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Epidemiology: Differences between Case – control and cohort study

Case – control study
  1. Proceeds from the outcome to cause
  2. Starts with cases of disease
  3. Tests if the suspected risk factor occurs more often in the cases than that in the controls
  4. Usually the first study for testing a hypothesis
  5. Requires fewer number of participants
  6. Yields the results relatively earlier
  7. Suitable for rare diseases
  8. Cannot directly estimate the relative risk hence calculates the ‘Odd’s ratio’ (OR)
  9. Only one outcome (disease) can be studied
  10. Inexpensive

Epidemiology: Monitoring and Evaluation

Definition of ‘Monitoring’:
Monitoring is the performance and analysis of routine measurements aimed at detecting changes in the environment or health status of the population.
Monitoring can be of variety of activities like:
• Health program
• Air quality
• Water quality
• Intrauterine growth
• Nutritional status
• Functioning of a health facility etc.

Definition of ‘Surveillance’:

Epidemiology: Advantages and disadvantages of cohort study


  • Incidence can be directly calculated
  • Direct estimation of the relative risk (RR)
  • More than one outcome of the risk factor can be studied
  • Dose response relationship with exposure can be studied
  • Temporal association of the exposure with the outcome can be seen
  • Certain biases like recall bias, interviewer’s bias are not a problem


Epidemiology: Types of Epidemiological Studies

There are two broad types of epidemiological studies:
1. Observational studies – we do not interfere in the process of the disease, but simply observe the disease and the associated factors.
2. Experimental studies – deliberate intervention is made and the effect of such intervention is observed.

Observational studies include:
Descriptive study and
Analytical study – Case control and cohort studies are the two types of analytical observational studies

Input-Output Analysis

It is a tool for analysing the interaction between the different sectors of an economy. An understanding of inter-sectoral interactions can aid in optimizing the planning of public health policies.
Such analyses result in creation of ‘Input-output matrices’.
The main function is to make it possible to evaluate a sector’s requirements to satisfy a given demand for goods and services.

Difference b/w Cost-Benefit and Cost-Effective Analysis

• WHO, 1974. Modern Management Methods and the Organization of Health Services; Geneva
• WHO, 2006 . Guidelines for conducting cost–benefit analysis of household energy and health interventions; eds: Guy Hutton,Eva Rehfuess. WHO press, Geneva.
• WHO, 2003. Who Guide to Cost- Effectiveness Analysis; Geneva
• Park’s Textbook of Preventive and Community Medicine. 24th ed, 2017, Bhanot Publishers, Jabalpur

Cost Effective Analysis (CEA)

• Usually, once a particular welfare policy is selected after CBA, Cost effective analysis is used to identify the least expensive method of attaining that definite result.
– CEA involves choosing one among different possible ways for achieving the desired result.
– E.g. it was calculated that ‘reduction in indoor air pollution’ would result in greatest economic benefit (after CBA) to the population, various possible ways of achieving this are analyzed using cost – effective analysis

Cost Benefit Analysis (CBA)

• Public funds are never sufficient. Hence, there is a need to rank various projects so that the officials can select the intervention that would deliver the highest monetary return to the population
• The next ranked intervention would be considered when more funds become available or after the first one is complete
• Hence, in CBA, costs and benefits are expressed in monetary terms i.e.'cost= money spent' and 'benefit = money saved +money earned'.


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