What is an Observational Study?
In an observational study, the researcher observes the population. Observational differ from experimental studies in that it does not involve interference or manipulation of the research subjects and no treatment groups are involved. Observational study involves the systematic observation of behavior: scientists watch and record what the population say and do.
Types of Observational Studies
Observational studies are grouped based on different reasons. Choosing the best type is important in achieving an effective result. Most scientists use observational studies in research where randomized experiments are found unethical. They are also effective when looking at the cause of a condition or illness and the treatment of rare conditions.
In a case-control study, the researcher enrolls participants with the disease of interest (case group) and others without the disease (control group). The research team then compares past exposures between the two groups. The control group is used to estimate the expected amount of exposure in that population. If the rate of exposure among the case group is higher than the rate in the control group, the disease is said to be related to that exposure. A case-control study aims to provide a reasonable estimate of the expected exposure or baseline of the disease of interest.
In a cohort study, the scientist determines whether each participant is exposed or not and then tracks the population to determine if they develop the illness they are researching about. Keep in mind that a cohort study differs from a clinical trial in that in a cohort study, the researcher observes and does not manipulate or interfere with the participant. This observational study involves a big group of people with similar characteristics. The scientist compares the rate of the disease of interest in the exposed group with the rate in the unexposed group. The unexposed group is used for comparison, giving an estimate of the expected rate of the illness occurrence within a certain population.
A cohort study can either be prospective (follow-up) or retrospective. In a prospective cohort study, scientists carry out the study from the present time into the future. Participants are enrolled and then followed over time to determine the occurrence of the disease of interest. On the other hand, a retrospective cohort study is carried out at the present time and looks to the past to identify disease occurrence. In this study design, both the outcome and exposure have already occurred. Similar to a prospective cohort study, the researcher compares the rate of the disease in the exposed and unexposed groups. In a retrospective cohort study, researchers rely on existing data records of the participants to conduct the study.
In observational study there is no control group involved and it does not explore cause and effect but instead looks at prevalence. Scientists study data from a sample of people from a population and measure their exposures and health outcomes simultaneously. They observe and record information about something existing in the population at the same time without any manipulation or interventions.