Case control vs retrospective cohort4/4/2023 It is always important to find out the following: Did the researchers select a study type that will actually allow them to find the answers they are looking for? You can’t use a survey to find out what is causing a particular disease, for instance. How reliable are the different types of studies?Įach type of study has its advantages and disadvantages. Still, case-control studies can help to investigate the causes of a specific disease, and answer questions like these: But the people they interview might no longer remember whether they were, for instance, exposed to certain risk factors in the past. Because the researchers usually ask about past events, they are dependent on the participants’ memories. But it is often difficult to tell which people are the most similar to each other and should therefore be compared with each other. They are also not as expensive or time-consuming as RCTs or cohort studies. So case-control studies are generally retrospective.Ĭase-control studies are one way to gain knowledge about rare diseases. Then the two groups are interviewed, or their medical files are analyzed, to find anything that might be risk factors for the disease. They can answer questions such as:Ĭase-control studies compare people who have a certain medical condition with people who do not have the medical condition, but who are otherwise as similar as possible, for example in terms of their sex and age. In a retrospective study, the result (the illness) has already occurred before the study starts, and the researchers look at the patient's history to find risk factors.Ĭohort studies are especially useful if you want to find out how common a medical condition is and which factors increase the risk of developing it. But the outcomes that they want to measure and other possible influential factors can be precisely defined beforehand. In a prospective study, the result that the researchers are interested in (such as a specific illness) has not yet occurred by the time the study starts. Cohort studies can have a prospective (forward-looking) design or a retrospective (backward-looking) design. Cohort studies often include people who are healthy at the start of the study. The researchers then observe how the health of the people in both groups develops over the course of several years, whether they become ill, and how many of them pass away. Or one group may be exposed to a hazardous substance at work, while the comparison group isn't. In a cohort study, two (or more) groups that are exposed to different things are compared with each other: For example, one group might smoke while the other doesn't. RCTs can answer questions such as these:Ī cohort is a group of people who are observed frequently over a period of many years – for instance, to determine how often a certain disease occurs. Randomized controlled trials provide the best results when trying to find out if there is a cause-and-effect relationship. Random allocation ensures that differences between the results of the two groups at the end of the study are actually due to the treatment and not something else. If doctors decided themselves which patients should receive which treatment, they might – for instance – give the more promising drug to patients who have better chances of recovery. The assignment to groups has to be random in order to make sure that only the effects of the medications are compared, and no other factors influence the results. Ideally, the assignment to the various groups is done "double blinded," meaning that neither the participants nor their doctors know who is in which group. Things like the appearance and taste of the drug and the placebo should be as similar as possible. Then one group receives the new drug A, for example, while the other group receives the conventional drug B or a placebo (dummy drug). In RCTs participants are randomly assigned to one of two or more groups. “Randomized” means divided into groups by chance. And a study on treatment for a stuffy nose may be much shorter than a study on a drug taken to prevent strokes. How the effect of the treatment should be measuredįor instance, a medication used to treat menopause symptoms needs to be tested on a different group of people than a flu medicine.
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