True about cohort studies is:
|A||Proceeds from cause to effect|
|B||Cohorts are identified prior to the appearance of disease under investigation|
|C||Study groups are observed over a period of time to determine the frequency of disease among them|
|D||All of the above|
COHORT STUDY is a type of analytical study which is usually done to obtain additional evidence to refute or support the existence of an association between suspected cause and disease. Cohort is defined as a group of people who share common characteristic or experience within a defined time period. The features of cohort studies are as under:
1. Cohorts are identified prior to the appearance of disease under investigation.
2. Study groups are observed over a period of time to determine the frequency of disease among them.
3. Proceeds from cause to effect.
Case control study:
- An epidemiological study where a group of individuals with disease (CASE) are compared with a group of individuals who are not suffering from disease (CONTROLS) in terms of specific disease causing exposures.
- Since the starting point is a group of people who already have suffered from the disease, this is labeled as a retrospective study.(BACKWARD LOOKING STUDY)
- Advantages of case control studies
- Relatively quick and easy to undertake.
- Relatively cheap to undertake.
- Only method useful in rare diseases.
- Not enmeshed in problems of follow-up as the data is collected at one point in time.
- Can be used to study the effect of many exposure variables on a single disease outcome.
A case control study on the other hand only provides an estimate of risk in the form of an odd’s ratio.