epidemiology

1. EPIDEMIOLOGY

Gk, “epidemios” meaning prevalence
▫ terms epi = upon, among
▫ demos = people, district
▫ logos = study, word, discourse
• Study of distribution and determinants of disease
▫ factors affecting the health and illness of populations
and serves as the foundation and logic of
interventions
made in the interest of public health and preventive

2. The study of the distribution and determinants of
health related states or events in a specified population
and application of this study to the control of health
problem
(WHAT.WHY.WHEN..HOW.WHER Why
:
STUDY WHAT COMES UPON PEOPLE
Diferent typs of biological,physical,social
stresses

3. Uses of
Epidemiology
1-Describing the normal biologic process
2. Understanding actual history of diseases
3. Revealing distribution of disease
4. Identifying determinants of disease
5. Testing hypotheses for disease prevention
and control
6. Planning and evaluating health care services

4. Epidemiological approach
 Asking question
 WHAT IS :
 EVENT ,MAGNITUDE,
 WHERE IS HAPPEN
 WHENE IS HAPPEN
 WHO ARE AFFECTED
 WHY DID IT HAPPEN

5. TOOLS OF MEASUREMENT
 1 Disease frequency :
 rate , ratio and proportions
 Rate :
 Death rate =number of deaths in one year × 1000
 mid year population
 RATIO s the result of dividing one quantity by another x /y
 The ratio of white BC TO RED BLOOD CELLS IS 1/ 600
PROPORTION
THE NUBBER OF CHILDREN WITH SCABIES AT CERTAIN TIME
THE NUMBER OF CHILDREN WITH MALNUTRION AT THE SAME TIME

6. INCIDENCE

Expressed as a rate (cases per
population per time)
• Ex:
▫ Annual death rate: 60 people in a
city of 300,000 died of oral
cancer on 1992
▫ IR = cases/person-time (2 deaths
per 10,000 in year 1992)

7. AIM OF EPIMIOLOGY
 To describe the distribution and magnitude of the
problem
 to identify etiological and (risk factor )
 Provide a data essential to planning and prevention
the ultimate aim is
eliminate and reduce the health problem
to promote the health and well being

8. MEASUREMENT OF MORTALITY
Crude death rate
 number of deaths X 1000
 mid year population
The crude death summaries :
 population composition
 Age specific rates (which reflect
 probability of dying )

9. :
MORTALITY (to be continued)
Specific death rates :
TOTAL No of deaths from certain disease during CY X1000
Mid year population
CASE FATALITY rate :
Total number of D due particular disease X 100
Total number of cases due to the same disease

10. MORBIDITY
 Morbidity ;
 Define as any departure from physiolgical
wellbeing
 The value morbity data may be summaries e as follow ;
 Describe the extent and nature of the disease
 They usually provide more comprehensive and more
 accurate information of the disease.
 The etiological as starting point .

11. INCIDENCE
 Incidence ;
 is define as the number of new cases
occurring in a defined population during specified tim
 The formula ;
No of new cases of specific disease during a given P .T X 1ooo
Population at risk during the same period of time
 Example
 Cases 500, 30,000=500/30000 X100= 16,7per1000per Y

12. Specific incidence rate
 Attack rate :
used only when the population are exposed
 To risk for limited period of time as during epidemic
 To reflect the extent of epidemic
 The formula is ;
No of new cases of specified disease during a specified × 1000
Total population at risk during the same interval
Uses of incidence rate ;
a) Control of disease
b) Research to etiology and pathogenesis

13. PREVALANCE;
refers specifically to all current cases (old and new)
existing at given period of time in given period of population
the formula is ;
No of existing cases (old and new )of specific disease
during a given period of time interval × 100
estimated md interval population at risk

14. HYPOTHESIS ;
It is a supposition arrived from an
observational or reflection . The hypothesis coul be tested
using the techniques pf analytical epidemiological after
which it may be accepted or rejected
POPULATION AT RISK ;
The part of population which is susceptible
to get a disease