What type of observational study was this? explain.

Most people think of a traditional experimental design when they consider research and published research papers. There is, however, a type of research that is more observational in nature, and it is appropriately referred to as “observational studies.”

There are many valuable reasons to utilize an observational study design. But, just as in research experimental design, different methods can be used when you’re considering this type of study. In this article, we’ll look at the advantages and disadvantages of an observational study design, as well as the 3 types of observational studies.

What is Observational Study Design?

An observational study is when researchers are looking at the effect of some type of intervention, risk, a diagnostic test or treatment, without trying to manipulate who is, or who isn’t, exposed to it.

This differs from an experimental study, where the scientists are manipulating who is exposed to the treatment, intervention, etc., by having a control group, or those who are not exposed, and an experimental group, or those who are exposed to the intervention, treatment, etc. In the best studies, the groups are randomized, or chosen by chance.

Any evidence derived from systematic reviews is considered the best in the hierarchy of evidence, which considers which studies are deemed the most reliable. Next would be any evidence that comes from randomized controlled trials. Cohort studies and case studies follow, in that order.

Cohort studies and case studies are considered observational in design, whereas the randomized controlled trial would be an experimental study.

Let’s take a closer look at the different types of observational study design.

The 3 types of Observational Studies

The different types of observational studies are used for different reasons. Selecting the best type for your research is critical to a successful outcome. One of the main reasons observational studies are used is when a randomized experiment would be considered unethical. For example, a life-saving medication used in a public health emergency. They are also used when looking at aetiology, or the cause of a condition or disease, as well as the treatment of rare conditions.

Case Control Observational Study

Researchers in case control studies identify individuals with an existing health issue or condition, or “cases,” along with a similar group without the condition, or “controls.” These two groups are then compared to identify predictors and outcomes. This type of study is helpful to generate a hypothesis that can then be researched.

Cohort Observational Study

This type of observational study is often used to help understand cause and effect. A cohort observational study looks at causes, incidence and prognosis, for example. A cohort is a group of people who are linked in a particular way, for example, a birth cohort would include people who were born within a specific period of time. Scientists might compare what happens to the members of the cohort who have been exposed to some variable to what occurs with members of the cohort who haven’t been exposed.

Cross Sectional Observational Study

Unlike a cohort observational study, a cross sectional observational study does not explore cause and effect, but instead looks at prevalence. Here you would look at data from a particular group at one very specific period of time. Researchers would simply observe and record information about something present in the population, without manipulating any variables or interventions. These types of studies are commonly used in psychology, education and social science.

Advantages and Disadvantages of Observational Study Design

Observational study designs have the distinct advantage of allowing researchers to explore answers to questions where a randomized controlled trial, or RCT, would be unethical. Additionally, if the study is focused on a rare condition, studying existing cases as compared to non-affected individuals might be the most effective way to identify possible causes of the condition. Likewise, if very little is known about a condition or circumstance, a cohort study would be a good study design choice.

A primary advantage to the observational study design is that they can generally be completed quickly and inexpensively. A RCT can take years before the data is compiled and available. RCTs are more complex and involved, requiring many more logistics and details to iron out, whereas an observational study can be more easily designed and completed.

The main disadvantage of observational study designs is that they’re more open to dispute than an RCT. Of particular concern would be confounding biases. This is when a cohort might share other characteristics that affect the outcome versus the outcome stated in the study. An example would be that people who practice good sleeping habits have less heart disease. But, maybe those who practice effective sleeping habits also, in general, eat better and exercise more.

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01-02-2021

From a methodological perspective, clinical research can have an experimental or an observational design, which translates into experimental or observational trials or studies, respectively. In an experimental design, the investigator establishes the treatment, selects the patients, indicates what variables will be measured, etc. In an observational study, investigators can only observe the events without interfering or modifying the conditions of routine clinical practice.

Observational studies can be classified as:

• Descriptive:
• Analytical:
  • Cohort studies
  • Case-control studies

Classification of Observational Studies:

Descriptive Studies: They answer questions such as “who,” “where” and “when,” describing events as an approach to reality. Descriptive studies include case reports and case series.

1. Case Reports: They are detailed studies of one or more occurrences, usually less than 10, which comprise about 30% of original published articles in journals. Case reports are used to describe rare findings and, in general, they serve to formulate a hypothesis that will later have to be tested in other studies. Since it is a reduced group of patients and due to the selection method, case report conclusions are usually biased.
2. Case Series: They are similar to case reports but they involve a larger number of patients (usually more than 10) with a certain adverse reaction or disease and exposure. In general, investigators try to establish a relationship between the disease and exposure using statistical evidence but without a control group for comparison.

Analytical Studies: They answer the question "how." These controlled studies try to know reality by exploring reasons and causes and checking hypotheses. The most common are cohort studies and case-control studies.

1. Cohort Studies: They are used to study incidence, causes and prognosis. Because they measure events in chronological order they can be used to distinguish between cause and effect. Cross-sectional studies are used to determine prevalence. They are relatively quick and easy but do not allow to distinguish between cause and effect. In this type of study, groups of exposed and non-exposed patients (control group) are selected and allocated to a certain treatment, which is the object of the study. When they are used to assess the safety of a treatment, a follow-up over time is conducted to analyze whether patients present or not with a certain adverse reaction, disease or, in general, an event that may have a negative impact on health. Cohort studies are usually prospective and, less frequently, retrospective. Follow-up is usually long to allow time for the disease or the adverse reaction under study to occur. Furthermore, if this reaction is rare, the sample size of the cohorts must be very high. This type of design is the most appropriate to study relatively common events that may occur after short exposure to treatment or when treatment is rare.
2. Case-Control Studies: Two groups of patients are selected: a case group, which includes patients with a certain adverse reaction (disease, harmful effect, etc.), and a control group, which includes randomly selected patients of the same population as the case group but who do not show that adverse reaction. Then, both groups are studied for a certain time (window of exposure) prior to the beginning of the adverse reaction or exposure to the risk factor under study (drug or treatment). Its design is retrospective because, at the time of study start, the events have already occurred. This design is the most appropriate when the adverse reaction under study is rare or highly unusual.

Observational studies are mainly useful to increase knowledge about drug safety but, on the other hand, they present several disadvantages, such as lack of efficiency, since they are very expensive and the patient sample is usually relatively reduced and highly homogeneous; therefore, in general their results have little external validity.

23-12-2021

A clinical trial finishes when the last patient enrolled completes all their visits and follow-ups. However, a clinical trial may be terminated early for different reasons.

30-11-2015

In the field of clinical research, perhaps one of the areas that has most clearly evolved over the years is data management, particularly with respect to the methods of data collection and database creation and preparation for subsequent analysis while ensuring their integrity and quality at all times. 

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