EPIDEMIOLOGY INTRODUCTION by Dr. Anuj.ppt

EPIDEMIOLOGY INTRODUCTION by Dr. Anuj.ppt

1. Dr. AnujSingh
Asst. Professor
Community Medicine Dept.
UIMS, Prayagraj

5. H I S T O R Y-
TheGreekphysicianHippocratesisusually
saidtobefatherofepidemiology.Thefirst
persontohaveexaminedtherelationship
betweenoccurrenceofdiseaseandtheir
environmentalinfluences;coinedtheterms
epidemicandendemic.

6. -Dr. John Snowis famous for
the suppression of an 1854
Cholera outbreak in
London’s Golden-square
district.
-He identified the cause of
the out-break as a public
water pump and had the
handle removed, there by
ending the out-break.

7. •FATHEROFMODERNEPIDEMIOLOGY

8. Epidemiology-
Def-
“Thestudyoftheoccurrenceanddistributionof
healthrelatedstatesoreventsandprocessin
specifiedpopulations,includingthestudyofthe
determinantsinfluencingsuchprocess,andthe
applicationofthisknowledgetothecontrolof
healthproblems”
by: John M. Last (1988)

9. Aim of Epidemiology:
Theoverallaimofepidemiologyistoobtain,
interpretandusehealthinformationtopromote,
protectsandrestorehealth;toreduceorremove
diseases;andtoadvancescientificknowledgeto
addresstheabovementionedpurposes.

10. Objective of Epidemiology:
Toundertake“studies”usingoneofthevarious
epidemiologicalmethodsasobservationalor
experimentaldesignsundertakenon“health-related
events,states,andprocesses”includingepidemic
outbreaks,diseases,disorders,causesofdeath,
behaviors,environmentalandsocioeconomic
processes,effectsofpreventiveprograms,anduse
ofhealthservices

11. Objective of Epidemiology : cont..
Todescribethe“distribution,”i.e.,theanalysisof
factscollectedfromthe“study”accordingto
person,place,andtime
Toworkoutthe“determinants,”suchasvarious
physical, biological,behavioral, and
socioeconomicfactorsthatinfluencehealth
Toapplytheknowledgegainedfromtheabove-
mentionedobjectives;topromote,protect,and
restorehealth;andtoadvancescientific
knowledge

12. HowEpidemiologyCaninitiatePublicHealthActionEven
BeforetheActual“CauseisKnown-
1768,EdwardJennershowedthatvariolationcanprevent
smallpox
1747,JamesLindshowedthatlimejuicecanpreventscurvy
Mid-nineteenthcentury,Semmelweis,showedthatwashing
handsbymedicalstudentswasprotectiveagainst
developmentofpuerperalinfectionamongfemalepatients
1848–1854,JohnSnowshowedthatcholeraistransmittedby
contaminatedwater
Earlytwentiethcentury,GoldbergerandFletcherrespectively
showedthatpellagraandBeriberiwerecausedbymaize
dietandpolishedrice,respectively
Mid-twentiethcentury,DollandHill,basedoncase–control
studies,showedthatsmokingcauseslungcancer

13. Principles of Epidemiology:
6 basic principles of epidemiology is to
define epidemiologic event in terms of-
6Ws-
WHAT?
WHO?
WHEN?
WHERE?
WHY?
So what?

14. Principles of Epidemiology: cont..
What:Definethediseasesorhealthevent,
countthecasesorhealthevents,andthereafter
dividetheno.ofcasesbyanappropriate
denominatortocalculaterate

15. Principles of Epidemiology: cont..
Describe the rate so calculated in terms of-
-Who: Person
-When: Time
-Where: Place

16. Principles of Epidemiology: cont..
Why (or how): Compare these rate over
time or for different groups of people and
conclude as to why the rates are different.

