4. DEFINITION OF EPIDEMIOLOGY
Thestudy of the distribution and determinants of disease or
health related states and events in specified populations, and
the application of the knowledge for disease prevention and
control.
5. COMPARISON BETWEEN CLINICAL PRACTITONERAND
EPIDEMIOLOGIST
S. No. CLINICAL PRACTITONER EPIDEMIOLOGIST
1. What is wrong with this patient What are disease in the population?
How common are they?
Whois most affected?
2. History and Examination Population based surveys
3. Whyis this person ill? What are the risk factors for the condition ofthe
population?
4. Investigations Epidemiological studies
5. How shall I treat the patient What control strategies are needed to reduce
this disease in population?
6. Medication /Surgeries/ Nothing Intervention Studies
7. Patients comes to you Youhave to got to Population or Source of data
about the population
6. USES OFEPIDEMIOLOGY
Establishing the magnitude and distribution of healthneed
Identifying high risk groups
Health Situation Analysis/Health StatusAssessment
Planning provision of health care services
Evaluate the impact of current services
7. USES OFEPIDEMIOLOGY
Identify factors , if they could be removed, would prevent the
disease or modify its course
Knowing which is the most effective wayof delivering a
curative or preventive measure
Determine cost and expected effectiveness of a proposed
strategy
9. DISEASE FREQUENCY
Thebasic measure of disease frequency is rate or ratio.
These are essential for comparing disease frequency in
different populations or subgroups of the same populationin
relation to suspected casual factors.
Such comparisons may yield clues to disease etiology- which
in turn is a vital step in the development of strategies for
prevention or control of health problem
10. DISTRIBUTION OF DISEASE
It occurs in patterns in acommunity.
Thedistribution patterns in various subgroups of the
population should be studied by time, place and person.
This study helps in formulation of etiological hypothesis .
11. DETERMINANTS OFDISEASE
Identifying the underlying causes (or risk factors ) of disease.
It helps in developing scientifically sound health programs,
interventions and policies
It also helps in understanding the chronic disease causation.
12. AIM OFEPIDEMIOLOGY
Theultimate aim of epidemiology is to lead to effectiveaction
1. T
oeliminate or reduce the health problem or its
consequences
2. T
opromote the health and well-being of society as awhole.
13. EPIDEMIOLOGICAL APPROACH
Asking Questions and making comparisons
Related to health Events
What is the problem?/ andMagnitude?
Where did it happen?
When did it happen?
Who are affected?
Whydid it happen?
14. EPIDEMIOLOGICAL APPROACH
Questions Related to Health Action What
can be done to reduce the problem? How
can it be prevented?
What action should be taken by the community? Bythe Health
Services? Byother sectors?
What resources are required?
How are the activities to be organized?
What difficulties may arise in implementation?
15. EPIDEMIOLOGICAL APPROACH
Making Comparison -Thebasic approach in epidemiology is
to make comparisons and draw inferences.
This may be comparison of two (or more groups) -one group
having the disease (or exposed to risk factor) and the other
group(s) not having the disease (or not exposed to risk factor)
Bymaking comparisons, the epidemiologist tries to find outthe
crucial differences in the host and environmental factors
between those affected and not affected.
16. TOOLS OF MEASUREMENT
Basic tool of measurement are:
Rates: It measures the occurrence of some particular event in a
population during a given period of time.
1. Numerator is part of the denominator i.e comparison between
2 same entities
2. Time is mentioned
3. Multiper is present .e.g 100,1000 …..etc
Infant Mortality rate = Total number of Infants death x1000
Total live birth
17. TOOLS OF MEASUREMENT
Ratio: Arelation in size between two random quantities.
1. Numerator is not part of denominator
2. Comparison between 2 different entities
3. Time is may not be mentioned
4. Multiplier for e.g 1000,10000….etc
Ex-Maternal Mortality ratio= Total number of Maternal death x1,00,000
Live birth
18. TOOLS OF MEASUREMENT
Proportions: It is a ratio indicting the relation in magnitudeof
a part of the whole.
1. Numerator is part of Denominator
2. Times is not mentioned
3. Multiplier always 100 . Calculated in Percentage
19. MEASUREMENTS IN EPIDEMIOLOGY
Is very broad and unlimited and includes the following :
Measurement of Mortality
Measurement of Morbidity
Measurement of Disability
Measurement of presence ,absence of disease or distribution
of disease.
Measurement of medical needs ,health care needs ,health
care facilities.
20. MORTALITY INDICATORS
CRUDEDEATHRATE(CDR)– It is the simplest indicator of mortality
It is defined as the number of deaths from all causes per 1000 estimated
mid year population in one year (MYP),in given place
CDR=No of deaths in an area in a year X1000
Total MYP
SPECIFICDEATH RA
TE- Specific death rate may
1.Agespecific death rate
2.Sex specific death rate
3.Disease specific death rate
SDR=No of deaths from a specific cause in a year X100
Total MYP
21. MORTALITY INDICATORS
PROPORTIONALMORTALITYRATE-It is expressed as the number of
deaths due to particular cause per 100/1000 totaldeaths
1.Proportional mortality from a specific disease
2.Under 5 proportionate mortality rate
3.Proportional mortality rate for aged 50 years andabove
It is the simplest measure of estimating the burden ofdisease
It indicates magnitude of preventablemortality
22. MORTALITY INDICATORS
CASEFATALITYRATE-Represents killing power of a disease. It is closely
related to virulence of organism.
