONCERNED WITH THE DESCRIBING
WHAT HAS BEEN CALLED THE
“FURNITURE OF EARTH”
STEBBING LS, PHILOSOPHY AND THE PHYSISTS,
2ND EDITION, NEWYORK DOVEV, 1958 CHAPTER III
IT IS AN ART
SLIDES 12 TO 19
ART OF EPIDEMIOLOGY
• SKILLS OF APPROPRIATENESS,
CREATIVITY & INNOVATION
ARE ESSENTIAL.
• IT IS THESE ESSENTIAL SKILLS THAT
MAKES EPIDEMIOLOGY MORE
THAN A METHODLOGY
EPIDEMIOLOGICAL STUDY SHOULD BE
LIKE MOTHER’ S TASTY FOOD
EVERYONE CAN PROCURE ALL
THE NICE FOOD ITEMS AND
CAN ALSO LEARN VARIOUS
COOKING METHODS BUT
CANNOT MAKE A TASTY FOOD
LIKE MOTHER BECAUSE
MOTHER SELECTS THE RIGHT
FOOD ITEMS
(APPROPRIATENESS)YOU LIKE
AND COOK THEM IN THE
CORRECT WAY YOU ENJOY
AND SERVES YOU WITH
AFFECTION.
CREATIVITY & INNOVATION
•THAT TYPE OF ART IS ESSENTIAL IN
MAKING A EPIDEMIOLOGICAL STUDY
SUCCEESSFUL AND PLEASING(TASTY)
TO THE NEEDY.
•IT IS JUST NOT ENOUGH TO KNOW
VARIOUS EPIDEMIOLOGICAL METHODS.
•ONE MUST APPLY THEM CREATIVELY TO
OBTAIN THE INFORMATION NEEDED TO
UNDERSTAND THE NATURAL HISTORY OF
DIEASE.
ART OF EPIDEMIOLOGY
ART OF
CAUSES
HEALTH
LINKING
CAUSES,
CONDITIONS &
&
LINKING
FACTORS WITH
HEALTH AND CONDITIONS
DISEASE
DISEASE OF
POPULATION
OF
FACTORS
POPULATIONS
• ART OF EXTRAPOLATING TWO TRIADS
TO EXPLAIN VARIOUS INTERACTIONS
TIME
AGENT
HOST
PLACE
ENVIRONMENT
PERSON
ART OF THE POSSIBLE
 NOTHING CAN BE PROVED OR
ESTABLISHED 100% AS IN LABORATORY
EXPERTIMENT AS IT IS POPULATION
BASED.
 ONLY MAXIMUM PROBABILITY CAN BE
TRIED.
 SO ONE SHOULD BE MODEST AND
REALISTIC AND KNOW THE LIMITATIONS
WHILE CARRYING OUT THE
EPIDEMIOLOGICAL STUDIES.
ART OF POSSIBLE
• ALL THE FRUITS OF SCIENTIFIC WORK,
IN EPIDEMIOLOGICAL OR OTHER
DISCIPLINES, ARE AT BEST ONLY THE
TENTATIVE FORMULATIONS OF A
DISCRIPTION OF NATURE.
