1. Descriptive Epidemiology
Manish Chaudhary
BPH(IOM), MPH( BPKIHS)

2. Descriptive epidemiology
Descriptive epidemiology is the first phase of epidemiological investigation.
The study concerns with the description of the health status of a community in terms of time, place and person.

3. Steps in descriptive epidemiology
Defining the population
Defining the disease under study
Describing the disease in terms of time, place and person
Measurement of disease
Comparing with known indices
Formulation of an aetiological hypothesis

4. Defining the population
The defined population can be the whole population in a geographic area or a representative sample taken from it.
The defined population can be selected group such as age and sex group, occupational groups, hospital patients, school children etc.
The study population needs to be large.

5. Defining the disease under study
The disease under studies should be defined in both clinical and epidemiological terms.
The 'operational definition' of disease i.e. a definition by which the disease or condition can be identified and measured is important.
The case definition according to disease must be adopted throughout the study.

6. Describing the disease
The disease occurrence and distribution of disease are described in terms of
time
place
person
Includes systematic collection and analysis of data.

7. Time distribution
The disease rate may vary by the time of its occurrence i.e. by week, month, year etc.
There are three kinds of time trends of disease occurrence:
Short terms fluctuations
Periodic fluctuations
Long term or secular trends

8. Short term fluctuations
Common source epidemics-well of contaminated water; food poisoning
Propagated epidemics- person to person, arthropod vector, animal reservoir
Slow modern epidemics- road accidents, blood cancer, hypertension
Periodic fluctuations
Seasonal trend
Cyclic trend
Long term or secular trends
Polio, malaria

9. Place distribution
The geographic distribution of the disease varies because of variation in cultures, standard of living and external environments. The mortality, morbidity varies due to socioeconomic factors, dietary differences, cultures and behavior.
International variations
National variations
Rural urban variations
Local distributions

10. Person distribution
The disease should be described by age, sex, ethnicity, marital status, occupation, social class, behavior, stress, migration etc.
Age is probably the single most important personal attribute because almost every health related events or states vary with age.
In general, males have higher rate of illness and death than females for a wide range of diseases.

11. Measurement of disease
After defining the disease, the disease load should be measured in population.
The disease should be measured in terms of mortality, morbidity - prevalence, incidence.
Comparing with known indices
The disease should be compared with known indices such as with data from previous similar studies, national data or national and international standards.
Formulation of hypothesis
The descriptive epidemiology helps to formulate hypothesis relating to disease aetiology.
The epidemiological hypothesis should specify the population, the causes, the excepted outcome, dose response relationship, time response relationship.

12. Thank You