Most attorneys who practice personal injury litigation are exposed to scientific articles. These articles can be confusing to the uninitiated. In this week’s Sadaka’s Science Tip I am going to explain the types of studies that are reported in these articles.
Let’s start at the beginning. A scientific article usually reports the results of a study (there are other types of articles, but we will not address them here). There are two main categories of studies: experimental and observational.
Experimental studies focus on the prevention or treatment of disease. For example, a group of cancer patients are studied to determine if radiation works to treat their disease. The second category of study is observational.
Observational studies focus on the cause, prevention and treatment of disease. For example, a study is conducted to look for the number of cancer diagnoses in a specific area one year after a nuclear accident in that area. Our focus is on observation studies.
I am going to describe three of the four types of observational studies: 1. cohort; 2. case control; and 3. cross-sectional. The fourth type is called an ecological study and will not be addressed here. But before we continue, we must stop a moment to discuss some key concepts.
The first is the concept of exposure. Exposure is simply the chemical, medication, type of surgical procedure or any other event that you want to study. For example, if you want to study how violence on T.V. affects children then the exposure will be violent T.V. programming. Another example would be to measure the number of adverse events following a surgical procedure. Here the surgical procedure would be the exposure. The second important concept is the outcome or disease occurrence.
When a study is started there should be some outcome you are trying to measure. Using our previous example about violence and T.V., the outcome of the study could be measured in the number of violent acts that occur when children are exposed to violence on T.V.. The number of violent acts would be known in epidemiological terms as “disease occurrence”.
Cohort
The basic concept behind a cohort study is pretty easy to understand. In a cohort study, the participants in the study are put into group according to their level of exposure. Using our violent T.V. example, children would be put in groups according to the amount of violent T.V. they watched (exposed to). Once the subjects are put into groups they are studied to determine the disease occurrence (violent acts in our example).
Case Control
In this type of study we have two groups of individuals, cases and controls. Cases are typically those who are exposed to the chemical, medication or whatever event is being studied. Controls are usually those who lack the exposure. At the end of the study researchers compare the two groups to determine whether or not there is an association between the exposure and disease occurrence.
Cross Sectional
Cross-sectional studies can be best understood relationship in context. A cross-sectional study would be the incidence of cancer in all of the individuals who lived within a 50-mile radius of Chernobyl when it exploded. In other words, a cross-sectional study measures an exposure and a disease in a well-defined population at a single point in time.
Scientific studies can be complex and understanding the strengths and weaknesses of each type of study is an art form onto itself.