1. BY DR. SNEHAL KASARE MODERATOR: DR. RAMESH PAWAR
USES OF EPIDEMIOLOGY
BY DR. SNEHAL KASARE
MODERATOR: DR. RAMESH PAWAR

2. FRAME WORK INTRODUCTION OF EPIDEMIOLOGY DEFINITIONS
AIMS OF EPIDEMIOLOGY
USES OF EPIDEMIOLOGY

3. INTRODUCTION OF EPIDEMIOLOGY
(Greek; Epi = upon, Demos = populations, Logos = scientific study).
Epidemiology is the basic science of preventive and social medicine.
The major purpose of epidemiology is to obtain, interpret and use health information to promote health and reduce disease in a community.
It has evolved rapidly in past few decades.
It covers disease distribution, causation and prevention as well as health and health related events occurring in human population

4. Ctd. introduction “JOHN SNOW” FATHER OF MODERN EPIDEMIOLOGY
Modern epidemiology helped in
Identifying risk factors of chronic disease
Evaluating treatment modalities and health services
Provides new opportunities for prevention and planning
Improving the effectiveness and efficiency of health services

5. John Snow contribution
1854 john snow who methodically covered the street of London collecting statistics documenting the location of outbreak. Snow identified that contaminated water from communal pumps is the source of cholera

6. This pump was later suspected and proved to be a source of infection
Study by John Snow, 1854
Spot map of deaths from cholera in Golden Square area, London, 1854
This pump was later suspected and proved to be a source of infection

7. John memorial and public house on broadwick street, Soho

8. Definitions Of Epidemiology
“That branch of medical science which treats of epidemics”(Parkin,1873)
“The science of disease of the mass phenomena of infectious disease” (Frost,1927)
“The study of the distribution and determinants of disease frequency in man”(MacMohan,1960)

9. “The study of the distribution and determinants of
health-related states or events in the specified
populations, and the application of this study to the
control of health problems”.
( JOHN M LAST 1988)

10. International Epidemiological Association (IEA) three aim of epidemiology
To describe the distribution and size of disease problems in human populations.
To provide the data essential to planning, implementation and evaluation of service for the prevention, control and treatment of disease and to the setting up of priorities among the services.
To identify etiological factors in the pathogenesis of disease.

11. The Clinician & the Epidemiologist
Patient
Person
Population
Monitor health
Periodic exam
Surveillance
When the patient gets sick
Diagnose & treat
Investigate & recommend interventions
Follow-up
Return visit
Program evaluation
Research
Clinical study or trial
Epidemiological study

12. Uses of Epidemiology
1) Community Diagnosis 2) Planning and Evaluation 3) Natural History of disease 4) To study historically the rise and fall of disease in population 5)Syndrome Identification 6) Searching for causes and risk factors 7) To measure risk

13. Community Diagnosis
It referrs to the identifications and quantification of health problems in a community in terms of mortality and morbidity rates and ratios
Identification gives the purpose of defining those individuals or groups at risk or those in need of health care
Quantification 1) Lay down the priorities in disease control and prevention 2) Source of new knowledge of disease distribution, causation and prevention.

14. STEPS FOR COMMUNITY DIAGNOSIS
Step 1 - Establishing a Community Diagnosis Team
Step 2 - Analyzing the existing Health Data
Step 3 - Collecting Community Data
Step 4 - Combining existing Health Statistics With
Community Data
Step 5 - Choosing Health Priorities
Step 6 - Developing the Community Health Action Plan
Step 7 - Measuring Environmental and Policy Changes
Step 8 - Creating the Community Diagnosis Document

15. Planning And Evaluation
Planning is essential for rational allocation of limited source
Planning includes facilities for medical care(eg. No. of hospital beds required for specific disease, health manpower planning)
For preventive services(eg. Screening programmes, immunization)

16. Trend in Proportion of one year old children immunized against measles -India
CES 2009 report

17. Natural History of Disease
Disease pattern in the community in relation to agent,host, and environment.
Eg. Natural history of atherosclerosis one third to two third of deaths due to IHD are sudden ie. Occur in less than 1 hr. Hospital studies could never have come to this conclusion,for most victims do not reach the hospital.
Eg. The natural course of HIV and TB or any human disease has been possible due to systematic observations

19. To Study Historically Rise and Fall of Disease in the Population
1) Health and disease pattern in community is never constant.
Eg. Smallpox rose, killed millions and eradicated
Epidemiology provides a means to study disease profiles and time trends in human population
By study of these trends we can make useful projections into the future and identify emerging health problems and their correlates.