17. Principles of Epidemiology: cont..
So what: Apply so conclusion so drawn in
the form of a clinical or public health policy

18. Fundamental concepts
in Epidemiology

19. Five cardinal concepts in epidemiology-
1Cause,prevention,andtreatmentofhealthproblemtobe
identified
2Dataregardingthecauses,prevention,andmanagementof
healthproblemsshouldbequantifiedandanalyzed
3Informationshouldbecollectedfromlargepopulation
4Causalassociationregardingthecauses,preventionand
mgmt.ofhumandiseases/healthproblemscanbe
ascertainedbyobservationalorexperimentalmethod
5Applicationofepidemiologicalresearchshouldbesuitably
usedtobringaboutpolicychange,whetherforpublic
healthorinclinicalpractice.

20. Five cardinal concepts in epidemiology-
1
Cause,prevention,andtreatmentofhealthproblem
tobeidentified-
Healthproblemsandtheirpreventioncanbe
achievedbythestudyofpopulationusing
scientificmethod

21. Five cardinal concepts in epidemiology-
2Dataregardingthecauses,prevention,and
management ofhealthproblemsshouldbe
quantifiedandanalyzed-
Epidemiologyisaquantitativesciencebasedon
sameclinicalmethodsasareusedinmedical
practice
Additionally,itinvolvesprobability,statistics,
sociobehavioralsciencesandsoundresearch
methods.

22. Five cardinal concepts in epidemiology-
3Informationshouldbecollectedfromlarge
population-
Epidemiologyfocusesonalargegroupofpeople
whomaybehealthyordiseased.

23. Five cardinal concepts in epidemiology-
4Causalassociationregardingthecauses,
preventionandmgmt.ofhumandiseases/health
problemscanbeascertainedbyobservationalor
experimentalmethod-
Hypothesis
generation
Hypothesis
testing
Hypothesis
confirmation

24. Five cardinal concepts in epidemiology-
5Applicationofepidemiologicalresearchshouldbesuitably
usedtobringaboutpolicychange,whetherforpublic
healthorinclinicalpractice.

25. Clinical medicine Vs Epidemiology
In Clinical Medicine, the unit of
study is a “Case” or “Cases”.
In Epidemiology,the unit of the
study is “Defined population” or
“Population at risk”.
In Clinical Medicine a Physician
is concerned with the individual
patient who is diseased.
The Epidemiologist’sconcern are
the disease patterns in the entire
population. (both the sick &
healthy)

26. Clinical medicine Vs Epidemiology
InClinicalMedicine,thePatient
comestotheDoctor.
InEpidemiology,theInvestigator
goesoutintothecommunityto
findpersonswhohavethediseases
orexperienceofsuspectedcasual
factorsinquestion.

27. HOWEVER, CLINICAL MEDICINE & EPIDEMIOLOGY
ARE NOT ANTAGONISTIC.
MostEpidemiologicalenquiriescouldnever
beestablishedwithoutappropriateclinical
considerationastohowadiseaseinquestion
canbeidentifiedamongtheindividualsinthe
groupsunderscrutiny.
Likewise,aknowledgeofprevalence,etiology
&prognosisderivedfromtheEpidemiological
researchisveryimportanttoaClinicianforthe
diagnosis&managementofindividualpatients.

28. Uses of Epidemiology

29. USESOFEPIDEMIOLOGY

30. Usesof Epidemiology-
1Healthcaremgmt.
2Understandingthediseaseprocess
3Publichealthpractice
4Clinicalandindividualizespreventivepractice

31. Usesof Epidemiology-
1.Makingacommunitydiagnosis:
Inclinicalsettings,theclinicianmakesaclinical
diagnosis.
Inhealthcareofalargecommunity,thehealth
providermustmakea“communitydiagnosis.”By
epidemiologicalmethodstoobtaininformationonthe
importanthealthproblemsandtheirassociated
socio-demographiccharacteristics,quantifyingand
summarizingthem.
Oncea“communitydiagnosis”hasbeenmade,we
candecideastowhichprogramswouldbebestfor
improvingthehealthstatusofacommunity

32. Usesof Epidemiology-
2.Planningandevaluationofhealthservices:
Anyplanningprocesswillneedaccurateinformation
aboutthesocio-demographicprofile,diseases,healthcare
facilities,communications,etc.
Similarly,whileevaluatingahealthprogram,wewillagain
needcurrentinformationaboutvariousdiseasesand
compareitwiththe“baseline”statethatexistedwhenwe
startedtheprogram.
Thisquantifiedandsummarizedinformationisavailable
onlythroughepidemiology.

