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

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

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

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

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

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

John memorial and public house on broadwick street, Soho

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)

“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)

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.

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

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

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.

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

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)

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

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

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.

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

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

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

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

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

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

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

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.

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

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 1000 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

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

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

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