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Cohort Study Design
Cohort study design looks at the association between and disease in a prospective manner. The study starts with a group of people who are exposed to or are likely to be exposed to the risk factors(s) during the course of study and eventually may or may not develop the disease. Such group of persons sharing certain common characteristics and carrying risk of being exposed to the probable factor(s) constitute a cohort.
Essentially cohort studies are prospective because they examine the effect of risk factors on the disease in a prospective manner, but the point of observation or data collection may not be prospective. Multiple factors can be studied during the same time period on the same population group; multiple outcomes may also be studied simultaneously. It may be possible to select a group of people who may have already developed the disease of interest at the start of the study but may be traced back historically to belong to a cohort, and the exposure to the risk factors may be retrospective or mixed, however the method remains longitudinal on time scale, hence the more appropriate term is ‘longitudinal study.’
3. Cohort Studies Are Done In The Community
Like case control study, in cohort study also, information is collected about the exposure to the risk factors and the occurrence of disease. Since people report to the hospital about the disease when they have already acquired the disease so these studies cannot be conducted in the hospital set up and is essentially community based. A community for cohort studies may be a residential area, or any community like school, college, workplace,etc. Sometimes cohort s are selected on the basis of single event in people life like date o birth, exposure to radiation during an accident, or exposure to drugs whose side effects may manifest as disease.
Cohort studies are often done (1) to evaluate the effectiveness of the health services or (2) to further confirm the etiological basis of the disease. The studies are always longitudinal and may take years to complete , so they are fairly expensive If the chance of occurrence of a disease or health problem on exposure to the offending agent is minimal or if the expected benefit from the proposed health measure is marginal, cohort studies should be executed on fairly large sample and with great precision to arrive at meaningful and statistically significant results.
To be continued…………
- Definition
Cohort study design looks at the association between and disease in a prospective manner. The study starts with a group of people who are exposed to or are likely to be exposed to the risk factors(s) during the course of study and eventually may or may not develop the disease. Such group of persons sharing certain common characteristics and carrying risk of being exposed to the probable factor(s) constitute a cohort.
- Cohort Studies are longitudinal.
Essentially cohort studies are prospective because they examine the effect of risk factors on the disease in a prospective manner, but the point of observation or data collection may not be prospective. Multiple factors can be studied during the same time period on the same population group; multiple outcomes may also be studied simultaneously. It may be possible to select a group of people who may have already developed the disease of interest at the start of the study but may be traced back historically to belong to a cohort, and the exposure to the risk factors may be retrospective or mixed, however the method remains longitudinal on time scale, hence the more appropriate term is ‘longitudinal study.’
3. Cohort Studies Are Done In The Community
Like case control study, in cohort study also, information is collected about the exposure to the risk factors and the occurrence of disease. Since people report to the hospital about the disease when they have already acquired the disease so these studies cannot be conducted in the hospital set up and is essentially community based. A community for cohort studies may be a residential area, or any community like school, college, workplace,etc. Sometimes cohort s are selected on the basis of single event in people life like date o birth, exposure to radiation during an accident, or exposure to drugs whose side effects may manifest as disease.
- Utility
Cohort studies are often done (1) to evaluate the effectiveness of the health services or (2) to further confirm the etiological basis of the disease. The studies are always longitudinal and may take years to complete , so they are fairly expensive If the chance of occurrence of a disease or health problem on exposure to the offending agent is minimal or if the expected benefit from the proposed health measure is marginal, cohort studies should be executed on fairly large sample and with great precision to arrive at meaningful and statistically significant results.
To be continued…………
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