33. Usesof Epidemiology-
3.Developinghealthpolicies:
Epidemiologyisindispensableformakingassessmentof
community“diagnosis”and“needs.”
Inaddition,itprovides“evidence-based”decisionsabout
theriskstotheindividualsandcommunitiesdueto
variousexposures.
Thesetwofactsmakeitakeydisciplinefordeveloping
publichealthpolicies.

34. Usesof Epidemiology-
4.Studyofthenaturalhistoryofdiseases:
WhatweknowtodayofthenaturalcourseofHIVor
pulmonaryTBoranyotherhumandiseasehasbeenmade
possiblebysystematicobservationsonhundredsand
thousandsofpatientsanddescriptionofthesummarized
findingsfromtheseobservationsonthelargenumberof
patients,whichispossibleonlybyepidemiological
methods.

35. Usesof Epidemiology-
5.Searchingforthecausesandriskfactorsofdiseases:
HowdowesaythatsmokingisacauseofIHD?Orobesity
isariskfactorfordiabetes?Itisbyobservingthousands
ofobeseandnon-obesepeopleandfollowingthemtosee
whatpercentageineachgroupdevelopsdiabetes(cohort
epidemiologicalapproach)orelsebyaskinghundredsof
IHDpeoplecomparedtohundredsofhealthypeopleabout
theirsmokinghistory(case–controlepidemiological
approach).

36. Usesof Epidemiology-
6.Historicstudyofriseandfallofdiseases:
Smallpoxrosetoitspeak,killedmillions,andwasfinally
eradicated;plaguealmostvanishedafterkillingahuge
proportionofhumanityandthenreappeared.Epidemiological
studiesofsuchriseandfallofdiseasesareessentialto
understandthevariousfactorsthatcanbeeffectivelyutilized
inpreventingtheoccurrenceorre-emergenceofother
diseases.

37. Usesof Epidemiology-
7.Toidentifysyndromes:
A“syndrome”meanssimultaneousoccurrenceoftwoor
moredifferentmedicalphenomena (constellationsof
signs/symptoms)morefrequentlythanwhatcanbe
accountedforbysimplya“chance”association.Itisonly
afterobtainingdataonhundredsofpatientsfromvarious
countriesaboutsignsandsymptomsofarelatednature,
throughepidemiologicalmethods,thatweareabletoputthe
piecesofinformationtogetherandidentify“syndromes”and
theiretiologicalfactors.E.g.,theinitialsingleentity,“peptic
ulcer”wasdistinguishedastwoentities(duodenalandpeptic
ulcer).

38. Usesof Epidemiology-
8.Investigations of epidemics and other field
investigations:
Epidemiology originally started as a science dealing
with investigations of epidemics; even now, it remains
one of its most important aims.
9.Surveillance for diseases:
In addition to the investigation of epidemics, disease
surveillance is another important function for which
epidemiology came into being. Surveillance
essentially monitors trends in the occurrence of
selected diseases, thereby giving early warning about

39. Usesof Epidemiology-
10.Makingprojections:
Quiteoften,wehearthattherewillbesomanymillion
casesofIHDinacountryby2025andsoon!These
projectionsaremadeonthebasisofmathematicalmodels
developedbyepidemiologistsaftercollectingdatafrom
largepopulationsforthepastmanyyears.
11.Assessingtheprogramsformassscreeningfor
diseases:
Basedonepidemiologicalprinciplesof“diagnostictest
assessment,”themassscreeningprogramsareplanned
andsubsequentlyevaluatedfortheireffectivenessinlarge
populationgroups.