• THIS TENTATIVENESS OF OUR
KNOWLEDGE DOES NOT PREVENT
PRACTICAL APPLICATIONS BUT SHOULD
KEEP US SCEPTICAL AND CRITICAL,
NOT ONLY OF EVERYONE ELSE’S WORK,
BUT OUR OWN AS WELL
(OXFORD TEXT BOOK OF PUBLIC HEALTH)
A SCIENCE
SLIDES 20-41
A SCIENCE
• IT FOLLOWS ALL THE BASIC TENETS
OF SCIENCE
• IT HAS AN ORDER AND DEFINITE
PURPOSE
• IT HAS SEQUENCE, RELAVANCE,
INFERENCE AND IS SYSTEMATIC
• IT FOLLOWS ETHICS
• IT HAS WIDER & ACCEPTABLE
APPLICATIONS
EPIDEMIOLOGY IS BOTH THE
BASIC SCIENCE OF PUBLIC
HEALTH AND ITS MOST
FUNDAMENTAL PRACTICE
MAXCY
LANGMUIR ON EPIDEMIOLOGICAL
PRACTICE
SURVILLANCE,
EPIDEMIOLOGICAL
INVESTIGATIONS
COUNT CASES &
MEASURE THE
POPULATION
AFFECTED
RESULTING
INFORMATION
APPLIED FOR
PREVENTION &
CONTROL
DISSEMINATION
TO HELATH
PLANNERS &
PUBLIC
EVALUATION
DETECTS,
INVESTIGATES
& ANALYZES
PROBLEMS
HEALTH
PROGRAMS
HEALTH
POLICY
OBJECTIVES OF EPIDEMIOLOGY
AIM
OF
EPIDEMIOLOGY
H
E
A
FOR
L
T
TAKING H
A
C
TI
O
N
DISEASE LOAD
CAUSE
EDUCATION AL
& RESEARCH
RIGHT HAND OF COMMUNITY
MEDICINE
COMMUNITY MEDICINE
EPIDEMIOLOGY
BIOSTATISTICS
EPIDEMILOGY PROVIDES
INTELLIGENCE
FOR HEALTH ACTION
INTELLIGENCE MEANS
INFORMATION REGARDING
THE DETERMINANTS OF HEALTH &
DISEASE AND THEIR OCCURRENCE &
MAGNITUDE IN POPULATIONS
FOR TAKING HEALTH ACTION
J. N. MORRIS
EPIDEMIOLOGICAL PURPOSE &
SEQUENCE
1. IDENTIFYING DISEASE/ HEALTH PROBLEM
2. LINKING WITH THE CAUSE / RISK
FACTORS
3. ESTABLISHING CAUSAL RELATION- SHIP
4. DESIGNING AN INTERVENTION FOR
CONTROLLING PROBLEM
5. TO EVALUATE THE EFFECTIVENESS OF
INTERVENTION
(MAXCY)
MORRIS’ SEVEN USES
1.
2.
3.
4.
TREND STUDY
COMMUNITY DIAGNOSIS
HEALTH SERVICES EVALUATION
TO KNOW THE INDIVIDUAL RISKS AND
CHANCES
5. SYNDROME IDENTIFICATION
6. COMPLETING THE CLINICAL PICTURE
7. SEARCHING FOR CAUSES / RISK
FACTORS FOR ESTABLISHING CAUSAL
RELATIONSHIP
TREND STUDY
1. STUDYING THE PAST HISTORY FOR
RISE AND FALL
2. STUDYING ITS CHANGING BEHAVIOUR
3. MAKING FUTURE PREDICTIONS
4. GIVING EARLY WARNINGS OR FEED BACK
COMMUNITY DIAGNOSIS
SOCIAL
ANATOMY
SOCIAL
PHYSIOLOGY
SOCIAL
PATHOLOGY
COMMUNITY
DIAGNOSIS
QUALITATIVE
ESTIMATION
QUANTIFICATION
COMMUNITY DIAGNOSIS
1. SOCIAL ANATOMY: RACE, AGE AND
SEX COMPOSITION, SOCIO ECONOMIC
STATUS, POPULATION AT RISK,
RESOURCES AVALAIBLE.
2. SOCIAL PHYSIOLOGY: POSITIVE
&NEGATIVE LIFESTYLES, OCCUPATION,
HEALTH SERVICES AWARENESS AND
UILIZATION, NUTRITIONAL POLICES,
LABOUR.
3. SOCIAL PATHOLOGY:
MORBIDITY,
MORTALITY, DISABILITY, ALCHOLISM,
SMOKING, CRIME & VOILENCE, RISK
PRONE BEHAVIOUR.
