As a state epidemiologist, you are called upon to determine whether a recent oil

Question

  As a state epidemiologist, you are called upon to determine whether a recent oil spill in a water reservoir has caused an unusual type of acute arthritis. Within the county that you work, water is supplied by two independent reservoirs separated by 100 miles. The spill occurred in one of these reservoirs. The records from the Water Department clearly indicate which households receive water from which reservoir. Finally, you develop a case definition and institute a surveillance program to detect cases. To determine an association between the oil spill and arthritis, would you perform a cohort study or case-control study? Defend your choice (in a few sentences).

Explanation / Answer

Answer:

Case-control study.

Explanation:

The distinguishing basic difference between a case-control and a cohort study is whether the disease has already occurred or not.

In case-control studies, the disease has already occurred and the study begins with the disease and progress to the cause. This type of a study is also called retrospective study. It is done to identify risk factors and reasons as to why a specific disease has happened by studying from its course backward.

In cohort study, the effects have not occurred yet and the exposed subjects are followed to the future to know whether the disease might occur or not.

Here, An unusual type of Acute arthritis is the disease under study and this has already occurred in the county.The oil spill is the exposure. Initially, the entire population is divided into two groups, the case group and the control group.In one group called the case group or cases, arthritis is seen in exposed cases and in another group of cases, arthritis has occurred but they are unexposed to water contaminated with the oil spills. And a second major group called the control group where there is no arthritis but there are two groups one who are exposed to contaminated water and other who are unexposed.

This is done based on the already known information of which reservoir has been contaminated and which has not. This indirectly helps to rule out a major portion of the population as we have records of the households which receive water from that particular source.

Then the history of water usage of the affected populations(cases) are studied and matched with suitable unaffected controls and if the frequency of people with arthritis is observed to be more in the case group than in the control group, then there is said to be a positive association between the oil spill and arthritis.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.