CFR=Total number of death due to disease X100
Total no of cases due to disease
SURVIVALRATE-Is the proportion of survivors in a group , studied and
followed over period of time
It is used to describe prognosis on certain diseasecondition
Useful in cancer studies
Survival period is measured from date of diagnosis or start oftreatment
23. MORBIDITY INDICATORS
Incidence: Number of new cases, episodes or events occurring over a defined
period of time.
INCIDENCE= No. of new cases of disease in a year x 1000
Total population at risk
Incidence is RA
TE,expressed per 1000
Special types of Incidence rate
1.Attack rate- Incidence rate used when population is exposed for a small interval of
time . For example –epidemic
2.Secondary attack rate- It is number of exposed person developing diseasewithin
range of incubation period following exposure to the primary case
24. INCIDENCE
Incidence may change (increase or decrease) with the following
factors:
1. Introduction of a new risk factor (e.g., contraceptive and increase in
Thromboembolism, food additives and cancer)
2. Changing habits.
3. Changing virulence of causative organisms.
4. Changing potency of treatment or intervention programs.
5. Selective migration of susceptible persons to an endemic area,
which increase the incidence of the disease.
25. PREVALENCE
Prevalence – It is total current (Old+New )cases in a given population over apoint
or period of time
Prevalence = No of total (old+new)cases of a disease in a year X100
Total population
Prevalence is PROPORTION.Expressed Inpercentage
26. PREVALENCE
These rates are typically obtained from cross –sectional studies;
occasionally, they are based on registers of specific disease.
Prevalence depends on two main factors:
1. Previous incidence ,and
2. Duration or chronicity of disease.
When both incidence and during of a specific disease are relatively
stable,
Prevalence (P) = incidence (I) X duration (D)
27. PREVALENCE
Prevalence may change over time in response to
Changes in incidence,
Changes in disease duration and chronicity (e.g., some disease may
because of high recovery
become shorter in duration or more acute
rate or high case fatality rate),
Intervention (preventive) programs,
Selective attrition (e.g. selective migration of cases or of susceptible
or immune persons )
Changing classification of what constitutes an “active ” case and
whether an “ arrested” case is counted ornot.
28. DISABILITY MEASURE
DAL
Y(DISABILITYADJUSTEDLIFEYEARS)– It is a measure of overall disease
burden, expressed as the number of years lost due to ill-health, disability orearly
death.
Best indicator for Burden of disease it can express both mortality and alsodisability
caused by the disease
DALY=Years of life lost due to premature death+ Yearslived with the disability
OneDaly is equal to one year of healthy lifelost
QALYS(QUALITYADJUSTED LIFE YEARS)-It is measure of disease burden, including
both the quality and the quantity of life lived. It is used in evaluation to assess the
value of medical interventions.
OneQAL
Yis equal to one year in perfecthealth.
29. DISABILITY RATES
SULLIVAN’sINDEX-Also known as Disability Free Life Expectancy
(DFLE)is a method to compute life expectancy free of disability. It is
calculated by formula:
SI = Life expectancy -Duration of disability
HALE(HEALTHADJUSTEDLIFEEXPECTANCY)-Itadjusts overall life
expectancy by the amount of time lived in less than perfect health
30. MEASUREMENT OF MEDICAL NEEDS, HEALTH CARE NEEDS,HEALTH
CARE FACILITIES
Health care delivery indicators includes
1. Doctor –population ratio
2. Doctor-nurse ratio
3. Population –bed ratio
4. Population per health centre
5. Population per traditional birth attendant
31. INDEX
Index is combination of indicators .
HDI( HUMANDEVELOPMENTINDEX)-It is measure of average
achievement in key dimensions of human development: a long and
healthy life, being knowledgeable and have a decent standard of
living.
It includes
1. Knowledge- Mean years of schooling and Expected years of schooling
2. Income – Per Capita Income
3. Life expectancy at birth.
32. INDEX
Physical Quality of life Index (PQLI)-Is an attempt to measure
the quality of life or well-being of acountry.
It includes
1. Infant mortality rate
2. Literacy rate
3. Life expectancy at Age1
33. SUMMARY
Epidemiology is the study of the distribution and determinants of disease or health
related states and events in specified populations, and the application of the knowledge
for disease prevention and control.
Tools for measurement is Rate Ratio Proportion . INCIDENCEis rate . Prevalence is
proportion
Mortality indicators are 1.Crude death rare 2. Specific death rate 3. Proportional mortality
rate – Simplest measure to estimate the burden of disease 4. Case Fatality Rate
(virulence) 5.Survival rate – tell the prognosis ofdisease
Morbidity Indicators – Incidence –no of new cases/ total population*1000.
Prevalence – Total number of new plus old case /total population*100
Disability indicators- DAL
YQAL
YHALE
Index- Human development index / Physical quality lifeindex