20. TREND STUDY STUDYING THE PAST HISTORY FOR RISE AND FALL
STUDYING ITS CHANGING BEHAVIOUR
MAKING FUTURE PREDICTIONS
GIVING EARLY WARNINGS OR FEED -BACK

21. Syndrome identification
Identified by observing frequently
Till 1920 peptic ulcer was thought to be ingle entity. Based on its large scale epidemic, data and its analysis two entities duodenal and peptic ulcer clearly distinguish.
Recently obesity,dyslipidemia,HTN are risk factor for CHD

22. Identification Of Syndrome By Epidemiological Methods: some examples
Problem
Medical Data Available
Epidemiological Analysis
Result
Homogenicity of peptic ulcer
National Death Certificates
By site and social class, sex
Duodenal ulcer distinguish from Gastric
Histology of Bronchial Carcinoma
Large (national series of cases
By smoking, by sex
Squamous and undifferentiated ca are related to smoking
Unexplained still births
Clinical records of total population still birth certificate
By age and parity of mother , By period of gestation
A group of unexplained still birth distinguish by their post maturity and occurs especially in elderly primi

23. Searching for causes and risk factor
Eg. How do we say that smoking is risk factor for CHD, obesity for diabetes?
It is by observing thousands of obese and non obese and following them forward to see what % in each group develops diabetes(cohort epidemiological approach)
Asking hundreds of IHD people compared to hundreds of healthy people about smoking history(case control epidemiological approach)
Framingham cohort study

24. Search for causes Several causes  single disease
Multifactorial causation
eg. Smoking
air pollution Lung cancer
exposure to asbestosis
Single cause  several disease
Eg.Heamolytic Streptococcal tonsilitis
Streptococci Scarlet fever
Erysipelas

25. TO MEASURE RISK
By using various Epidemiological studies we can calculate Incidence rate, Relative risk, Attributable risk, Odds ratio
Eg. bearing a child with downs syndrome
Risk assesment for smokers and non smokers for cause of death. Cancer and CHD

26. Individual risk of bearing a ‘mongol child’ according to age of mother Source: Morris J N, uses of epidemiology, third edition

27. Stillbirths and deaths in the first four weeks of the life
Stillbirths and deaths in the first four weeks of the life. Infants of consanguineous and other marriages.

28. Epidemiological Studies
Patients
Clinical Trial
Randomized Controlled Studies
Healthy person
Field Trial
Communities
Community intervention studies
Community Trial
Experimental/ intervention Studies
Individuals
Follow-up/ Longitudinal
Cohort
Case-Reference
Case-Control
Populations
Correlational
Ecological
Cross-sectional Prevalence Individuals
Analytical studies
Descriptive studies
Observational studies
Unit of study
Alternate name
Type of study

29. Incidence rate=no. of new cases of disease during a. given time period
Incidence rate=no. of new cases of disease during a given time period x population at risk during that period
Relative risk incidence of disease among exposed incidence of disease among non exposed
Attributable risk
incidence of disease among exposed- incidence of disease among non exposed
x 100
incidence of disease among exposed

30. Lung Cancer Smoking + - 70(a) 6930(b) 7000(a+b) 3(c) 2997(d) 3000(c+d)
Incidence rate in exposed I(ex)=a/a+b=10/1000
Incidence in non exposed I(non ex)=c/c+d=1/1000
Relative risk= I(ex)/I(non ex)= 10
Attributable risk=I(ex)-I(non ex)/I(ex)x100=10-1/10x100=90%
Odds Ratio=ad/bc=10.09

31. References Morris J.N. uses of epidemiology third edition newyork 1975
AFMC text book
Park K. twenty second edition
Unicef and GOI CES 2009

32. THANKYOU