COMMUNITY DIAGNOSIS
MUST BE DYANAMIC
IN A WORLD OF CHANGE,
EPIDEMIOLOGIST HAVE A SPECIAL
DUTY TO OBSERVE THE IMPACT “UPON
THE PEOPLE” AND THE WAY WE LIVE TO
DIAGNOSE WHERE WELL -BEING IS
INCREASING AND WHERE LOSING OUT,
TO PROBE FOR UNINTENDED
CONSEQUENCES , TO IDENTIFY TRENDS
AND TO THINK AHEAD.
ONION PRINCIPLE
JUST LIKE THE LAYERS OF
THE ONION, THE OLD
DISEASES WANE AND GIVE
PLACE TO NEWONES.
INFECTIOUS ONES WILL BE
REPLACED BY NON–
INFECTIOUS ONES TO BE
REPLACED LATERBY
PERSONAL AND
BEHAVIORAL PROBLEMS.
ONE MUST BE AWARE OF
THIS PHENOMENON
BEFORE DIAGNOSING THE
OLD DISEASES
COMMUNITY HEALTH
HEALTH SERVICES
EVALUATION
•
•
•
•
HEALTH PLANNING FOR
APPROPRIATE
COST EFFECTIVE
COMMUNITY NEED BASED
JUDICIAL MIX OF PREVENTIVE,
PROMOTIVE, CURATIVE,
REHABILITATIVE AND PUBLIC HEALTH
SERVICES
SYNDROME IDENTIFICATION
LUMPERS
&
SPLITTERS
GROUPING AND DIVIDING THE
SYMPTOM- COMPLEXES AND NAMING
THEM AS SYNDROMES IS THE
STARTING POINT FOR THE STUDY OF
NATURAL HISTORY OF ANY DISEASE
SEARCH FOR CAUSES
SEVERAL CAUSES SINGLE DISEASE
SINGLE CAUSE  SEVERAL DISEASES
SEARCH FOR CAUSE IN INTERRELATED
DISEASES MAY YIELD CLUES FOR NEW
CAUSES / RISK FACTORS
COMPLETING THE CLINICAL PICTURE
OF DISEASE
IN BREADTH
• HOSPITAL STUDIES HAS TO BE BROADEND WITH
SIMULTANEOUS COMMUNITY STUDIES AS THEY
POORLY REPRESENT THE HELTH EVENT IN GENERAL
POPULATION. MERE DEPENDENCE ON STUDIES
CONDUCTED IN HOSPITAL OR ANY HEALTH FACILITY
SETTING IS BIASED BECAUSE THEY DO NOT INCLUDE
THE PREPATHOGENIC AND FOLLOW-UP PHAGES OF THE
DISEASE STUDIED.
IN DEPTH
• GOING TO THE BOTTOM, THE DEEEPER PART OF THE
ICEBERGH TO STUDY THE EARLIER PART OF DISEASE,
WHICH IS EITHER STOPPABLE OR ATLEAST
PREVBENTABLE BY SEARCHING FOR
•
•
•
•
•
•
PRECURSORS OF THE DISEASE
DISPOITIONS DUE TO DISEASE
ASYMPTOMATIC DISEASE
SUBCLINICAL CASES
LATENT CASES
CARRIER STATE
NATURAL HISTORY OF DISEASE
RISK ASSESMENT
INDIVIDUAL RISK
GENERAL POPUTLATION RISK
PROGNOSIS FOR BY PHYSICIAN
CYCLE OF EXTENSION
DISEASE
IN MAN
TB
MAN
INFLUENCING
ENVIRONMENT
SCOPE AND JURISDICTION
STRICTLY SPEAKING, THERE IS NO LIFE
SCIENCE, WHERE EPIDEMIOLOGICAL
APPROACH AND PRINCIPLES CANNOT
BE APPLIED
FROM WOMB TO TOMB EPIDEMIOLOGY IS
APPLICABLE
PREVENTIVE PAEDIATRICS
PREVENTIVE GERIATRICS
PREVENTIVE CARDIOLOGY
CLINICAL EPIDEMIOLOGY